mariadb/storage/innobase/btr/btr0cur.c

/*****************************************************************************

Copyright (c) 1994, 2013, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2008, Google Inc.

Portions of this file contain modifications contributed and copyrighted by
Google, Inc. Those modifications are gratefully acknowledged and are described
briefly in the InnoDB documentation. The contributions by Google are
incorporated with their permission, and subject to the conditions contained in
the file COPYING.Google.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file btr/btr0cur.c
The index tree cursor

All changes that row operations make to a B-tree or the records
there must go through this module! Undo log records are written here
of every modify or insert of a clustered index record.

			NOTE!!!
To make sure we do not run out of disk space during a pessimistic
insert or update, we have to reserve 2 x the height of the index tree
many pages in the tablespace before we start the operation, because
if leaf splitting has been started, it is difficult to undo, except
by crashing the database and doing a roll-forward.

Created 10/16/1994 Heikki Tuuri
*******************************************************/

#include "btr0cur.h"

#ifdef UNIV_NONINL
#include "btr0cur.ic"
#endif

#include "row0upd.h"
#ifndef UNIV_HOTBACKUP
#include "mtr0log.h"
#include "page0page.h"
#include "page0zip.h"
#include "rem0rec.h"
#include "rem0cmp.h"
#include "buf0lru.h"
#include "btr0btr.h"
#include "btr0sea.h"
#include "row0purge.h"
#include "row0upd.h"
#include "trx0rec.h"
#include "trx0roll.h" /* trx_is_recv() */
#include "que0que.h"
#include "row0row.h"
#include "srv0srv.h"
#include "ibuf0ibuf.h"
#include "lock0lock.h"
#include "zlib.h"

/** Buffered B-tree operation types, introduced as part of delete buffering. */
typedef enum btr_op_enum {
	BTR_NO_OP = 0,			/*!< Not buffered */
	BTR_INSERT_OP,			/*!< Insert, do not ignore UNIQUE */
	BTR_INSERT_IGNORE_UNIQUE_OP,	/*!< Insert, ignoring UNIQUE */
	BTR_DELETE_OP,			/*!< Purge a delete-marked record */
	BTR_DELMARK_OP			/*!< Mark a record for deletion */
} btr_op_t;

#ifdef UNIV_DEBUG
/** If the following is set to TRUE, this module prints a lot of
trace information of individual record operations */
UNIV_INTERN ibool	btr_cur_print_record_ops = FALSE;
#endif /* UNIV_DEBUG */

/** Number of searches down the B-tree in btr_cur_search_to_nth_level(). */
UNIV_INTERN ulint	btr_cur_n_non_sea	= 0;
/** Number of successful adaptive hash index lookups in
btr_cur_search_to_nth_level(). */
UNIV_INTERN ulint	btr_cur_n_sea		= 0;
/** Old value of btr_cur_n_non_sea.  Copied by
srv_refresh_innodb_monitor_stats().  Referenced by
srv_printf_innodb_monitor(). */
UNIV_INTERN ulint	btr_cur_n_non_sea_old	= 0;
/** Old value of btr_cur_n_sea.  Copied by
srv_refresh_innodb_monitor_stats().  Referenced by
srv_printf_innodb_monitor(). */
UNIV_INTERN ulint	btr_cur_n_sea_old	= 0;

#ifdef UNIV_DEBUG
/* Flag to limit optimistic insert records */
UNIV_INTERN uint	btr_cur_limit_optimistic_insert_debug = 0;
#endif /* UNIV_DEBUG */

/** In the optimistic insert, if the insert does not fit, but this much space
can be released by page reorganize, then it is reorganized */
#define BTR_CUR_PAGE_REORGANIZE_LIMIT	(UNIV_PAGE_SIZE / 32)

/** The structure of a BLOB part header */
/* @{ */
/*--------------------------------------*/
#define BTR_BLOB_HDR_PART_LEN		0	/*!< BLOB part len on this
						page */
#define BTR_BLOB_HDR_NEXT_PAGE_NO	4	/*!< next BLOB part page no,
						FIL_NULL if none */
/*--------------------------------------*/
#define BTR_BLOB_HDR_SIZE		8	/*!< Size of a BLOB
						part header, in bytes */

/** Estimated table level stats from sampled value.
@param value		sampled stats
@param index		index being sampled
@param sample		number of sampled rows
@param ext_size		external stored data size
@param not_empty	table not empty
@return estimated table wide stats from sampled value */
#define BTR_TABLE_STATS_FROM_SAMPLE(value, index, sample, ext_size, not_empty)\
	(((value) * (ib_int64_t) index->stat_n_leaf_pages		\
	  + (sample) - 1 + (ext_size) + (not_empty)) / ((sample) + (ext_size)))

/* @} */
#endif /* !UNIV_HOTBACKUP */

/** A BLOB field reference full of zero, for use in assertions and tests.
Initially, BLOB field references are set to zero, in
dtuple_convert_big_rec(). */
UNIV_INTERN const byte field_ref_zero[BTR_EXTERN_FIELD_REF_SIZE];

#ifndef UNIV_HOTBACKUP
/*******************************************************************//**
Marks all extern fields in a record as owned by the record. This function
should be called if the delete mark of a record is removed: a not delete
marked record always owns all its extern fields. */
static
void
btr_cur_unmark_extern_fields(
/*=========================*/
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose uncompressed
				part will be updated, or NULL */
	rec_t*		rec,	/*!< in/out: record in a clustered index */
	dict_index_t*	index,	/*!< in: index of the page */
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	mtr_t*		mtr);	/*!< in: mtr, or NULL if not logged */
/*******************************************************************//**
Adds path information to the cursor for the current page, for which
the binary search has been performed. */
static
void
btr_cur_add_path_info(
/*==================*/
	btr_cur_t*	cursor,		/*!< in: cursor positioned on a page */
	ulint		height,		/*!< in: height of the page in tree;
					0 means leaf node */
	ulint		root_height);	/*!< in: root node height in tree */
/***********************************************************//**
Frees the externally stored fields for a record, if the field is mentioned
in the update vector. */
static
void
btr_rec_free_updated_extern_fields(
/*===============================*/
	dict_index_t*	index,	/*!< in: index of rec; the index tree MUST be
				X-latched */
	rec_t*		rec,	/*!< in: record */
	page_zip_des_t*	page_zip,/*!< in: compressed page whose uncompressed
				part will be updated, or NULL */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec, index) */
	const upd_t*	update,	/*!< in: update vector */
	enum trx_rb_ctx	rb_ctx,	/*!< in: rollback context */
	mtr_t*		mtr);	/*!< in: mini-transaction handle which contains
				an X-latch to record page and to the tree */
/***********************************************************//**
Frees the externally stored fields for a record. */
static
void
btr_rec_free_externally_stored_fields(
/*==================================*/
	dict_index_t*	index,	/*!< in: index of the data, the index
				tree MUST be X-latched */
	rec_t*		rec,	/*!< in: record */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec, index) */
	page_zip_des_t*	page_zip,/*!< in: compressed page whose uncompressed
				part will be updated, or NULL */
	enum trx_rb_ctx	rb_ctx,	/*!< in: rollback context */
	mtr_t*		mtr);	/*!< in: mini-transaction handle which contains
				an X-latch to record page and to the index
				tree */
/***********************************************************//**
Gets the externally stored size of a record, in units of a database page.
@return	externally stored part, in units of a database page */
static
ulint
btr_rec_get_externally_stored_len(
/*==============================*/
	const rec_t*	rec,	/*!< in: record */
	const ulint*	offsets);/*!< in: array returned by rec_get_offsets() */
#endif /* !UNIV_HOTBACKUP */

/******************************************************//**
The following function is used to set the deleted bit of a record. */
UNIV_INLINE
void
btr_rec_set_deleted_flag(
/*=====================*/
	rec_t*		rec,	/*!< in/out: physical record */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page (or NULL) */
	ulint		flag)	/*!< in: nonzero if delete marked */
{
	if (page_rec_is_comp(rec)) {
		rec_set_deleted_flag_new(rec, page_zip, flag);
	} else {
		ut_ad(!page_zip);
		rec_set_deleted_flag_old(rec, flag);
	}
}

#ifndef UNIV_HOTBACKUP
/*==================== B-TREE SEARCH =========================*/

/********************************************************************//**
Latches the leaf page or pages requested. */
static
void
btr_cur_latch_leaves(
/*=================*/
	page_t*		page,		/*!< in: leaf page where the search
					converged */
	ulint		space,		/*!< in: space id */
	ulint		zip_size,	/*!< in: compressed page size in bytes
					or 0 for uncompressed pages */
	ulint		page_no,	/*!< in: page number of the leaf */
	ulint		latch_mode,	/*!< in: BTR_SEARCH_LEAF, ... */
	btr_cur_t*	cursor,		/*!< in: cursor */
	mtr_t*		mtr)		/*!< in: mtr */
{
	ulint		mode;
	ulint		left_page_no;
	ulint		right_page_no;
	buf_block_t*	get_block;

	ut_ad(page && mtr);

	switch (latch_mode) {
	case BTR_SEARCH_LEAF:
	case BTR_MODIFY_LEAF:
		mode = latch_mode == BTR_SEARCH_LEAF ? RW_S_LATCH : RW_X_LATCH;
		get_block = btr_block_get(
			space, zip_size, page_no, mode, cursor->index, mtr);
#ifdef UNIV_BTR_DEBUG
		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
#endif /* UNIV_BTR_DEBUG */
		get_block->check_index_page_at_flush = TRUE;
		return;
	case BTR_MODIFY_TREE:
		/* x-latch also brothers from left to right */
		left_page_no = btr_page_get_prev(page, mtr);

		if (left_page_no != FIL_NULL) {
			get_block = btr_block_get(
				space, zip_size, left_page_no,
				RW_X_LATCH, cursor->index, mtr);
#ifdef UNIV_BTR_DEBUG
			ut_a(page_is_comp(get_block->frame)
			     == page_is_comp(page));
			ut_a(btr_page_get_next(get_block->frame, mtr)
			     == page_get_page_no(page));
#endif /* UNIV_BTR_DEBUG */
			get_block->check_index_page_at_flush = TRUE;
		}

		get_block = btr_block_get(
			space, zip_size, page_no,
			RW_X_LATCH, cursor->index, mtr);
#ifdef UNIV_BTR_DEBUG
		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
#endif /* UNIV_BTR_DEBUG */
		get_block->check_index_page_at_flush = TRUE;

		right_page_no = btr_page_get_next(page, mtr);

		if (right_page_no != FIL_NULL) {
			get_block = btr_block_get(
				space, zip_size, right_page_no,
				RW_X_LATCH, cursor->index, mtr);
#ifdef UNIV_BTR_DEBUG
			ut_a(page_is_comp(get_block->frame)
			     == page_is_comp(page));
			ut_a(btr_page_get_prev(get_block->frame, mtr)
			     == page_get_page_no(page));
#endif /* UNIV_BTR_DEBUG */
			get_block->check_index_page_at_flush = TRUE;
		}

		return;

	case BTR_SEARCH_PREV:
	case BTR_MODIFY_PREV:
		mode = latch_mode == BTR_SEARCH_PREV ? RW_S_LATCH : RW_X_LATCH;
		/* latch also left brother */
		left_page_no = btr_page_get_prev(page, mtr);

		if (left_page_no != FIL_NULL) {
			get_block = btr_block_get(
				space, zip_size,
				left_page_no, mode, cursor->index, mtr);
			cursor->left_block = get_block;
#ifdef UNIV_BTR_DEBUG
			ut_a(page_is_comp(get_block->frame)
			     == page_is_comp(page));
			ut_a(btr_page_get_next(get_block->frame, mtr)
			     == page_get_page_no(page));
#endif /* UNIV_BTR_DEBUG */
			get_block->check_index_page_at_flush = TRUE;
		}

		get_block = btr_block_get(
			space, zip_size, page_no, mode, cursor->index, mtr);
#ifdef UNIV_BTR_DEBUG
		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
#endif /* UNIV_BTR_DEBUG */
		get_block->check_index_page_at_flush = TRUE;
		return;
	}

	ut_error;
}

/********************************************************************//**
Searches an index tree and positions a tree cursor on a given level.
NOTE: n_fields_cmp in tuple must be set so that it cannot be compared
to node pointer page number fields on the upper levels of the tree!
Note that if mode is PAGE_CUR_LE, which is used in inserts, then
cursor->up_match and cursor->low_match both will have sensible values.
If mode is PAGE_CUR_GE, then up_match will a have a sensible value.

If mode is PAGE_CUR_LE , cursor is left at the place where an insert of the
search tuple should be performed in the B-tree. InnoDB does an insert
immediately after the cursor. Thus, the cursor may end up on a user record,
or on a page infimum record. */
UNIV_INTERN
void
btr_cur_search_to_nth_level(
/*========================*/
	dict_index_t*	index,	/*!< in: index */
	ulint		level,	/*!< in: the tree level of search */
	const dtuple_t*	tuple,	/*!< in: data tuple; NOTE: n_fields_cmp in
				tuple must be set so that it cannot get
				compared to the node ptr page number field! */
	ulint		mode,	/*!< in: PAGE_CUR_L, ...;
				Inserts should always be made using
				PAGE_CUR_LE to search the position! */
	ulint		latch_mode, /*!< in: BTR_SEARCH_LEAF, ..., ORed with
				at most one of BTR_INSERT, BTR_DELETE_MARK,
				BTR_DELETE, or BTR_ESTIMATE;
				cursor->left_block is used to store a pointer
				to the left neighbor page, in the cases
				BTR_SEARCH_PREV and BTR_MODIFY_PREV;
				NOTE that if has_search_latch
				is != 0, we maybe do not have a latch set
				on the cursor page, we assume
				the caller uses his search latch
				to protect the record! */
	btr_cur_t*	cursor, /*!< in/out: tree cursor; the cursor page is
				s- or x-latched, but see also above! */
	ulint		has_search_latch,/*!< in: info on the latch mode the
				caller currently has on btr_search_latch:
				RW_S_LATCH, or 0 */
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line where called */
	mtr_t*		mtr)	/*!< in: mtr */
{
	page_t*		page;
	buf_block_t*	block;
	ulint		space;
	buf_block_t*	guess;
	ulint		height;
	ulint		page_no;
	ulint		up_match;
	ulint		up_bytes;
	ulint		low_match;
	ulint		low_bytes;
	ulint		savepoint;
	ulint		rw_latch;
	ulint		page_mode;
	ulint		buf_mode;
	ulint		estimate;
	ulint		zip_size;
	page_cur_t*	page_cursor;
	btr_op_t	btr_op;
	ulint		root_height = 0; /* remove warning */

#ifdef BTR_CUR_ADAPT
	btr_search_t*	info;
#endif
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	rec_offs_init(offsets_);
	/* Currently, PAGE_CUR_LE is the only search mode used for searches
	ending to upper levels */

	ut_ad(level == 0 || mode == PAGE_CUR_LE);
	ut_ad(dict_index_check_search_tuple(index, tuple));
	ut_ad(!dict_index_is_ibuf(index) || ibuf_inside(mtr));
	ut_ad(dtuple_check_typed(tuple));
	ut_ad(index->page != FIL_NULL);

	UNIV_MEM_INVALID(&cursor->up_match, sizeof cursor->up_match);
	UNIV_MEM_INVALID(&cursor->up_bytes, sizeof cursor->up_bytes);
	UNIV_MEM_INVALID(&cursor->low_match, sizeof cursor->low_match);
	UNIV_MEM_INVALID(&cursor->low_bytes, sizeof cursor->low_bytes);
#ifdef UNIV_DEBUG
	cursor->up_match = ULINT_UNDEFINED;
	cursor->low_match = ULINT_UNDEFINED;
#endif

	/* These flags are mutually exclusive, they are lumped together
	with the latch mode for historical reasons. It's possible for
	none of the flags to be set. */
	switch (UNIV_EXPECT(latch_mode
			    & (BTR_INSERT | BTR_DELETE | BTR_DELETE_MARK),
			    0)) {
	case 0:
		btr_op = BTR_NO_OP;
		break;
	case BTR_INSERT:
		btr_op = (latch_mode & BTR_IGNORE_SEC_UNIQUE)
			? BTR_INSERT_IGNORE_UNIQUE_OP
			: BTR_INSERT_OP;
		break;
	case BTR_DELETE:
		btr_op = BTR_DELETE_OP;
		ut_a(cursor->purge_node);
		break;
	case BTR_DELETE_MARK:
		btr_op = BTR_DELMARK_OP;
		break;
	default:
		/* only one of BTR_INSERT, BTR_DELETE, BTR_DELETE_MARK
		should be specified at a time */
		ut_error;
	}

	/* Operations on the insert buffer tree cannot be buffered. */
	ut_ad(btr_op == BTR_NO_OP || !dict_index_is_ibuf(index));
	/* Operations on the clustered index cannot be buffered. */
	ut_ad(btr_op == BTR_NO_OP || !dict_index_is_clust(index));

	estimate = latch_mode & BTR_ESTIMATE;

	/* Turn the flags unrelated to the latch mode off. */
	latch_mode &= ~(BTR_INSERT
			| BTR_DELETE_MARK
			| BTR_DELETE
			| BTR_ESTIMATE
			| BTR_IGNORE_SEC_UNIQUE);

	cursor->flag = BTR_CUR_BINARY;
	cursor->index = index;

#ifndef BTR_CUR_ADAPT
	guess = NULL;
#else
	info = btr_search_get_info(index);

	guess = info->root_guess;

#ifdef BTR_CUR_HASH_ADAPT

#ifdef UNIV_SEARCH_PERF_STAT
	info->n_searches++;
#endif
	if (rw_lock_get_writer(&btr_search_latch) == RW_LOCK_NOT_LOCKED
	    && latch_mode <= BTR_MODIFY_LEAF
	    && info->last_hash_succ
	    && !estimate
#ifdef PAGE_CUR_LE_OR_EXTENDS
	    && mode != PAGE_CUR_LE_OR_EXTENDS
#endif /* PAGE_CUR_LE_OR_EXTENDS */
	    /* If !has_search_latch, we do a dirty read of
	    btr_search_enabled below, and btr_search_guess_on_hash()
	    will have to check it again. */
	    && UNIV_LIKELY(btr_search_enabled)
	    && btr_search_guess_on_hash(index, info, tuple, mode,
					latch_mode, cursor,
					has_search_latch, mtr)) {

		/* Search using the hash index succeeded */

		ut_ad(cursor->up_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_GE);
		ut_ad(cursor->up_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_LE);
		ut_ad(cursor->low_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_LE);
		btr_cur_n_sea++;

		return;
	}
#endif /* BTR_CUR_HASH_ADAPT */
#endif /* BTR_CUR_ADAPT */
	btr_cur_n_non_sea++;

	/* If the hash search did not succeed, do binary search down the
	tree */

	if (has_search_latch) {
		/* Release possible search latch to obey latching order */
		rw_lock_s_unlock(&btr_search_latch);
	}

	/* Store the position of the tree latch we push to mtr so that we
	know how to release it when we have latched leaf node(s) */

	savepoint = mtr_set_savepoint(mtr);

	if (latch_mode == BTR_MODIFY_TREE) {
		mtr_x_lock(dict_index_get_lock(index), mtr);

	} else if (latch_mode == BTR_CONT_MODIFY_TREE) {
		/* Do nothing */
		ut_ad(mtr_memo_contains(mtr, dict_index_get_lock(index),
					MTR_MEMO_X_LOCK));
	} else {
		mtr_s_lock(dict_index_get_lock(index), mtr);
	}

	page_cursor = btr_cur_get_page_cur(cursor);

	space = dict_index_get_space(index);
	page_no = dict_index_get_page(index);

	up_match = 0;
	up_bytes = 0;
	low_match = 0;
	low_bytes = 0;

	height = ULINT_UNDEFINED;

	/* We use these modified search modes on non-leaf levels of the
	B-tree. These let us end up in the right B-tree leaf. In that leaf
	we use the original search mode. */

	switch (mode) {
	case PAGE_CUR_GE:
		page_mode = PAGE_CUR_L;
		break;
	case PAGE_CUR_G:
		page_mode = PAGE_CUR_LE;
		break;
	default:
#ifdef PAGE_CUR_LE_OR_EXTENDS
		ut_ad(mode == PAGE_CUR_L || mode == PAGE_CUR_LE
		      || mode == PAGE_CUR_LE_OR_EXTENDS);
#else /* PAGE_CUR_LE_OR_EXTENDS */
		ut_ad(mode == PAGE_CUR_L || mode == PAGE_CUR_LE);
#endif /* PAGE_CUR_LE_OR_EXTENDS */
		page_mode = mode;
		break;
	}

	/* Loop and search until we arrive at the desired level */

search_loop:
	buf_mode = BUF_GET;
	rw_latch = RW_NO_LATCH;

	if (height != 0) {
		/* We are about to fetch the root or a non-leaf page. */
	} else if (latch_mode <= BTR_MODIFY_LEAF) {
		rw_latch = latch_mode;

		if (btr_op != BTR_NO_OP
		    && ibuf_should_try(index, btr_op != BTR_INSERT_OP)) {

			/* Try to buffer the operation if the leaf
			page is not in the buffer pool. */

			buf_mode = btr_op == BTR_DELETE_OP
				? BUF_GET_IF_IN_POOL_OR_WATCH
				: BUF_GET_IF_IN_POOL;
		}
	}

	zip_size = dict_table_zip_size(index->table);

retry_page_get:
	block = buf_page_get_gen(
		space, zip_size, page_no, rw_latch, guess, buf_mode,
		file, line, mtr);

	if (block == NULL) {
		/* This must be a search to perform an insert/delete
		mark/ delete; try using the insert/delete buffer */

		ut_ad(height == 0);
		ut_ad(cursor->thr);

		switch (btr_op) {
		case BTR_INSERT_OP:
		case BTR_INSERT_IGNORE_UNIQUE_OP:
			ut_ad(buf_mode == BUF_GET_IF_IN_POOL);

			if (ibuf_insert(IBUF_OP_INSERT, tuple, index,
					space, zip_size, page_no,
					cursor->thr)) {

				cursor->flag = BTR_CUR_INSERT_TO_IBUF;

				goto func_exit;
			}
			break;

		case BTR_DELMARK_OP:
			ut_ad(buf_mode == BUF_GET_IF_IN_POOL);

			if (ibuf_insert(IBUF_OP_DELETE_MARK, tuple,
					index, space, zip_size,
					page_no, cursor->thr)) {

				cursor->flag = BTR_CUR_DEL_MARK_IBUF;

				goto func_exit;
			}

			break;

		case BTR_DELETE_OP:
			ut_ad(buf_mode == BUF_GET_IF_IN_POOL_OR_WATCH);

			if (!row_purge_poss_sec(cursor->purge_node,
						index, tuple)) {

				/* The record cannot be purged yet. */
				cursor->flag = BTR_CUR_DELETE_REF;
			} else if (ibuf_insert(IBUF_OP_DELETE, tuple,
					       index, space, zip_size,
					       page_no,
					       cursor->thr)) {

				/* The purge was buffered. */
				cursor->flag = BTR_CUR_DELETE_IBUF;
			} else {
				/* The purge could not be buffered. */
				buf_pool_watch_unset(space, page_no);
				break;
			}

			buf_pool_watch_unset(space, page_no);
			goto func_exit;

		default:
			ut_error;
		}

		/* Insert to the insert/delete buffer did not succeed, we
		must read the page from disk. */

		buf_mode = BUF_GET;

		goto retry_page_get;
	}

	block->check_index_page_at_flush = TRUE;
	page = buf_block_get_frame(block);

	if (rw_latch != RW_NO_LATCH) {
#ifdef UNIV_ZIP_DEBUG
		const page_zip_des_t*	page_zip
			= buf_block_get_page_zip(block);
		ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */

		buf_block_dbg_add_level(
			block, dict_index_is_ibuf(index)
			? SYNC_IBUF_TREE_NODE : SYNC_TREE_NODE);
	}

	ut_ad(index->id == btr_page_get_index_id(page));

	if (UNIV_UNLIKELY(height == ULINT_UNDEFINED)) {
		/* We are in the root node */

		height = btr_page_get_level(page, mtr);
		root_height = height;
		cursor->tree_height = root_height + 1;

#ifdef BTR_CUR_ADAPT
		if (block != guess) {
			info->root_guess = block;
		}
#endif
	}

	if (height == 0) {
		if (rw_latch == RW_NO_LATCH) {

			btr_cur_latch_leaves(
				page, space, zip_size, page_no, latch_mode,
				cursor, mtr);
		}

		if (latch_mode != BTR_MODIFY_TREE
		    && latch_mode != BTR_CONT_MODIFY_TREE) {

			/* Release the tree s-latch */

			mtr_release_s_latch_at_savepoint(
				mtr, savepoint, dict_index_get_lock(index));
		}

		page_mode = mode;
	}

	page_cur_search_with_match(
		block, index, tuple, page_mode, &up_match, &up_bytes,
		&low_match, &low_bytes, page_cursor);

	if (estimate) {
		btr_cur_add_path_info(cursor, height, root_height);
	}

	/* If this is the desired level, leave the loop */

	ut_ad(height == btr_page_get_level(page_cur_get_page(page_cursor),
					   mtr));

	if (level != height) {

		const rec_t*	node_ptr;
		ut_ad(height > 0);

		height--;
		guess = NULL;

		node_ptr = page_cur_get_rec(page_cursor);

		offsets = rec_get_offsets(
			node_ptr, index, offsets, ULINT_UNDEFINED, &heap);

		/* Go to the child node */
		page_no = btr_node_ptr_get_child_page_no(node_ptr, offsets);

		if (UNIV_UNLIKELY(height == 0 && dict_index_is_ibuf(index))) {
			/* We're doing a search on an ibuf tree and we're one
			level above the leaf page. */

			ut_ad(level == 0);

			buf_mode = BUF_GET;
			rw_latch = RW_NO_LATCH;
			goto retry_page_get;
		}

		goto search_loop;
	}

	if (level != 0) {
		/* x-latch the page */
		buf_block_t*	child_block = btr_block_get(
			space, zip_size, page_no, RW_X_LATCH, index, mtr);

		page = buf_block_get_frame(child_block);
		btr_assert_not_corrupted(child_block, index);
	} else {
		cursor->low_match = low_match;
		cursor->low_bytes = low_bytes;
		cursor->up_match = up_match;
		cursor->up_bytes = up_bytes;

#ifdef BTR_CUR_ADAPT
		/* We do a dirty read of btr_search_enabled here.  We
		will properly check btr_search_enabled again in
		btr_search_build_page_hash_index() before building a
		page hash index, while holding btr_search_latch. */
		if (UNIV_LIKELY(btr_search_enabled)) {

			btr_search_info_update(index, cursor);
		}
#endif
		ut_ad(cursor->up_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_GE);
		ut_ad(cursor->up_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_LE);
		ut_ad(cursor->low_match != ULINT_UNDEFINED
		      || mode != PAGE_CUR_LE);
	}

func_exit:

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}

	if (has_search_latch) {

		rw_lock_s_lock(&btr_search_latch);
	}
}

/*****************************************************************//**
Opens a cursor at either end of an index. */
UNIV_INTERN
void
btr_cur_open_at_index_side_func(
/*============================*/
	ibool		from_left,	/*!< in: TRUE if open to the low end,
					FALSE if to the high end */
	dict_index_t*	index,		/*!< in: index */
	ulint		latch_mode,	/*!< in: latch mode */
	btr_cur_t*	cursor,		/*!< in: cursor */
	const char*	file,		/*!< in: file name */
	ulint		line,		/*!< in: line where called */
	mtr_t*		mtr)		/*!< in: mtr */
{
	page_cur_t*	page_cursor;
	ulint		page_no;
	ulint		space;
	ulint		zip_size;
	ulint		height;
	ulint		root_height = 0; /* remove warning */
	rec_t*		node_ptr;
	ulint		estimate;
	ulint		savepoint;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	rec_offs_init(offsets_);

	estimate = latch_mode & BTR_ESTIMATE;
	latch_mode = latch_mode & ~BTR_ESTIMATE;

	/* Store the position of the tree latch we push to mtr so that we
	know how to release it when we have latched the leaf node */

	savepoint = mtr_set_savepoint(mtr);

	if (latch_mode == BTR_MODIFY_TREE) {
		mtr_x_lock(dict_index_get_lock(index), mtr);
	} else {
		mtr_s_lock(dict_index_get_lock(index), mtr);
	}

	page_cursor = btr_cur_get_page_cur(cursor);
	cursor->index = index;

	space = dict_index_get_space(index);
	zip_size = dict_table_zip_size(index->table);
	page_no = dict_index_get_page(index);

	height = ULINT_UNDEFINED;

	for (;;) {
		buf_block_t*	block;
		page_t*		page;
		block = buf_page_get_gen(space, zip_size, page_no,
					 RW_NO_LATCH, NULL, BUF_GET,
					 file, line, mtr);
		page = buf_block_get_frame(block);
		ut_ad(index->id == btr_page_get_index_id(page));

		block->check_index_page_at_flush = TRUE;

		if (height == ULINT_UNDEFINED) {
			/* We are in the root node */

			height = btr_page_get_level(page, mtr);
			root_height = height;
		}

		if (height == 0) {
			btr_cur_latch_leaves(page, space, zip_size, page_no,
					     latch_mode, cursor, mtr);

			/* In versions <= 3.23.52 we had forgotten to
			release the tree latch here. If in an index scan
			we had to scan far to find a record visible to the
			current transaction, that could starve others
			waiting for the tree latch. */

			if ((latch_mode != BTR_MODIFY_TREE)
			    && (latch_mode != BTR_CONT_MODIFY_TREE)) {

				/* Release the tree s-latch */

				mtr_release_s_latch_at_savepoint(
					mtr, savepoint,
					dict_index_get_lock(index));
			}
		}

		if (from_left) {
			page_cur_set_before_first(block, page_cursor);
		} else {
			page_cur_set_after_last(block, page_cursor);
		}

		if (height == 0) {
			if (estimate) {
				btr_cur_add_path_info(cursor, height,
						      root_height);
			}

			break;
		}

		ut_ad(height > 0);

		if (from_left) {
			page_cur_move_to_next(page_cursor);
		} else {
			page_cur_move_to_prev(page_cursor);
		}

		if (estimate) {
			btr_cur_add_path_info(cursor, height, root_height);
		}

		height--;

		node_ptr = page_cur_get_rec(page_cursor);
		offsets = rec_get_offsets(node_ptr, cursor->index, offsets,
					  ULINT_UNDEFINED, &heap);
		/* Go to the child node */
		page_no = btr_node_ptr_get_child_page_no(node_ptr, offsets);
	}

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}
}

/**********************************************************************//**
Positions a cursor at a randomly chosen position within a B-tree. */
UNIV_INTERN
void
btr_cur_open_at_rnd_pos_func(
/*=========================*/
	dict_index_t*	index,		/*!< in: index */
	ulint		latch_mode,	/*!< in: BTR_SEARCH_LEAF, ... */
	btr_cur_t*	cursor,		/*!< in/out: B-tree cursor */
	const char*	file,		/*!< in: file name */
	ulint		line,		/*!< in: line where called */
	mtr_t*		mtr)		/*!< in: mtr */
{
	page_cur_t*	page_cursor;
	ulint		page_no;
	ulint		space;
	ulint		zip_size;
	ulint		height;
	rec_t*		node_ptr;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	rec_offs_init(offsets_);

	if (latch_mode == BTR_MODIFY_TREE) {
		mtr_x_lock(dict_index_get_lock(index), mtr);
	} else {
		mtr_s_lock(dict_index_get_lock(index), mtr);
	}

	page_cursor = btr_cur_get_page_cur(cursor);
	cursor->index = index;

	space = dict_index_get_space(index);
	zip_size = dict_table_zip_size(index->table);
	page_no = dict_index_get_page(index);

	height = ULINT_UNDEFINED;

	for (;;) {
		buf_block_t*	block;
		page_t*		page;

		block = buf_page_get_gen(space, zip_size, page_no,
					 RW_NO_LATCH, NULL, BUF_GET,
					 file, line, mtr);
		page = buf_block_get_frame(block);
		ut_ad(index->id == btr_page_get_index_id(page));

		if (height == ULINT_UNDEFINED) {
			/* We are in the root node */

			height = btr_page_get_level(page, mtr);
		}

		if (height == 0) {
			btr_cur_latch_leaves(page, space, zip_size, page_no,
					     latch_mode, cursor, mtr);
		}

		page_cur_open_on_rnd_user_rec(block, page_cursor);

		if (height == 0) {

			break;
		}

		ut_ad(height > 0);

		height--;

		node_ptr = page_cur_get_rec(page_cursor);
		offsets = rec_get_offsets(node_ptr, cursor->index, offsets,
					  ULINT_UNDEFINED, &heap);
		/* Go to the child node */
		page_no = btr_node_ptr_get_child_page_no(node_ptr, offsets);
	}

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}
}

/*==================== B-TREE INSERT =========================*/

/*************************************************************//**
Inserts a record if there is enough space, or if enough space can
be freed by reorganizing. Differs from btr_cur_optimistic_insert because
no heuristics is applied to whether it pays to use CPU time for
reorganizing the page or not.
@return	pointer to inserted record if succeed, else NULL */
static
rec_t*
btr_cur_insert_if_possible(
/*=======================*/
	btr_cur_t*	cursor,	/*!< in: cursor on page after which to insert;
				cursor stays valid */
	const dtuple_t*	tuple,	/*!< in: tuple to insert; the size info need not
				have been stored to tuple */
	ulint		n_ext,	/*!< in: number of externally stored columns */
	mtr_t*		mtr)	/*!< in: mtr */
{
	page_cur_t*	page_cursor;
	buf_block_t*	block;
	rec_t*		rec;

	ut_ad(dtuple_check_typed(tuple));

	block = btr_cur_get_block(cursor);

	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	page_cursor = btr_cur_get_page_cur(cursor);

	/* Now, try the insert */
	rec = page_cur_tuple_insert(page_cursor, tuple,
				    cursor->index, n_ext, mtr);

	if (UNIV_UNLIKELY(!rec)) {
		/* If record did not fit, reorganize */

		if (btr_page_reorganize(block, cursor->index, mtr)) {

			page_cur_search(block, cursor->index, tuple,
					PAGE_CUR_LE, page_cursor);

			rec = page_cur_tuple_insert(page_cursor, tuple,
						    cursor->index, n_ext, mtr);
		}
	}

	return(rec);
}

/*************************************************************//**
For an insert, checks the locks and does the undo logging if desired.
@return	DB_SUCCESS, DB_WAIT_LOCK, DB_FAIL, or error number */
UNIV_INLINE
ulint
btr_cur_ins_lock_and_undo(
/*======================*/
	ulint		flags,	/*!< in: undo logging and locking flags: if
				not zero, the parameters index and thr
				should be specified */
	btr_cur_t*	cursor,	/*!< in: cursor on page after which to insert */
	dtuple_t*	entry,	/*!< in/out: entry to insert */
	que_thr_t*	thr,	/*!< in: query thread or NULL */
	mtr_t*		mtr,	/*!< in/out: mini-transaction */
	ibool*		inherit)/*!< out: TRUE if the inserted new record maybe
				should inherit LOCK_GAP type locks from the
				successor record */
{
	dict_index_t*	index;
	ulint		err;
	rec_t*		rec;
	roll_ptr_t	roll_ptr;

	/* Check if we have to wait for a lock: enqueue an explicit lock
	request if yes */

	rec = btr_cur_get_rec(cursor);
	index = cursor->index;

	err = lock_rec_insert_check_and_lock(flags, rec,
					     btr_cur_get_block(cursor),
					     index, thr, mtr, inherit);

	if (err != DB_SUCCESS) {

		return(err);
	}

	if (dict_index_is_clust(index) && !dict_index_is_ibuf(index)) {

		err = trx_undo_report_row_operation(flags, TRX_UNDO_INSERT_OP,
						    thr, index, entry,
						    NULL, 0, NULL,
						    &roll_ptr);
		if (err != DB_SUCCESS) {

			return(err);
		}

		/* Now we can fill in the roll ptr field in entry */

		if (!(flags & BTR_KEEP_SYS_FLAG)) {

			row_upd_index_entry_sys_field(entry, index,
						      DATA_ROLL_PTR, roll_ptr);
		}
	}

	return(DB_SUCCESS);
}

#ifdef UNIV_DEBUG
/*************************************************************//**
Report information about a transaction. */
static
void
btr_cur_trx_report(
/*===============*/
	trx_t*			trx,	/*!< in: transaction */
	const dict_index_t*	index,	/*!< in: index */
	const char*		op)	/*!< in: operation */
{
	fprintf(stderr, "Trx with id " TRX_ID_FMT " going to ",
		(ullint) trx->id);
	fputs(op, stderr);
	dict_index_name_print(stderr, trx, index);
	putc('\n', stderr);
}
#endif /* UNIV_DEBUG */

/*************************************************************//**
Tries to perform an insert to a page in an index tree, next to cursor.
It is assumed that mtr holds an x-latch on the page. The operation does
not succeed if there is too little space on the page. If there is just
one record on the page, the insert will always succeed; this is to
prevent trying to split a page with just one record.
@return	DB_SUCCESS, DB_WAIT_LOCK, DB_FAIL, or error number */
UNIV_INTERN
ulint
btr_cur_optimistic_insert(
/*======================*/
	ulint		flags,	/*!< in: undo logging and locking flags: if not
				zero, the parameters index and thr should be
				specified */
	btr_cur_t*	cursor,	/*!< in: cursor on page after which to insert;
				cursor stays valid */
	dtuple_t*	entry,	/*!< in/out: entry to insert */
	rec_t**		rec,	/*!< out: pointer to inserted record if
				succeed */
	big_rec_t**	big_rec,/*!< out: big rec vector whose fields have to
				be stored externally by the caller, or
				NULL */
	ulint		n_ext,	/*!< in: number of externally stored columns */
	que_thr_t*	thr,	/*!< in: query thread or NULL */
	mtr_t*		mtr)	/*!< in: mtr; if this function returns
				DB_SUCCESS on a leaf page of a secondary
				index in a compressed tablespace, the
				mtr must be committed before latching
				any further pages */
{
	big_rec_t*	big_rec_vec	= NULL;
	dict_index_t*	index;
	page_cur_t*	page_cursor;
	buf_block_t*	block;
	page_t*		page;
	ulint		max_size;
	rec_t*		dummy_rec;
	ibool		leaf;
	ibool		reorg;
	ibool		inherit;
	ulint		zip_size;
	ulint		rec_size;
	ulint		err;

	*big_rec = NULL;

	block = btr_cur_get_block(cursor);
	page = buf_block_get_frame(block);
	index = cursor->index;
	zip_size = buf_block_get_zip_size(block);
#ifdef UNIV_DEBUG_VALGRIND
	if (zip_size) {
		UNIV_MEM_ASSERT_RW(page, UNIV_PAGE_SIZE);
		UNIV_MEM_ASSERT_RW(block->page.zip.data, zip_size);
	}
#endif /* UNIV_DEBUG_VALGRIND */

	if (!dtuple_check_typed_no_assert(entry)) {
		fputs("InnoDB: Error in a tuple to insert into ", stderr);
		dict_index_name_print(stderr, thr_get_trx(thr), index);
	}
#ifdef UNIV_DEBUG
	if (btr_cur_print_record_ops && thr) {
		btr_cur_trx_report(thr_get_trx(thr), index, "insert into ");
		dtuple_print(stderr, entry);
	}
#endif /* UNIV_DEBUG */

	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	max_size = page_get_max_insert_size_after_reorganize(page, 1);
	leaf = page_is_leaf(page);

	/* Calculate the record size when entry is converted to a record */
	rec_size = rec_get_converted_size(index, entry, n_ext);

	if (page_zip_rec_needs_ext(rec_size, page_is_comp(page),
				   dtuple_get_n_fields(entry), zip_size)) {

		/* The record is so big that we have to store some fields
		externally on separate database pages */
		big_rec_vec = dtuple_convert_big_rec(index, entry, &n_ext);

		if (UNIV_UNLIKELY(big_rec_vec == NULL)) {

			return(DB_TOO_BIG_RECORD);
		}

		rec_size = rec_get_converted_size(index, entry, n_ext);
	}

	if (UNIV_UNLIKELY(zip_size)) {
		/* Estimate the free space of an empty compressed page.
		Subtract one byte for the encoded heap_no in the
		modification log. */
		ulint	free_space_zip = page_zip_empty_size(
			cursor->index->n_fields, zip_size);
		ulint	n_uniq = dict_index_get_n_unique_in_tree(index);

		ut_ad(dict_table_is_comp(index->table));

		if (free_space_zip == 0) {
too_big:
			if (big_rec_vec) {
				dtuple_convert_back_big_rec(
					index, entry, big_rec_vec);
			}

			return(DB_TOO_BIG_RECORD);
		}

		/* Subtract one byte for the encoded heap_no in the
		modification log. */
		free_space_zip--;

		/* There should be enough room for two node pointer
		records on an empty non-leaf page.  This prevents
		infinite page splits. */

		if (entry->n_fields >= n_uniq
		    && (REC_NODE_PTR_SIZE
			+ rec_get_converted_size_comp_prefix(
				index, entry->fields, n_uniq, NULL)
			/* On a compressed page, there is
			a two-byte entry in the dense
			page directory for every record.
			But there is no record header. */
			- (REC_N_NEW_EXTRA_BYTES - 2)
			> free_space_zip / 2)) {
			goto too_big;
		}
	}

	LIMIT_OPTIMISTIC_INSERT_DEBUG(page_get_n_recs(page),
				      goto fail);

	/* If there have been many consecutive inserts, and we are on the leaf
	level, check if we have to split the page to reserve enough free space
	for future updates of records. */

	if (dict_index_is_clust(index)
	    && (page_get_n_recs(page) >= 2)
	    && UNIV_LIKELY(leaf)
	    && (dict_index_get_space_reserve() + rec_size > max_size)
	    && (btr_page_get_split_rec_to_right(cursor, &dummy_rec)
		|| btr_page_get_split_rec_to_left(cursor, &dummy_rec))) {
fail:
		err = DB_FAIL;
fail_err:

		if (big_rec_vec) {
			dtuple_convert_back_big_rec(index, entry, big_rec_vec);
		}

		return(err);
	}

	if (UNIV_UNLIKELY(max_size < BTR_CUR_PAGE_REORGANIZE_LIMIT
			  || max_size < rec_size)
	    && UNIV_LIKELY(page_get_n_recs(page) > 1)
	    && page_get_max_insert_size(page, 1) < rec_size) {

		goto fail;
	}

	/* Check locks and write to the undo log, if specified */
	err = btr_cur_ins_lock_and_undo(flags, cursor, entry,
					thr, mtr, &inherit);

	if (UNIV_UNLIKELY(err != DB_SUCCESS)) {

		goto fail_err;
	}

	page_cursor = btr_cur_get_page_cur(cursor);

	/* Now, try the insert */

	{
		const rec_t* page_cursor_rec = page_cur_get_rec(page_cursor);
		*rec = page_cur_tuple_insert(page_cursor, entry, index,
					     n_ext, mtr);
		reorg = page_cursor_rec != page_cur_get_rec(page_cursor);

		if (UNIV_UNLIKELY(reorg)) {
			ut_a(zip_size);
			/* It's possible for rec to be NULL if the
			page is compressed.  This is because a
			reorganized page may become incompressible. */
			if (!*rec) {
				goto fail;
			}
		}
	}

	if (UNIV_UNLIKELY(!*rec) && UNIV_LIKELY(!reorg)) {
		/* If the record did not fit, reorganize */
		if (UNIV_UNLIKELY(!btr_page_reorganize(block, index, mtr))) {
			ut_a(zip_size);

			goto fail;
		}

		ut_ad(zip_size
		      || page_get_max_insert_size(page, 1) == max_size);

		reorg = TRUE;

		page_cur_search(block, index, entry, PAGE_CUR_LE, page_cursor);

		*rec = page_cur_tuple_insert(page_cursor, entry, index,
					     n_ext, mtr);

		if (UNIV_UNLIKELY(!*rec)) {
			if (UNIV_LIKELY(zip_size != 0)) {

				goto fail;
			}

			fputs("InnoDB: Error: cannot insert tuple ", stderr);
			dtuple_print(stderr, entry);
			fputs(" into ", stderr);
			dict_index_name_print(stderr, thr_get_trx(thr), index);
			fprintf(stderr, "\nInnoDB: max insert size %lu\n",
				(ulong) max_size);
			ut_error;
		}
	}

#ifdef BTR_CUR_HASH_ADAPT
	if (!reorg && leaf && (cursor->flag == BTR_CUR_HASH)) {
		btr_search_update_hash_node_on_insert(cursor);
	} else {
		btr_search_update_hash_on_insert(cursor);
	}
#endif

	if (!(flags & BTR_NO_LOCKING_FLAG) && inherit) {

		lock_update_insert(block, *rec);
	}

#if 0
	fprintf(stderr, "Insert into page %lu, max ins size %lu,"
		" rec %lu ind type %lu\n",
		buf_block_get_page_no(block), max_size,
		rec_size + PAGE_DIR_SLOT_SIZE, index->type);
#endif
	if (leaf && !dict_index_is_clust(index)) {
		/* Update the free bits of the B-tree page in the
		insert buffer bitmap. */

		/* The free bits in the insert buffer bitmap must
		never exceed the free space on a page.  It is safe to
		decrement or reset the bits in the bitmap in a
		mini-transaction that is committed before the
		mini-transaction that affects the free space. */

		/* It is unsafe to increment the bits in a separately
		committed mini-transaction, because in crash recovery,
		the free bits could momentarily be set too high. */

		if (zip_size) {
			/* Update the bits in the same mini-transaction. */
			ibuf_update_free_bits_zip(block, mtr);
		} else {
			/* Decrement the bits in a separate
			mini-transaction. */
			ibuf_update_free_bits_if_full(
				block, max_size,
				rec_size + PAGE_DIR_SLOT_SIZE);
		}
	}

	*big_rec = big_rec_vec;

	return(DB_SUCCESS);
}

/*************************************************************//**
Performs an insert on a page of an index tree. It is assumed that mtr
holds an x-latch on the tree and on the cursor page. If the insert is
made on the leaf level, to avoid deadlocks, mtr must also own x-latches
to brothers of page, if those brothers exist.
@return	DB_SUCCESS or error number */
UNIV_INTERN
ulint
btr_cur_pessimistic_insert(
/*=======================*/
	ulint		flags,	/*!< in: undo logging and locking flags: if not
				zero, the parameter thr should be
				specified; if no undo logging is specified,
				then the caller must have reserved enough
				free extents in the file space so that the
				insertion will certainly succeed */
	btr_cur_t*	cursor,	/*!< in: cursor after which to insert;
				cursor stays valid */
	dtuple_t*	entry,	/*!< in/out: entry to insert */
	rec_t**		rec,	/*!< out: pointer to inserted record if
				succeed */
	big_rec_t**	big_rec,/*!< out: big rec vector whose fields have to
				be stored externally by the caller, or
				NULL */
	ulint		n_ext,	/*!< in: number of externally stored columns */
	que_thr_t*	thr,	/*!< in: query thread or NULL */
	mtr_t*		mtr)	/*!< in: mtr */
{
	dict_index_t*	index		= cursor->index;
	ulint		zip_size	= dict_table_zip_size(index->table);
	big_rec_t*	big_rec_vec	= NULL;
	mem_heap_t*	heap		= NULL;
	ulint		err;
	ibool		dummy_inh;
	ibool		success;
	ulint		n_extents	= 0;
	ulint		n_reserved;

	ut_ad(dtuple_check_typed(entry));

	*big_rec = NULL;

	ut_ad(mtr_memo_contains(mtr,
				dict_index_get_lock(btr_cur_get_index(cursor)),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains(mtr, btr_cur_get_block(cursor),
				MTR_MEMO_PAGE_X_FIX));

	cursor->flag = BTR_CUR_BINARY;

	/* Check locks and write to undo log, if specified */

	err = btr_cur_ins_lock_and_undo(flags, cursor, entry,
					thr, mtr, &dummy_inh);

	if (err != DB_SUCCESS) {

		return(err);
	}

	if (!(flags & BTR_NO_UNDO_LOG_FLAG)) {
		/* First reserve enough free space for the file segments
		of the index tree, so that the insert will not fail because
		of lack of space */

		n_extents = cursor->tree_height / 16 + 3;

		success = fsp_reserve_free_extents(&n_reserved, index->space,
						   n_extents, FSP_NORMAL, mtr);
		if (!success) {
			return(DB_OUT_OF_FILE_SPACE);
		}
	}

	if (page_zip_rec_needs_ext(rec_get_converted_size(index, entry, n_ext),
				   dict_table_is_comp(index->table),
				   dict_index_get_n_fields(index),
				   zip_size)) {
		/* The record is so big that we have to store some fields
		externally on separate database pages */

		if (UNIV_LIKELY_NULL(big_rec_vec)) {
			/* This should never happen, but we handle
			the situation in a robust manner. */
			ut_ad(0);
			dtuple_convert_back_big_rec(index, entry, big_rec_vec);
		}

		big_rec_vec = dtuple_convert_big_rec(index, entry, &n_ext);

		if (big_rec_vec == NULL) {

			if (n_extents > 0) {
				fil_space_release_free_extents(index->space,
							       n_reserved);
			}
			return(DB_TOO_BIG_RECORD);
		}
	}

	if (dict_index_get_page(index)
	    == buf_block_get_page_no(btr_cur_get_block(cursor))) {

		/* The page is the root page */
		*rec = btr_root_raise_and_insert(cursor, entry, n_ext, mtr);
	} else {
		*rec = btr_page_split_and_insert(cursor, entry, n_ext, mtr);
	}

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}

	ut_ad(page_rec_get_next(btr_cur_get_rec(cursor)) == *rec);

#ifdef BTR_CUR_ADAPT
	btr_search_update_hash_on_insert(cursor);
#endif
	if (!(flags & BTR_NO_LOCKING_FLAG)) {

		lock_update_insert(btr_cur_get_block(cursor), *rec);
	}

	if (n_extents > 0) {
		fil_space_release_free_extents(index->space, n_reserved);
	}

	*big_rec = big_rec_vec;

	return(DB_SUCCESS);
}

/*==================== B-TREE UPDATE =========================*/

/*************************************************************//**
For an update, checks the locks and does the undo logging.
@return	DB_SUCCESS, DB_WAIT_LOCK, or error number */
UNIV_INLINE
ulint
btr_cur_upd_lock_and_undo(
/*======================*/
	ulint		flags,	/*!< in: undo logging and locking flags */
	btr_cur_t*	cursor,	/*!< in: cursor on record to update */
	const upd_t*	update,	/*!< in: update vector */
	ulint		cmpl_info,/*!< in: compiler info on secondary index
				updates */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr,	/*!< in/out: mini-transaction */
	roll_ptr_t*	roll_ptr)/*!< out: roll pointer */
{
	dict_index_t*	index;
	rec_t*		rec;
	ulint		err;

	ut_ad(cursor && update && thr && roll_ptr);

	rec = btr_cur_get_rec(cursor);
	index = cursor->index;

	if (!dict_index_is_clust(index)) {
		/* We do undo logging only when we update a clustered index
		record */
		return(lock_sec_rec_modify_check_and_lock(
			       flags, btr_cur_get_block(cursor), rec,
			       index, thr, mtr));
	}

	/* Check if we have to wait for a lock: enqueue an explicit lock
	request if yes */

	err = DB_SUCCESS;

	if (!(flags & BTR_NO_LOCKING_FLAG)) {
		mem_heap_t*	heap		= NULL;
		ulint		offsets_[REC_OFFS_NORMAL_SIZE];
		rec_offs_init(offsets_);

		err = lock_clust_rec_modify_check_and_lock(
			flags, btr_cur_get_block(cursor), rec, index,
			rec_get_offsets(rec, index, offsets_,
					ULINT_UNDEFINED, &heap), thr);
		if (UNIV_LIKELY_NULL(heap)) {
			mem_heap_free(heap);
		}
		if (err != DB_SUCCESS) {

			return(err);
		}
	}

	/* Append the info about the update in the undo log */

	err = trx_undo_report_row_operation(flags, TRX_UNDO_MODIFY_OP, thr,
					    index, NULL, update,
					    cmpl_info, rec, roll_ptr);
	return(err);
}

/***********************************************************//**
Writes a redo log record of updating a record in-place. */
UNIV_INLINE
void
btr_cur_update_in_place_log(
/*========================*/
	ulint		flags,		/*!< in: flags */
	rec_t*		rec,		/*!< in: record */
	dict_index_t*	index,		/*!< in: index where cursor positioned */
	const upd_t*	update,		/*!< in: update vector */
	trx_t*		trx,		/*!< in: transaction */
	roll_ptr_t	roll_ptr,	/*!< in: roll ptr */
	mtr_t*		mtr)		/*!< in: mtr */
{
	byte*	log_ptr;
	page_t*	page	= page_align(rec);
	ut_ad(flags < 256);
	ut_ad(!!page_is_comp(page) == dict_table_is_comp(index->table));

	log_ptr = mlog_open_and_write_index(mtr, rec, index, page_is_comp(page)
					    ? MLOG_COMP_REC_UPDATE_IN_PLACE
					    : MLOG_REC_UPDATE_IN_PLACE,
					    1 + DATA_ROLL_PTR_LEN + 14 + 2
					    + MLOG_BUF_MARGIN);

	if (!log_ptr) {
		/* Logging in mtr is switched off during crash recovery */
		return;
	}

	/* The code below assumes index is a clustered index: change index to
	the clustered index if we are updating a secondary index record (or we
	could as well skip writing the sys col values to the log in this case
	because they are not needed for a secondary index record update) */

	index = dict_table_get_first_index(index->table);

	mach_write_to_1(log_ptr, flags);
	log_ptr++;

	log_ptr = row_upd_write_sys_vals_to_log(index, trx, roll_ptr, log_ptr,
						mtr);
	mach_write_to_2(log_ptr, page_offset(rec));
	log_ptr += 2;

	row_upd_index_write_log(update, log_ptr, mtr);
}
#endif /* UNIV_HOTBACKUP */

/***********************************************************//**
Parses a redo log record of updating a record in-place.
@return	end of log record or NULL */
UNIV_INTERN
byte*
btr_cur_parse_update_in_place(
/*==========================*/
	byte*		ptr,	/*!< in: buffer */
	byte*		end_ptr,/*!< in: buffer end */
	page_t*		page,	/*!< in/out: page or NULL */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page, or NULL */
	dict_index_t*	index)	/*!< in: index corresponding to page */
{
	ulint		flags;
	rec_t*		rec;
	upd_t*		update;
	ulint		pos;
	trx_id_t	trx_id;
	roll_ptr_t	roll_ptr;
	ulint		rec_offset;
	mem_heap_t*	heap;
	ulint*		offsets;

	if (end_ptr < ptr + 1) {

		return(NULL);
	}

	flags = mach_read_from_1(ptr);
	ptr++;

	ptr = row_upd_parse_sys_vals(ptr, end_ptr, &pos, &trx_id, &roll_ptr);

	if (ptr == NULL) {

		return(NULL);
	}

	if (end_ptr < ptr + 2) {

		return(NULL);
	}

	rec_offset = mach_read_from_2(ptr);
	ptr += 2;

	ut_a(rec_offset <= UNIV_PAGE_SIZE);

	heap = mem_heap_create(256);

	ptr = row_upd_index_parse(ptr, end_ptr, heap, &update);

	if (!ptr || !page) {

		goto func_exit;
	}

	ut_a((ibool)!!page_is_comp(page) == dict_table_is_comp(index->table));
	rec = page + rec_offset;

	/* We do not need to reserve btr_search_latch, as the page is only
	being recovered, and there cannot be a hash index to it. */

	offsets = rec_get_offsets(rec, index, NULL, ULINT_UNDEFINED, &heap);

	if (!(flags & BTR_KEEP_SYS_FLAG)) {
		row_upd_rec_sys_fields_in_recovery(rec, page_zip, offsets,
						   pos, trx_id, roll_ptr);
	}

	row_upd_rec_in_place(rec, index, offsets, update, page_zip);

func_exit:
	mem_heap_free(heap);

	return(ptr);
}

#ifndef UNIV_HOTBACKUP
/*************************************************************//**
See if there is enough place in the page modification log to log
an update-in-place.
@return	TRUE if enough place */
UNIV_INTERN
ibool
btr_cur_update_alloc_zip(
/*=====================*/
	page_zip_des_t*	page_zip,/*!< in/out: compressed page */
	buf_block_t*	block,	/*!< in/out: buffer page */
	dict_index_t*	index,	/*!< in: the index corresponding to the block */
	ulint		length,	/*!< in: size needed */
	ibool		create,	/*!< in: TRUE=delete-and-insert,
				FALSE=update-in-place */
	mtr_t*		mtr)	/*!< in: mini-transaction */
{
	ut_a(page_zip == buf_block_get_page_zip(block));
	ut_ad(page_zip);
	ut_ad(!dict_index_is_ibuf(index));

	if (page_zip_available(page_zip, dict_index_is_clust(index),
			       length, create)) {
		return(TRUE);
	}

	if (!page_zip->m_nonempty) {
		/* The page has been freshly compressed, so
		recompressing it will not help. */
		return(FALSE);
	}

	if (!page_zip_compress(page_zip, buf_block_get_frame(block),
			       index, mtr)) {
		/* Unable to compress the page */
		return(FALSE);
	}

	/* After recompressing a page, we must make sure that the free
	bits in the insert buffer bitmap will not exceed the free
	space on the page.  Because this function will not attempt
	recompression unless page_zip_available() fails above, it is
	safe to reset the free bits if page_zip_available() fails
	again, below.  The free bits can safely be reset in a separate
	mini-transaction.  If page_zip_available() succeeds below, we
	can be sure that the page_zip_compress() above did not reduce
	the free space available on the page. */

	if (!page_zip_available(page_zip, dict_index_is_clust(index),
				length, create)) {
		/* Out of space: reset the free bits. */
		if (!dict_index_is_clust(index)
		    && page_is_leaf(buf_block_get_frame(block))) {
			ibuf_reset_free_bits(block);
		}
		return(FALSE);
	}

	return(TRUE);
}

/*************************************************************//**
Updates a record when the update causes no size changes in its fields.
We assume here that the ordering fields of the record do not change.
@return	DB_SUCCESS or error number */
UNIV_INTERN
ulint
btr_cur_update_in_place(
/*====================*/
	ulint		flags,	/*!< in: undo logging and locking flags */
	btr_cur_t*	cursor,	/*!< in: cursor on the record to update;
				cursor stays valid and positioned on the
				same record */
	const upd_t*	update,	/*!< in: update vector */
	ulint		cmpl_info,/*!< in: compiler info on secondary index
				updates */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr)	/*!< in: mtr; must be committed before
				latching any further pages */
{
	dict_index_t*	index;
	buf_block_t*	block;
	page_zip_des_t*	page_zip;
	ulint		err;
	rec_t*		rec;
	roll_ptr_t	roll_ptr	= 0;
	trx_t*		trx;
	ulint		was_delete_marked;
	ibool		is_hashed;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	rec_offs_init(offsets_);

	rec = btr_cur_get_rec(cursor);
	index = cursor->index;
	ut_ad(!!page_rec_is_comp(rec) == dict_table_is_comp(index->table));
	/* The insert buffer tree should never be updated in place. */
	ut_ad(!dict_index_is_ibuf(index));

	trx = thr_get_trx(thr);
	offsets = rec_get_offsets(rec, index, offsets, ULINT_UNDEFINED, &heap);
#ifdef UNIV_DEBUG
	if (btr_cur_print_record_ops && thr) {
		btr_cur_trx_report(trx, index, "update ");
		rec_print_new(stderr, rec, offsets);
	}
#endif /* UNIV_DEBUG */

	block = btr_cur_get_block(cursor);
	page_zip = buf_block_get_page_zip(block);

	/* Check that enough space is available on the compressed page. */
	if (page_zip
	    && !btr_cur_update_alloc_zip(page_zip, block, index,
					 rec_offs_size(offsets), FALSE, mtr)) {
		return(DB_ZIP_OVERFLOW);
	}

	/* Do lock checking and undo logging */
	err = btr_cur_upd_lock_and_undo(flags, cursor, update, cmpl_info,
					thr, mtr, &roll_ptr);
	if (UNIV_UNLIKELY(err != DB_SUCCESS)) {

		if (UNIV_LIKELY_NULL(heap)) {
			mem_heap_free(heap);
		}
		return(err);
	}

	if (!(flags & BTR_KEEP_SYS_FLAG)) {
		row_upd_rec_sys_fields(rec, NULL,
				       index, offsets, trx, roll_ptr);
	}

	was_delete_marked = rec_get_deleted_flag(
		rec, page_is_comp(buf_block_get_frame(block)));

	is_hashed = (block->index != NULL);

	if (is_hashed) {
		/* TO DO: Can we skip this if none of the fields
		index->search_info->curr_n_fields
		are being updated? */

		/* The function row_upd_changes_ord_field_binary works only
		if the update vector was built for a clustered index, we must
		NOT call it if index is secondary */

		if (!dict_index_is_clust(index)
		    || row_upd_changes_ord_field_binary(index, update, thr,
							NULL, NULL)) {

			/* Remove possible hash index pointer to this record */
			btr_search_update_hash_on_delete(cursor);
		}

		rw_lock_x_lock(&btr_search_latch);
	}

	row_upd_rec_in_place(rec, index, offsets, update, page_zip);

	if (is_hashed) {
		rw_lock_x_unlock(&btr_search_latch);
	}

	if (page_zip && !dict_index_is_clust(index)
	    && page_is_leaf(buf_block_get_frame(block))) {
		/* Update the free bits in the insert buffer. */
		ibuf_update_free_bits_zip(block, mtr);
	}

	btr_cur_update_in_place_log(flags, rec, index, update,
				    trx, roll_ptr, mtr);

	if (was_delete_marked
	    && !rec_get_deleted_flag(rec, page_is_comp(
					     buf_block_get_frame(block)))) {
		/* The new updated record owns its possible externally
		stored fields */

		btr_cur_unmark_extern_fields(page_zip,
					     rec, index, offsets, mtr);
	}

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}
	return(DB_SUCCESS);
}

/*************************************************************//**
Tries to update a record on a page in an index tree. It is assumed that mtr
holds an x-latch on the page. The operation does not succeed if there is too
little space on the page or if the update would result in too empty a page,
so that tree compression is recommended. We assume here that the ordering
fields of the record do not change.
@return DB_SUCCESS, or DB_OVERFLOW if the updated record does not fit,
DB_UNDERFLOW if the page would become too empty, or DB_ZIP_OVERFLOW if
there is not enough space left on the compressed page */
UNIV_INTERN
ulint
btr_cur_optimistic_update(
/*======================*/
	ulint		flags,	/*!< in: undo logging and locking flags */
	btr_cur_t*	cursor,	/*!< in: cursor on the record to update;
				cursor stays valid and positioned on the
				same record */
	const upd_t*	update,	/*!< in: update vector; this must also
				contain trx id and roll ptr fields */
	ulint		cmpl_info,/*!< in: compiler info on secondary index
				updates */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr)	/*!< in: mtr; must be committed before
				latching any further pages */
{
	dict_index_t*	index;
	page_cur_t*	page_cursor;
	ulint		err;
	buf_block_t*	block;
	page_t*		page;
	page_zip_des_t*	page_zip;
	rec_t*		rec;
	ulint		max_size;
	ulint		new_rec_size;
	ulint		old_rec_size;
	dtuple_t*	new_entry;
	roll_ptr_t	roll_ptr;
	trx_t*		trx;
	mem_heap_t*	heap;
	ulint		i;
	ulint		n_ext;
	ulint*		offsets;

	block = btr_cur_get_block(cursor);
	page = buf_block_get_frame(block);
	rec = btr_cur_get_rec(cursor);
	index = cursor->index;
	ut_ad(!!page_rec_is_comp(rec) == dict_table_is_comp(index->table));
	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	/* The insert buffer tree should never be updated in place. */
	ut_ad(!dict_index_is_ibuf(index));

	heap = mem_heap_create(1024);
	offsets = rec_get_offsets(rec, index, NULL, ULINT_UNDEFINED, &heap);
#ifdef UNIV_BLOB_NULL_DEBUG
	ut_a(!rec_offs_any_null_extern(rec, offsets));
#endif /* UNIV_BLOB_NULL_DEBUG */

#ifdef UNIV_DEBUG
	if (btr_cur_print_record_ops && thr) {
		btr_cur_trx_report(thr_get_trx(thr), index, "update ");
		rec_print_new(stderr, rec, offsets);
	}
#endif /* UNIV_DEBUG */

	if (!row_upd_changes_field_size_or_external(index, offsets, update)) {

		/* The simplest and the most common case: the update does not
		change the size of any field and none of the updated fields is
		externally stored in rec or update, and there is enough space
		on the compressed page to log the update. */

		mem_heap_free(heap);
		return(btr_cur_update_in_place(flags, cursor, update,
					       cmpl_info, thr, mtr));
	}

	if (rec_offs_any_extern(offsets)) {
any_extern:
		/* Externally stored fields are treated in pessimistic
		update */

		mem_heap_free(heap);
		return(DB_OVERFLOW);
	}

	for (i = 0; i < upd_get_n_fields(update); i++) {
		if (dfield_is_ext(&upd_get_nth_field(update, i)->new_val)) {

			goto any_extern;
		}
	}

	page_cursor = btr_cur_get_page_cur(cursor);

	new_entry = row_rec_to_index_entry(ROW_COPY_DATA, rec, index, offsets,
					   &n_ext, heap);
	/* We checked above that there are no externally stored fields. */
	ut_a(!n_ext);

	/* The page containing the clustered index record
	corresponding to new_entry is latched in mtr.
	Thus the following call is safe. */
	row_upd_index_replace_new_col_vals_index_pos(new_entry, index, update,
						     FALSE, heap);
	old_rec_size = rec_offs_size(offsets);
	new_rec_size = rec_get_converted_size(index, new_entry, 0);

	page_zip = buf_block_get_page_zip(block);
#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */

	if (page_zip
	    && !btr_cur_update_alloc_zip(page_zip, block, index,
					 new_rec_size, TRUE, mtr)) {
		err = DB_ZIP_OVERFLOW;
		goto err_exit;
	}

	if (UNIV_UNLIKELY(new_rec_size
			  >= (page_get_free_space_of_empty(page_is_comp(page))
			      / 2))) {

		err = DB_OVERFLOW;
		goto err_exit;
	}

	if (UNIV_UNLIKELY(page_get_data_size(page)
			  - old_rec_size + new_rec_size
			  < BTR_CUR_PAGE_COMPRESS_LIMIT)) {

		/* The page would become too empty */

		err = DB_UNDERFLOW;
		goto err_exit;
	}

	/* We do not attempt to reorganize if the page is compressed.
	This is because the page may fail to compress after reorganization. */
	max_size = page_zip
		? page_get_max_insert_size(page, 1)
		: (old_rec_size
		   + page_get_max_insert_size_after_reorganize(page, 1));

	if (!(((max_size >= BTR_CUR_PAGE_REORGANIZE_LIMIT)
	       && (max_size >= new_rec_size))
	      || (page_get_n_recs(page) <= 1))) {

		/* There was not enough space, or it did not pay to
		reorganize: for simplicity, we decide what to do assuming a
		reorganization is needed, though it might not be necessary */

		err = DB_OVERFLOW;
		goto err_exit;
	}

	/* Do lock checking and undo logging */
	err = btr_cur_upd_lock_and_undo(flags, cursor, update, cmpl_info,
					thr, mtr, &roll_ptr);
	if (err != DB_SUCCESS) {

		goto err_exit;
	}

	/* Ok, we may do the replacement. Store on the page infimum the
	explicit locks on rec, before deleting rec (see the comment in
	btr_cur_pessimistic_update). */

	lock_rec_store_on_page_infimum(block, rec);

	btr_search_update_hash_on_delete(cursor);

	/* The call to row_rec_to_index_entry(ROW_COPY_DATA, ...) above
	invokes rec_offs_make_valid() to point to the copied record that
	the fields of new_entry point to.  We have to undo it here. */
	ut_ad(rec_offs_validate(NULL, index, offsets));
	rec_offs_make_valid(page_cur_get_rec(page_cursor), index, offsets);

	page_cur_delete_rec(page_cursor, index, offsets, mtr);

	page_cur_move_to_prev(page_cursor);

	trx = thr_get_trx(thr);

	if (!(flags & BTR_KEEP_SYS_FLAG)) {
		row_upd_index_entry_sys_field(new_entry, index, DATA_ROLL_PTR,
					      roll_ptr);
		row_upd_index_entry_sys_field(new_entry, index, DATA_TRX_ID,
					      trx->id);
	}

	/* There are no externally stored columns in new_entry */
	rec = btr_cur_insert_if_possible(cursor, new_entry, 0/*n_ext*/, mtr);
	ut_a(rec); /* <- We calculated above the insert would fit */

	if (page_zip && !dict_index_is_clust(index)
	    && page_is_leaf(page)) {
		/* Update the free bits in the insert buffer. */
		ibuf_update_free_bits_zip(block, mtr);
	}

	/* Restore the old explicit lock state on the record */

	lock_rec_restore_from_page_infimum(block, rec, block);

	page_cur_move_to_next(page_cursor);

	err = DB_SUCCESS;
err_exit:
	mem_heap_free(heap);
	return(err);
}

/*************************************************************//**
If, in a split, a new supremum record was created as the predecessor of the
updated record, the supremum record must inherit exactly the locks on the
updated record. In the split it may have inherited locks from the successor
of the updated record, which is not correct. This function restores the
right locks for the new supremum. */
static
void
btr_cur_pess_upd_restore_supremum(
/*==============================*/
	buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*	rec,	/*!< in: updated record */
	mtr_t*		mtr)	/*!< in: mtr */
{
	page_t*		page;
	buf_block_t*	prev_block;
	ulint		space;
	ulint		zip_size;
	ulint		prev_page_no;

	page = buf_block_get_frame(block);

	if (page_rec_get_next(page_get_infimum_rec(page)) != rec) {
		/* Updated record is not the first user record on its page */

		return;
	}

	space = buf_block_get_space(block);
	zip_size = buf_block_get_zip_size(block);
	prev_page_no = btr_page_get_prev(page, mtr);

	ut_ad(prev_page_no != FIL_NULL);
	prev_block = buf_page_get_with_no_latch(space, zip_size,
						prev_page_no, mtr);
#ifdef UNIV_BTR_DEBUG
	ut_a(btr_page_get_next(prev_block->frame, mtr)
	     == page_get_page_no(page));
#endif /* UNIV_BTR_DEBUG */

	/* We must already have an x-latch on prev_block! */
	ut_ad(mtr_memo_contains(mtr, prev_block, MTR_MEMO_PAGE_X_FIX));

	lock_rec_reset_and_inherit_gap_locks(prev_block, block,
					     PAGE_HEAP_NO_SUPREMUM,
					     page_rec_get_heap_no(rec));
}

/*************************************************************//**
Performs an update of a record on a page of a tree. It is assumed
that mtr holds an x-latch on the tree and on the cursor page. If the
update is made on the leaf level, to avoid deadlocks, mtr must also
own x-latches to brothers of page, if those brothers exist. We assume
here that the ordering fields of the record do not change.
@return	DB_SUCCESS or error code */
UNIV_INTERN
ulint
btr_cur_pessimistic_update(
/*=======================*/
	ulint		flags,	/*!< in: undo logging, locking, and rollback
				flags */
	btr_cur_t*	cursor,	/*!< in/out: cursor on the record to update;
				cursor may become invalid if *big_rec == NULL
				|| !(flags & BTR_KEEP_POS_FLAG) */
	mem_heap_t**	heap,	/*!< in/out: pointer to memory heap, or NULL */
	big_rec_t**	big_rec,/*!< out: big rec vector whose fields have to
				be stored externally by the caller, or NULL */
	const upd_t*	update,	/*!< in: update vector; this is allowed also
				contain trx id and roll ptr fields, but
				the values in update vector have no effect */
	ulint		cmpl_info,/*!< in: compiler info on secondary index
				updates */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr)	/*!< in: mtr; must be committed before
				latching any further pages */
{
	big_rec_t*	big_rec_vec	= NULL;
	big_rec_t*	dummy_big_rec;
	dict_index_t*	index;
	buf_block_t*	block;
	page_t*		page;
	page_zip_des_t*	page_zip;
	rec_t*		rec;
	page_cur_t*	page_cursor;
	dtuple_t*	new_entry;
	ulint		err;
	ulint		optim_err;
	roll_ptr_t	roll_ptr;
	trx_t*		trx;
	ibool		was_first;
	ulint		n_extents	= 0;
	ulint		n_reserved;
	ulint		n_ext;
	ulint*		offsets		= NULL;

	*big_rec = NULL;

	block = btr_cur_get_block(cursor);
	page = buf_block_get_frame(block);
	page_zip = buf_block_get_page_zip(block);
	rec = btr_cur_get_rec(cursor);
	index = cursor->index;

	ut_ad(mtr_memo_contains(mtr, dict_index_get_lock(index),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */
	/* The insert buffer tree should never be updated in place. */
	ut_ad(!dict_index_is_ibuf(index));

	optim_err = btr_cur_optimistic_update(flags, cursor, update,
					      cmpl_info, thr, mtr);

	switch (optim_err) {
	case DB_UNDERFLOW:
	case DB_OVERFLOW:
	case DB_ZIP_OVERFLOW:
		break;
	default:
		return(optim_err);
	}

	/* Do lock checking and undo logging */
	err = btr_cur_upd_lock_and_undo(flags, cursor, update, cmpl_info,
					thr, mtr, &roll_ptr);
	if (err != DB_SUCCESS) {

		return(err);
	}

	if (optim_err == DB_OVERFLOW) {
		ulint	reserve_flag;

		/* First reserve enough free space for the file segments
		of the index tree, so that the update will not fail because
		of lack of space */

		n_extents = cursor->tree_height / 16 + 3;

		if (flags & BTR_NO_UNDO_LOG_FLAG) {
			reserve_flag = FSP_CLEANING;
		} else {
			reserve_flag = FSP_NORMAL;
		}

		if (!fsp_reserve_free_extents(&n_reserved, index->space,
					      n_extents, reserve_flag, mtr)) {
			return(DB_OUT_OF_FILE_SPACE);
		}
	}

	if (!*heap) {
		*heap = mem_heap_create(1024);
	}
	offsets = rec_get_offsets(rec, index, NULL, ULINT_UNDEFINED, heap);

	trx = thr_get_trx(thr);

	new_entry = row_rec_to_index_entry(ROW_COPY_DATA, rec, index, offsets,
					   &n_ext, *heap);
	/* The call to row_rec_to_index_entry(ROW_COPY_DATA, ...) above
	invokes rec_offs_make_valid() to point to the copied record that
	the fields of new_entry point to.  We have to undo it here. */
	ut_ad(rec_offs_validate(NULL, index, offsets));
	rec_offs_make_valid(rec, index, offsets);

	/* The page containing the clustered index record
	corresponding to new_entry is latched in mtr.  If the
	clustered index record is delete-marked, then its externally
	stored fields cannot have been purged yet, because then the
	purge would also have removed the clustered index record
	itself.  Thus the following call is safe. */
	row_upd_index_replace_new_col_vals_index_pos(new_entry, index, update,
						     FALSE, *heap);
	if (!(flags & BTR_KEEP_SYS_FLAG)) {
		row_upd_index_entry_sys_field(new_entry, index, DATA_ROLL_PTR,
					      roll_ptr);
		row_upd_index_entry_sys_field(new_entry, index, DATA_TRX_ID,
					      trx->id);
	}

	if ((flags & BTR_NO_UNDO_LOG_FLAG) && rec_offs_any_extern(offsets)) {
		/* We are in a transaction rollback undoing a row
		update: we must free possible externally stored fields
		which got new values in the update, if they are not
		inherited values. They can be inherited if we have
		updated the primary key to another value, and then
		update it back again. */

		ut_ad(big_rec_vec == NULL);

		btr_rec_free_updated_extern_fields(
			index, rec, page_zip, offsets, update,
			trx_is_recv(trx) ? RB_RECOVERY : RB_NORMAL, mtr);
	}

	/* We have to set appropriate extern storage bits in the new
	record to be inserted: we have to remember which fields were such */

	ut_ad(!page_is_comp(page) || !rec_get_node_ptr_flag(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));
	n_ext += btr_push_update_extern_fields(new_entry, update, *heap);

	if (page_zip) {
		ut_ad(page_is_comp(page));
		if (page_zip_rec_needs_ext(
			    rec_get_converted_size(index, new_entry, n_ext),
			    TRUE,
			    dict_index_get_n_fields(index),
			    page_zip_get_size(page_zip))) {

			goto make_external;
		}
	} else if (page_zip_rec_needs_ext(
			   rec_get_converted_size(index, new_entry, n_ext),
			   page_is_comp(page), 0, 0)) {
make_external:
		big_rec_vec = dtuple_convert_big_rec(index, new_entry, &n_ext);
		if (UNIV_UNLIKELY(big_rec_vec == NULL)) {

			err = DB_TOO_BIG_RECORD;
			goto return_after_reservations;
		}

		ut_ad(page_is_leaf(page));
		ut_ad(dict_index_is_clust(index));
		ut_ad(flags & BTR_KEEP_POS_FLAG);
	}

	/* Store state of explicit locks on rec on the page infimum record,
	before deleting rec. The page infimum acts as a dummy carrier of the
	locks, taking care also of lock releases, before we can move the locks
	back on the actual record. There is a special case: if we are
	inserting on the root page and the insert causes a call of
	btr_root_raise_and_insert. Therefore we cannot in the lock system
	delete the lock structs set on the root page even if the root
	page carries just node pointers. */

	lock_rec_store_on_page_infimum(block, rec);

	btr_search_update_hash_on_delete(cursor);

#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */
	page_cursor = btr_cur_get_page_cur(cursor);

	page_cur_delete_rec(page_cursor, index, offsets, mtr);

	page_cur_move_to_prev(page_cursor);

	rec = btr_cur_insert_if_possible(cursor, new_entry, n_ext, mtr);

	if (rec) {
		page_cursor->rec = rec;

		lock_rec_restore_from_page_infimum(btr_cur_get_block(cursor),
						   rec, block);

		offsets = rec_get_offsets(rec, index, offsets,
					  ULINT_UNDEFINED, heap);

		if (!rec_get_deleted_flag(rec, rec_offs_comp(offsets))) {
			/* The new inserted record owns its possible externally
			stored fields */
			btr_cur_unmark_extern_fields(page_zip,
						     rec, index, offsets, mtr);
		}

		btr_cur_compress_if_useful(
			cursor,
			big_rec_vec != NULL && (flags & BTR_KEEP_POS_FLAG),
			mtr);

		if (page_zip && !dict_index_is_clust(index)
		    && page_is_leaf(page)) {
			/* Update the free bits in the insert buffer. */
			ibuf_update_free_bits_zip(block, mtr);
		}

		err = DB_SUCCESS;
		goto return_after_reservations;
	} else {
		/* If the page is compressed and it initially
		compresses very well, and there is a subsequent insert
		of a badly-compressing record, it is possible for
		btr_cur_optimistic_update() to return DB_UNDERFLOW and
		btr_cur_insert_if_possible() to return FALSE. */
		ut_a(page_zip || optim_err != DB_UNDERFLOW);

		/* Out of space: reset the free bits. */
		if (!dict_index_is_clust(index)
		    && page_is_leaf(page)) {
			ibuf_reset_free_bits(block);
		}
	}

	if (big_rec_vec) {
		ut_ad(page_is_leaf(page));
		ut_ad(dict_index_is_clust(index));
		ut_ad(flags & BTR_KEEP_POS_FLAG);

		/* btr_page_split_and_insert() in
		btr_cur_pessimistic_insert() invokes
		mtr_memo_release(mtr, index->lock, MTR_MEMO_X_LOCK).
		We must keep the index->lock when we created a
		big_rec, so that row_upd_clust_rec() can store the
		big_rec in the same mini-transaction. */

		mtr_x_lock(dict_index_get_lock(index), mtr);
	}

	/* Was the record to be updated positioned as the first user
	record on its page? */
	was_first = page_cur_is_before_first(page_cursor);

	/* Lock checks and undo logging were already performed by
	btr_cur_upd_lock_and_undo(). We do not try
	btr_cur_optimistic_insert() because
	btr_cur_insert_if_possible() already failed above. */

	err = btr_cur_pessimistic_insert(BTR_NO_UNDO_LOG_FLAG
					 | BTR_NO_LOCKING_FLAG
					 | BTR_KEEP_SYS_FLAG,
					 cursor, new_entry, &rec,
					 &dummy_big_rec, n_ext, NULL, mtr);
	ut_a(rec);
	ut_a(err == DB_SUCCESS);
	ut_a(dummy_big_rec == NULL);
	page_cursor->rec = rec;

	if (dict_index_is_sec_or_ibuf(index)) {
		/* Update PAGE_MAX_TRX_ID in the index page header.
		It was not updated by btr_cur_pessimistic_insert()
		because of BTR_NO_LOCKING_FLAG. */
		buf_block_t*	rec_block;

		rec_block = btr_cur_get_block(cursor);

		page_update_max_trx_id(rec_block,
				       buf_block_get_page_zip(rec_block),
				       trx->id, mtr);
	}

	if (!rec_get_deleted_flag(rec, rec_offs_comp(offsets))) {
		/* The new inserted record owns its possible externally
		stored fields */
		buf_block_t*	rec_block = btr_cur_get_block(cursor);

#ifdef UNIV_ZIP_DEBUG
		ut_a(!page_zip || page_zip_validate(page_zip, page, index));
		page = buf_block_get_frame(rec_block);
#endif /* UNIV_ZIP_DEBUG */
		page_zip = buf_block_get_page_zip(rec_block);

		offsets = rec_get_offsets(rec, index, offsets,
					  ULINT_UNDEFINED, heap);
		btr_cur_unmark_extern_fields(page_zip,
					     rec, index, offsets, mtr);
	}

	lock_rec_restore_from_page_infimum(btr_cur_get_block(cursor),
					   rec, block);

	/* If necessary, restore also the correct lock state for a new,
	preceding supremum record created in a page split. While the old
	record was nonexistent, the supremum might have inherited its locks
	from a wrong record. */

	if (!was_first) {
		btr_cur_pess_upd_restore_supremum(btr_cur_get_block(cursor),
						  rec, mtr);
	}

return_after_reservations:
#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */

	if (n_extents > 0) {
		fil_space_release_free_extents(index->space, n_reserved);
	}

	*big_rec = big_rec_vec;

	return(err);
}

/*==================== B-TREE DELETE MARK AND UNMARK ===============*/

/****************************************************************//**
Writes the redo log record for delete marking or unmarking of an index
record. */
UNIV_INLINE
void
btr_cur_del_mark_set_clust_rec_log(
/*===============================*/
	ulint		flags,	/*!< in: flags */
	rec_t*		rec,	/*!< in: record */
	dict_index_t*	index,	/*!< in: index of the record */
	ibool		val,	/*!< in: value to set */
	trx_t*		trx,	/*!< in: deleting transaction */
	roll_ptr_t	roll_ptr,/*!< in: roll ptr to the undo log record */
	mtr_t*		mtr)	/*!< in: mtr */
{
	byte*	log_ptr;
	ut_ad(flags < 256);
	ut_ad(val <= 1);

	ut_ad(!!page_rec_is_comp(rec) == dict_table_is_comp(index->table));

	log_ptr = mlog_open_and_write_index(mtr, rec, index,
					    page_rec_is_comp(rec)
					    ? MLOG_COMP_REC_CLUST_DELETE_MARK
					    : MLOG_REC_CLUST_DELETE_MARK,
					    1 + 1 + DATA_ROLL_PTR_LEN
					    + 14 + 2);

	if (!log_ptr) {
		/* Logging in mtr is switched off during crash recovery */
		return;
	}

	mach_write_to_1(log_ptr, flags);
	log_ptr++;
	mach_write_to_1(log_ptr, val);
	log_ptr++;

	log_ptr = row_upd_write_sys_vals_to_log(index, trx, roll_ptr, log_ptr,
						mtr);
	mach_write_to_2(log_ptr, page_offset(rec));
	log_ptr += 2;

	mlog_close(mtr, log_ptr);
}
#endif /* !UNIV_HOTBACKUP */

/****************************************************************//**
Parses the redo log record for delete marking or unmarking of a clustered
index record.
@return	end of log record or NULL */
UNIV_INTERN
byte*
btr_cur_parse_del_mark_set_clust_rec(
/*=================================*/
	byte*		ptr,	/*!< in: buffer */
	byte*		end_ptr,/*!< in: buffer end */
	page_t*		page,	/*!< in/out: page or NULL */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page, or NULL */
	dict_index_t*	index)	/*!< in: index corresponding to page */
{
	ulint		flags;
	ulint		val;
	ulint		pos;
	trx_id_t	trx_id;
	roll_ptr_t	roll_ptr;
	ulint		offset;
	rec_t*		rec;

	ut_ad(!page
	      || !!page_is_comp(page) == dict_table_is_comp(index->table));

	if (end_ptr < ptr + 2) {

		return(NULL);
	}

	flags = mach_read_from_1(ptr);
	ptr++;
	val = mach_read_from_1(ptr);
	ptr++;

	ptr = row_upd_parse_sys_vals(ptr, end_ptr, &pos, &trx_id, &roll_ptr);

	if (ptr == NULL) {

		return(NULL);
	}

	if (end_ptr < ptr + 2) {

		return(NULL);
	}

	offset = mach_read_from_2(ptr);
	ptr += 2;

	ut_a(offset <= UNIV_PAGE_SIZE);

	if (page) {
		rec = page + offset;

		/* We do not need to reserve btr_search_latch, as the page
		is only being recovered, and there cannot be a hash index to
		it. Besides, these fields are being updated in place
		and the adaptive hash index does not depend on them. */

		btr_rec_set_deleted_flag(rec, page_zip, val);

		if (!(flags & BTR_KEEP_SYS_FLAG)) {
			mem_heap_t*	heap		= NULL;
			ulint		offsets_[REC_OFFS_NORMAL_SIZE];
			rec_offs_init(offsets_);

			row_upd_rec_sys_fields_in_recovery(
				rec, page_zip,
				rec_get_offsets(rec, index, offsets_,
						ULINT_UNDEFINED, &heap),
				pos, trx_id, roll_ptr);
			if (UNIV_LIKELY_NULL(heap)) {
				mem_heap_free(heap);
			}
		}
	}

	return(ptr);
}

#ifndef UNIV_HOTBACKUP
/***********************************************************//**
Marks a clustered index record deleted. Writes an undo log record to
undo log on this delete marking. Writes in the trx id field the id
of the deleting transaction, and in the roll ptr field pointer to the
undo log record created.
@return	DB_SUCCESS, DB_LOCK_WAIT, or error number */
UNIV_INTERN
ulint
btr_cur_del_mark_set_clust_rec(
/*===========================*/
	ulint		flags,	/*!< in: undo logging and locking flags */
	buf_block_t*	block,	/*!< in/out: buffer block of the record */
	rec_t*		rec,	/*!< in/out: record */
	dict_index_t*	index,	/*!< in: clustered index of the record */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec) */
	ibool		val,	/*!< in: value to set */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr)	/*!< in: mtr */
{
	roll_ptr_t	roll_ptr;
	ulint		err;
	page_zip_des_t*	page_zip;
	trx_t*		trx;

	ut_ad(dict_index_is_clust(index));
	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(!!page_rec_is_comp(rec) == dict_table_is_comp(index->table));
	ut_ad(buf_block_get_frame(block) == page_align(rec));
	ut_ad(page_is_leaf(page_align(rec)));

#ifdef UNIV_DEBUG
	if (btr_cur_print_record_ops && thr) {
		btr_cur_trx_report(thr_get_trx(thr), index, "del mark ");
		rec_print_new(stderr, rec, offsets);
	}
#endif /* UNIV_DEBUG */

	ut_ad(dict_index_is_clust(index));
	ut_ad(!rec_get_deleted_flag(rec, rec_offs_comp(offsets)));

	err = lock_clust_rec_modify_check_and_lock(flags, block,
						   rec, index, offsets, thr);

	if (err != DB_SUCCESS) {

		return(err);
	}

	err = trx_undo_report_row_operation(flags, TRX_UNDO_MODIFY_OP, thr,
					    index, NULL, NULL, 0, rec,
					    &roll_ptr);
	if (err != DB_SUCCESS) {

		return(err);
	}

	/* The btr_search_latch is not needed here, because
	the adaptive hash index does not depend on the delete-mark
	and the delete-mark is being updated in place. */

	page_zip = buf_block_get_page_zip(block);

	btr_blob_dbg_set_deleted_flag(rec, index, offsets, val);
	btr_rec_set_deleted_flag(rec, page_zip, val);

	trx = thr_get_trx(thr);

	if (!(flags & BTR_KEEP_SYS_FLAG)) {
		row_upd_rec_sys_fields(rec, page_zip,
				       index, offsets, trx, roll_ptr);
	}

	btr_cur_del_mark_set_clust_rec_log(flags, rec, index, val, trx,
					   roll_ptr, mtr);

	return(err);
}

/****************************************************************//**
Writes the redo log record for a delete mark setting of a secondary
index record. */
UNIV_INLINE
void
btr_cur_del_mark_set_sec_rec_log(
/*=============================*/
	rec_t*		rec,	/*!< in: record */
	ibool		val,	/*!< in: value to set */
	mtr_t*		mtr)	/*!< in: mtr */
{
	byte*	log_ptr;
	ut_ad(val <= 1);

	log_ptr = mlog_open(mtr, 11 + 1 + 2);

	if (!log_ptr) {
		/* Logging in mtr is switched off during crash recovery:
		in that case mlog_open returns NULL */
		return;
	}

	log_ptr = mlog_write_initial_log_record_fast(
		rec, MLOG_REC_SEC_DELETE_MARK, log_ptr, mtr);
	mach_write_to_1(log_ptr, val);
	log_ptr++;

	mach_write_to_2(log_ptr, page_offset(rec));
	log_ptr += 2;

	mlog_close(mtr, log_ptr);
}
#endif /* !UNIV_HOTBACKUP */

/****************************************************************//**
Parses the redo log record for delete marking or unmarking of a secondary
index record.
@return	end of log record or NULL */
UNIV_INTERN
byte*
btr_cur_parse_del_mark_set_sec_rec(
/*===============================*/
	byte*		ptr,	/*!< in: buffer */
	byte*		end_ptr,/*!< in: buffer end */
	page_t*		page,	/*!< in/out: page or NULL */
	page_zip_des_t*	page_zip)/*!< in/out: compressed page, or NULL */
{
	ulint	val;
	ulint	offset;
	rec_t*	rec;

	if (end_ptr < ptr + 3) {

		return(NULL);
	}

	val = mach_read_from_1(ptr);
	ptr++;

	offset = mach_read_from_2(ptr);
	ptr += 2;

	ut_a(offset <= UNIV_PAGE_SIZE);

	if (page) {
		rec = page + offset;

		/* We do not need to reserve btr_search_latch, as the page
		is only being recovered, and there cannot be a hash index to
		it. Besides, the delete-mark flag is being updated in place
		and the adaptive hash index does not depend on it. */

		btr_rec_set_deleted_flag(rec, page_zip, val);
	}

	return(ptr);
}

#ifndef UNIV_HOTBACKUP
/***********************************************************//**
Sets a secondary index record delete mark to TRUE or FALSE.
@return	DB_SUCCESS, DB_LOCK_WAIT, or error number */
UNIV_INTERN
ulint
btr_cur_del_mark_set_sec_rec(
/*=========================*/
	ulint		flags,	/*!< in: locking flag */
	btr_cur_t*	cursor,	/*!< in: cursor */
	ibool		val,	/*!< in: value to set */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr)	/*!< in: mtr */
{
	buf_block_t*	block;
	rec_t*		rec;
	ulint		err;

	block = btr_cur_get_block(cursor);
	rec = btr_cur_get_rec(cursor);

#ifdef UNIV_DEBUG
	if (btr_cur_print_record_ops && thr) {
		btr_cur_trx_report(thr_get_trx(thr), cursor->index,
				   "del mark ");
		rec_print(stderr, rec, cursor->index);
	}
#endif /* UNIV_DEBUG */

	err = lock_sec_rec_modify_check_and_lock(flags,
						 btr_cur_get_block(cursor),
						 rec, cursor->index, thr, mtr);
	if (err != DB_SUCCESS) {

		return(err);
	}

	ut_ad(!!page_rec_is_comp(rec)
	      == dict_table_is_comp(cursor->index->table));

	/* We do not need to reserve btr_search_latch, as the
	delete-mark flag is being updated in place and the adaptive
	hash index does not depend on it. */
	btr_rec_set_deleted_flag(rec, buf_block_get_page_zip(block), val);

	btr_cur_del_mark_set_sec_rec_log(rec, val, mtr);

	return(DB_SUCCESS);
}

/***********************************************************//**
Sets a secondary index record's delete mark to the given value. This
function is only used by the insert buffer merge mechanism. */
UNIV_INTERN
void
btr_cur_set_deleted_flag_for_ibuf(
/*==============================*/
	rec_t*		rec,		/*!< in/out: record */
	page_zip_des_t*	page_zip,	/*!< in/out: compressed page
					corresponding to rec, or NULL
					when the tablespace is
					uncompressed */
	ibool		val,		/*!< in: value to set */
	mtr_t*		mtr)		/*!< in/out: mini-transaction */
{
	/* We do not need to reserve btr_search_latch, as the page
	has just been read to the buffer pool and there cannot be
	a hash index to it.  Besides, the delete-mark flag is being
	updated in place and the adaptive hash index does not depend
	on it. */

	btr_rec_set_deleted_flag(rec, page_zip, val);

	btr_cur_del_mark_set_sec_rec_log(rec, val, mtr);
}

/*==================== B-TREE RECORD REMOVE =========================*/

/*************************************************************//**
Tries to compress a page of the tree if it seems useful. It is assumed
that mtr holds an x-latch on the tree and on the cursor page. To avoid
deadlocks, mtr must also own x-latches to brothers of page, if those
brothers exist. NOTE: it is assumed that the caller has reserved enough
free extents so that the compression will always succeed if done!
@return	TRUE if compression occurred */
UNIV_INTERN
ibool
btr_cur_compress_if_useful(
/*=======================*/
	btr_cur_t*	cursor,	/*!< in/out: cursor on the page to compress;
				cursor does not stay valid if !adjust and
				compression occurs */
	ibool		adjust,	/*!< in: TRUE if should adjust the
				cursor position even if compression occurs */
	mtr_t*		mtr)	/*!< in/out: mini-transaction */
{
	ut_ad(mtr_memo_contains(mtr,
				dict_index_get_lock(btr_cur_get_index(cursor)),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains(mtr, btr_cur_get_block(cursor),
				MTR_MEMO_PAGE_X_FIX));

	return(btr_cur_compress_recommendation(cursor, mtr)
	       && btr_compress(cursor, adjust, mtr));
}

/*******************************************************//**
Removes the record on which the tree cursor is positioned on a leaf page.
It is assumed that the mtr has an x-latch on the page where the cursor is
positioned, but no latch on the whole tree.
@return	TRUE if success, i.e., the page did not become too empty */
UNIV_INTERN
ibool
btr_cur_optimistic_delete(
/*======================*/
	btr_cur_t*	cursor,	/*!< in: cursor on leaf page, on the record to
				delete; cursor stays valid: if deletion
				succeeds, on function exit it points to the
				successor of the deleted record */
	mtr_t*		mtr)	/*!< in: mtr; if this function returns
				TRUE on a leaf page of a secondary
				index, the mtr must be committed
				before latching any further pages */
{
	buf_block_t*	block;
	rec_t*		rec;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	ibool		no_compress_needed;
	rec_offs_init(offsets_);

	ut_ad(mtr_memo_contains(mtr, btr_cur_get_block(cursor),
				MTR_MEMO_PAGE_X_FIX));
	/* This is intended only for leaf page deletions */

	block = btr_cur_get_block(cursor);

	ut_ad(page_is_leaf(buf_block_get_frame(block)));

	rec = btr_cur_get_rec(cursor);
	offsets = rec_get_offsets(rec, cursor->index, offsets,
				  ULINT_UNDEFINED, &heap);

	no_compress_needed = !rec_offs_any_extern(offsets)
		&& btr_cur_can_delete_without_compress(
			cursor, rec_offs_size(offsets), mtr);

	if (no_compress_needed) {

		page_t*		page	= buf_block_get_frame(block);
		page_zip_des_t*	page_zip= buf_block_get_page_zip(block);
		ulint		max_ins	= 0;

		lock_update_delete(block, rec);

		btr_search_update_hash_on_delete(cursor);

		if (!page_zip) {
			max_ins = page_get_max_insert_size_after_reorganize(
				page, 1);
		}
#ifdef UNIV_ZIP_DEBUG
		ut_a(!page_zip
		     || page_zip_validate(page_zip, page, cursor->index));
#endif /* UNIV_ZIP_DEBUG */
		page_cur_delete_rec(btr_cur_get_page_cur(cursor),
				    cursor->index, offsets, mtr);
#ifdef UNIV_ZIP_DEBUG
		ut_a(!page_zip
		     || page_zip_validate(page_zip, page, cursor->index));
#endif /* UNIV_ZIP_DEBUG */

		if (dict_index_is_clust(cursor->index)
		    || dict_index_is_ibuf(cursor->index)
		    || !page_is_leaf(page)) {
			/* The insert buffer does not handle
			inserts to clustered indexes, to
			non-leaf pages of secondary index B-trees,
			or to the insert buffer. */
		} else if (page_zip) {
			ibuf_update_free_bits_zip(block, mtr);
		} else {
			ibuf_update_free_bits_low(block, max_ins, mtr);
		}
	}

	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}

	return(no_compress_needed);
}

/*************************************************************//**
Removes the record on which the tree cursor is positioned. Tries
to compress the page if its fillfactor drops below a threshold
or if it is the only page on the level. It is assumed that mtr holds
an x-latch on the tree and on the cursor page. To avoid deadlocks,
mtr must also own x-latches to brothers of page, if those brothers
exist.
@return	TRUE if compression occurred */
UNIV_INTERN
ibool
btr_cur_pessimistic_delete(
/*=======================*/
	ulint*		err,	/*!< out: DB_SUCCESS or DB_OUT_OF_FILE_SPACE;
				the latter may occur because we may have
				to update node pointers on upper levels,
				and in the case of variable length keys
				these may actually grow in size */
	ibool		has_reserved_extents, /*!< in: TRUE if the
				caller has already reserved enough free
				extents so that he knows that the operation
				will succeed */
	btr_cur_t*	cursor,	/*!< in: cursor on the record to delete;
				if compression does not occur, the cursor
				stays valid: it points to successor of
				deleted record on function exit */
	enum trx_rb_ctx	rb_ctx,	/*!< in: rollback context */
	mtr_t*		mtr)	/*!< in: mtr */
{
	buf_block_t*	block;
	page_t*		page;
	page_zip_des_t*	page_zip;
	dict_index_t*	index;
	rec_t*		rec;
	dtuple_t*	node_ptr;
	ulint		n_extents	= 0;
	ulint		n_reserved;
	ibool		success;
	ibool		ret		= FALSE;
	ulint		level;
	mem_heap_t*	heap;
	ulint*		offsets;

	block = btr_cur_get_block(cursor);
	page = buf_block_get_frame(block);
	index = btr_cur_get_index(cursor);

	ut_ad(mtr_memo_contains(mtr, dict_index_get_lock(index),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	if (!has_reserved_extents) {
		/* First reserve enough free space for the file segments
		of the index tree, so that the node pointer updates will
		not fail because of lack of space */

		n_extents = cursor->tree_height / 32 + 1;

		success = fsp_reserve_free_extents(&n_reserved,
						   index->space,
						   n_extents,
						   FSP_CLEANING, mtr);
		if (!success) {
			*err = DB_OUT_OF_FILE_SPACE;

			return(FALSE);
		}
	}

	heap = mem_heap_create(1024);
	rec = btr_cur_get_rec(cursor);
	page_zip = buf_block_get_page_zip(block);
#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */

	offsets = rec_get_offsets(rec, index, NULL, ULINT_UNDEFINED, &heap);

	if (rec_offs_any_extern(offsets)) {
		btr_rec_free_externally_stored_fields(index,
						      rec, offsets, page_zip,
						      rb_ctx, mtr);
#ifdef UNIV_ZIP_DEBUG
		ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */
	}

	if (UNIV_UNLIKELY(page_get_n_recs(page) < 2)
	    && UNIV_UNLIKELY(dict_index_get_page(index)
			     != buf_block_get_page_no(block))) {

		/* If there is only one record, drop the whole page in
		btr_discard_page, if this is not the root page */

		btr_discard_page(cursor, mtr);

		*err = DB_SUCCESS;
		ret = TRUE;

		goto return_after_reservations;
	}

	lock_update_delete(block, rec);
	level = btr_page_get_level(page, mtr);

	if (level > 0
	    && UNIV_UNLIKELY(rec == page_rec_get_next(
				     page_get_infimum_rec(page)))) {

		rec_t*	next_rec = page_rec_get_next(rec);

		if (btr_page_get_prev(page, mtr) == FIL_NULL) {

			/* If we delete the leftmost node pointer on a
			non-leaf level, we must mark the new leftmost node
			pointer as the predefined minimum record */

			/* This will make page_zip_validate() fail until
			page_cur_delete_rec() completes.  This is harmless,
			because everything will take place within a single
			mini-transaction and because writing to the redo log
			is an atomic operation (performed by mtr_commit()). */
			btr_set_min_rec_mark(next_rec, mtr);
		} else {
			/* Otherwise, if we delete the leftmost node pointer
			on a page, we have to change the father node pointer
			so that it is equal to the new leftmost node pointer
			on the page */

			btr_node_ptr_delete(index, block, mtr);

			node_ptr = dict_index_build_node_ptr(
				index, next_rec, buf_block_get_page_no(block),
				heap, level);

			btr_insert_on_non_leaf_level(index,
						     level + 1, node_ptr, mtr);
		}
	}

	btr_search_update_hash_on_delete(cursor);

	page_cur_delete_rec(btr_cur_get_page_cur(cursor), index, offsets, mtr);
#ifdef UNIV_ZIP_DEBUG
	ut_a(!page_zip || page_zip_validate(page_zip, page, index));
#endif /* UNIV_ZIP_DEBUG */

	ut_ad(btr_check_node_ptr(index, block, mtr));

	*err = DB_SUCCESS;

return_after_reservations:
	mem_heap_free(heap);

	if (ret == FALSE) {
		ret = btr_cur_compress_if_useful(cursor, FALSE, mtr);
	}

	if (n_extents > 0) {
		fil_space_release_free_extents(index->space, n_reserved);
	}

	return(ret);
}

/*******************************************************************//**
Adds path information to the cursor for the current page, for which
the binary search has been performed. */
static
void
btr_cur_add_path_info(
/*==================*/
	btr_cur_t*	cursor,		/*!< in: cursor positioned on a page */
	ulint		height,		/*!< in: height of the page in tree;
					0 means leaf node */
	ulint		root_height)	/*!< in: root node height in tree */
{
	btr_path_t*	slot;
	rec_t*		rec;
	page_t*		page;

	ut_a(cursor->path_arr);

	if (root_height >= BTR_PATH_ARRAY_N_SLOTS - 1) {
		/* Do nothing; return empty path */

		slot = cursor->path_arr;
		slot->nth_rec = ULINT_UNDEFINED;

		return;
	}

	if (height == 0) {
		/* Mark end of slots for path */
		slot = cursor->path_arr + root_height + 1;
		slot->nth_rec = ULINT_UNDEFINED;
	}

	rec = btr_cur_get_rec(cursor);

	slot = cursor->path_arr + (root_height - height);

	page = page_align(rec);

	slot->nth_rec = page_rec_get_n_recs_before(rec);
	slot->n_recs = page_get_n_recs(page);
	slot->page_no = page_get_page_no(page);
	slot->page_level = btr_page_get_level_low(page);
}

/*******************************************************************//**
Estimate the number of rows between slot1 and slot2 for any level on a
B-tree. This function starts from slot1->page and reads a few pages to
the right, counting their records. If we reach slot2->page quickly then
we know exactly how many records there are between slot1 and slot2 and
we set is_n_rows_exact to TRUE. If we cannot reach slot2->page quickly
then we calculate the average number of records in the pages scanned
so far and assume that all pages that we did not scan up to slot2->page
contain the same number of records, then we multiply that average to
the number of pages between slot1->page and slot2->page (which is
n_rows_on_prev_level). In this case we set is_n_rows_exact to FALSE.
@return	number of rows (exact or estimated) */
static
ib_int64_t
btr_estimate_n_rows_in_range_on_level(
/*==================================*/
	dict_index_t*	index,			/*!< in: index */
	btr_path_t*	slot1,			/*!< in: left border */
	btr_path_t*	slot2,			/*!< in: right border */
	ib_int64_t	n_rows_on_prev_level,	/*!< in: number of rows
						on the previous level for the
						same descend paths; used to
						determine the numbe of pages
						on this level */
	ibool*		is_n_rows_exact)	/*!< out: TRUE if the returned
						value is exact i.e. not an
						estimation */
{
	ulint		space;
	ib_int64_t	n_rows;
	ulint		n_pages_read;
	ulint		page_no;
	ulint		zip_size;
	ulint		level;

	space = dict_index_get_space(index);

	n_rows = 0;
	n_pages_read = 0;

	/* Assume by default that we will scan all pages between
	slot1->page_no and slot2->page_no */
	*is_n_rows_exact = TRUE;

	/* add records from slot1->page_no which are to the right of
	the record which serves as a left border of the range, if any */
	if (slot1->nth_rec < slot1->n_recs) {
		n_rows += slot1->n_recs - slot1->nth_rec;
	}

	/* add records from slot2->page_no which are to the left of
	the record which servers as a right border of the range, if any */
	if (slot2->nth_rec > 1) {
		n_rows += slot2->nth_rec - 1;
	}

	/* count the records in the pages between slot1->page_no and
	slot2->page_no (non inclusive), if any */

	zip_size = fil_space_get_zip_size(space);

	/* Do not read more than this number of pages in order not to hurt
	performance with this code which is just an estimation. If we read
	this many pages before reaching slot2->page_no then we estimate the
	average from the pages scanned so far */
#	define N_PAGES_READ_LIMIT	10

	page_no = slot1->page_no;
	level = slot1->page_level;

	do {
		mtr_t		mtr;
		page_t*		page;
		buf_block_t*	block;

		mtr_start(&mtr);

		/* Fetch the page. Because we are not holding the
		index->lock, the tree may have changed and we may be
		attempting to read a page that is no longer part of
		the B-tree. We pass BUF_GET_POSSIBLY_FREED in order to
		silence a debug assertion about this. */
		block = buf_page_get_gen(space, zip_size, page_no, RW_S_LATCH,
					 NULL, BUF_GET_POSSIBLY_FREED,
					 __FILE__, __LINE__, &mtr);

		page = buf_block_get_frame(block);

		/* It is possible that the tree has been reorganized in the
		meantime and this is a different page. If this happens the
		calculated estimate will be bogus, which is not fatal as
		this is only an estimate. We are sure that a page with
		page_no exists because InnoDB never frees pages, only
		reuses them. */
		if (fil_page_get_type(page) != FIL_PAGE_INDEX
		    || btr_page_get_index_id(page) != index->id
		    || btr_page_get_level_low(page) != level) {

			/* The page got reused for something else */
			mtr_commit(&mtr);
			goto inexact;
		}

		/* It is possible but highly unlikely that the page was
		originally written by an old version of InnoDB that did
		not initialize FIL_PAGE_TYPE on other than B-tree pages.
		For example, this could be an almost-empty BLOB page
		that happens to contain the magic values in the fields
		that we checked above. */

		n_pages_read++;

		if (page_no != slot1->page_no) {
			/* Do not count the records on slot1->page_no,
			we already counted them before this loop. */
			n_rows += page_get_n_recs(page);
		}

		page_no = btr_page_get_next(page, &mtr);

		mtr_commit(&mtr);

		if (n_pages_read == N_PAGES_READ_LIMIT
		    || page_no == FIL_NULL) {
			/* Either we read too many pages or
			we reached the end of the level without passing
			through slot2->page_no, the tree must have changed
			in the meantime */
			goto inexact;
		}

	} while (page_no != slot2->page_no);

	return(n_rows);

inexact:

	*is_n_rows_exact = FALSE;

	/* We did interrupt before reaching slot2->page */

	if (n_pages_read > 0) {
		/* The number of pages on this level is
		n_rows_on_prev_level, multiply it by the
		average number of recs per page so far */
		n_rows = n_rows_on_prev_level
			* n_rows / n_pages_read;
	} else {
		/* The tree changed before we could even
		start with slot1->page_no */
		n_rows = 10;
	}

	return(n_rows);
}

/*******************************************************************//**
Estimates the number of rows in a given index range.
@return	estimated number of rows */
UNIV_INTERN
ib_int64_t
btr_estimate_n_rows_in_range(
/*=========================*/
	dict_index_t*	index,	/*!< in: index */
	const dtuple_t*	tuple1,	/*!< in: range start, may also be empty tuple */
	ulint		mode1,	/*!< in: search mode for range start */
	const dtuple_t*	tuple2,	/*!< in: range end, may also be empty tuple */
	ulint		mode2)	/*!< in: search mode for range end */
{
	btr_path_t	path1[BTR_PATH_ARRAY_N_SLOTS];
	btr_path_t	path2[BTR_PATH_ARRAY_N_SLOTS];
	btr_cur_t	cursor;
	btr_path_t*	slot1;
	btr_path_t*	slot2;
	ibool		diverged;
	ibool		diverged_lot;
	ulint		divergence_level;
	ib_int64_t	n_rows;
	ibool		is_n_rows_exact;
	ulint		i;
	mtr_t		mtr;

	mtr_start(&mtr);

	cursor.path_arr = path1;

	if (dtuple_get_n_fields(tuple1) > 0) {

		btr_cur_search_to_nth_level(index, 0, tuple1, mode1,
					    BTR_SEARCH_LEAF | BTR_ESTIMATE,
					    &cursor, 0,
					    __FILE__, __LINE__, &mtr);
	} else {
		btr_cur_open_at_index_side(TRUE, index,
					   BTR_SEARCH_LEAF | BTR_ESTIMATE,
					   &cursor, &mtr);
	}

	mtr_commit(&mtr);

	mtr_start(&mtr);

	cursor.path_arr = path2;

	if (dtuple_get_n_fields(tuple2) > 0) {

		btr_cur_search_to_nth_level(index, 0, tuple2, mode2,
					    BTR_SEARCH_LEAF | BTR_ESTIMATE,
					    &cursor, 0,
					    __FILE__, __LINE__, &mtr);
	} else {
		btr_cur_open_at_index_side(FALSE, index,
					   BTR_SEARCH_LEAF | BTR_ESTIMATE,
					   &cursor, &mtr);
	}

	mtr_commit(&mtr);

	/* We have the path information for the range in path1 and path2 */

	n_rows = 1;
	is_n_rows_exact = TRUE;
	diverged = FALSE;	    /* This becomes true when the path is not
				    the same any more */
	diverged_lot = FALSE;	    /* This becomes true when the paths are
				    not the same or adjacent any more */
	divergence_level = 1000000; /* This is the level where paths diverged
				    a lot */
	for (i = 0; ; i++) {
		ut_ad(i < BTR_PATH_ARRAY_N_SLOTS);

		slot1 = path1 + i;
		slot2 = path2 + i;

		if (slot1->nth_rec == ULINT_UNDEFINED
		    || slot2->nth_rec == ULINT_UNDEFINED) {

			if (i > divergence_level + 1 && !is_n_rows_exact) {
				/* In trees whose height is > 1 our algorithm
				tends to underestimate: multiply the estimate
				by 2: */

				n_rows = n_rows * 2;
			}

			DBUG_EXECUTE_IF("bug14007649", return(n_rows););

			/* Do not estimate the number of rows in the range
			to over 1 / 2 of the estimated rows in the whole
			table */

			if (n_rows > index->table->stat_n_rows / 2
			    && !is_n_rows_exact) {

				n_rows = index->table->stat_n_rows / 2;

				/* If there are just 0 or 1 rows in the table,
				then we estimate all rows are in the range */

				if (n_rows == 0) {
					n_rows = index->table->stat_n_rows;
				}
			}

			return(n_rows);
		}

		if (!diverged && slot1->nth_rec != slot2->nth_rec) {

			diverged = TRUE;

			if (slot1->nth_rec < slot2->nth_rec) {
				n_rows = slot2->nth_rec - slot1->nth_rec;

				if (n_rows > 1) {
					diverged_lot = TRUE;
					divergence_level = i;
				}
			} else {
				/* It is possible that
				slot1->nth_rec >= slot2->nth_rec
				if, for example, we have a single page
				tree which contains (inf, 5, 6, supr)
				and we select where x > 20 and x < 30;
				in this case slot1->nth_rec will point
				to the supr record and slot2->nth_rec
				will point to 6 */
				n_rows = 0;
			}

		} else if (diverged && !diverged_lot) {

			if (slot1->nth_rec < slot1->n_recs
			    || slot2->nth_rec > 1) {

				diverged_lot = TRUE;
				divergence_level = i;

				n_rows = 0;

				if (slot1->nth_rec < slot1->n_recs) {
					n_rows += slot1->n_recs
						- slot1->nth_rec;
				}

				if (slot2->nth_rec > 1) {
					n_rows += slot2->nth_rec - 1;
				}
			}
		} else if (diverged_lot) {

			n_rows = btr_estimate_n_rows_in_range_on_level(
				index, slot1, slot2, n_rows,
				&is_n_rows_exact);
		}
	}
}

/*******************************************************************//**
Record the number of non_null key values in a given index for
each n-column prefix of the index where n < dict_index_get_n_unique(index).
The estimates are eventually stored in the array:
index->stat_n_non_null_key_vals. */
static
void
btr_record_not_null_field_in_rec(
/*=============================*/
	ulint		n_unique,	/*!< in: dict_index_get_n_unique(index),
					number of columns uniquely determine
					an index entry */
	const ulint*	offsets,	/*!< in: rec_get_offsets(rec, index),
					its size could be for all fields or
					that of "n_unique" */
	ib_int64_t*	n_not_null)	/*!< in/out: array to record number of
					not null rows for n-column prefix */
{
	ulint	i;

	ut_ad(rec_offs_n_fields(offsets) >= n_unique);

	if (n_not_null == NULL) {
		return;
	}

	for (i = 0; i < n_unique; i++) {
		if (rec_offs_nth_sql_null(offsets, i)) {
			break;
		}

		n_not_null[i]++;
	}
}

/*******************************************************************//**
Estimates the number of different key values in a given index, for
each n-column prefix of the index where n <= dict_index_get_n_unique(index).
The estimates are stored in the array index->stat_n_diff_key_vals.
If innodb_stats_method is "nulls_ignored", we also record the number of
non-null values for each prefix and store the estimates in
array index->stat_n_non_null_key_vals. */
UNIV_INTERN
void
btr_estimate_number_of_different_key_vals(
/*======================================*/
	dict_index_t*	index)	/*!< in: index */
{
	btr_cur_t	cursor;
	page_t*		page;
	rec_t*		rec;
	ulint		n_cols;
	ulint		matched_fields;
	ulint		matched_bytes;
	ib_int64_t*	n_diff;
	ib_int64_t*	n_not_null;
	ibool		stats_null_not_equal;
	ullint		n_sample_pages; /* number of pages to sample */
	ulint		not_empty_flag	= 0;
	ulint		total_external_size = 0;
	ulint		i;
	ulint		j;
	ullint		add_on;
	mtr_t		mtr;
	mem_heap_t*	heap		= NULL;
	ulint*		offsets_rec	= NULL;
	ulint*		offsets_next_rec = NULL;

	n_cols = dict_index_get_n_unique(index);

	heap = mem_heap_create((sizeof *n_diff + sizeof *n_not_null)
			       * (n_cols + 1)
			       + dict_index_get_n_fields(index)
			       * (sizeof *offsets_rec
				  + sizeof *offsets_next_rec));

	n_diff = mem_heap_zalloc(heap, (n_cols + 1) * sizeof(ib_int64_t));

	n_not_null = NULL;

	/* Check srv_innodb_stats_method setting, and decide whether we
	need to record non-null value and also decide if NULL is
	considered equal (by setting stats_null_not_equal value) */
	switch (srv_innodb_stats_method) {
	case SRV_STATS_NULLS_IGNORED:
		n_not_null = mem_heap_zalloc(heap, (n_cols + 1)
					     * sizeof *n_not_null);
		/* fall through */

	case SRV_STATS_NULLS_UNEQUAL:
		/* for both SRV_STATS_NULLS_IGNORED and SRV_STATS_NULLS_UNEQUAL
		case, we will treat NULLs as unequal value */
		stats_null_not_equal = TRUE;
		break;

	case SRV_STATS_NULLS_EQUAL:
		stats_null_not_equal = FALSE;
		break;

	default:
		ut_error;
        }

	/* It makes no sense to test more pages than are contained
	in the index, thus we lower the number if it is too high */
	if (srv_stats_sample_pages > index->stat_index_size) {
		if (index->stat_index_size > 0) {
			n_sample_pages = index->stat_index_size;
		} else {
			n_sample_pages = 1;
		}
	} else {
		n_sample_pages = srv_stats_sample_pages;
	}

	/* We sample some pages in the index to get an estimate */

	for (i = 0; i < n_sample_pages; i++) {
		mtr_start(&mtr);

		btr_cur_open_at_rnd_pos(index, BTR_SEARCH_LEAF, &cursor, &mtr);

		/* Count the number of different key values for each prefix of
		the key on this index page. If the prefix does not determine
		the index record uniquely in the B-tree, then we subtract one
		because otherwise our algorithm would give a wrong estimate
		for an index where there is just one key value. */

		page = btr_cur_get_page(&cursor);

		rec = page_rec_get_next(page_get_infimum_rec(page));

		if (!page_rec_is_supremum(rec)) {
			not_empty_flag = 1;
			offsets_rec = rec_get_offsets(rec, index, offsets_rec,
						      ULINT_UNDEFINED, &heap);

			if (n_not_null) {
				btr_record_not_null_field_in_rec(
					n_cols, offsets_rec, n_not_null);
			}
		}

		while (!page_rec_is_supremum(rec)) {
			rec_t*	next_rec = page_rec_get_next(rec);
			if (page_rec_is_supremum(next_rec)) {
				total_external_size +=
					btr_rec_get_externally_stored_len(
						rec, offsets_rec);
				break;
			}

			matched_fields = 0;
			matched_bytes = 0;
			offsets_next_rec = rec_get_offsets(next_rec, index,
							   offsets_next_rec,
							   ULINT_UNDEFINED,
							   &heap);

			cmp_rec_rec_with_match(rec, next_rec,
					       offsets_rec, offsets_next_rec,
					       index, stats_null_not_equal,
					       &matched_fields,
					       &matched_bytes);

			for (j = matched_fields + 1; j <= n_cols; j++) {
				/* We add one if this index record has
				a different prefix from the previous */

				n_diff[j]++;
			}

			if (n_not_null) {
				btr_record_not_null_field_in_rec(
					n_cols, offsets_next_rec, n_not_null);
			}

			total_external_size
				+= btr_rec_get_externally_stored_len(
					rec, offsets_rec);

			rec = next_rec;
			/* Initialize offsets_rec for the next round
			and assign the old offsets_rec buffer to
			offsets_next_rec. */
			{
				ulint*	offsets_tmp = offsets_rec;
				offsets_rec = offsets_next_rec;
				offsets_next_rec = offsets_tmp;
			}
		}


		if (n_cols == dict_index_get_n_unique_in_tree(index)) {

			/* If there is more than one leaf page in the tree,
			we add one because we know that the first record
			on the page certainly had a different prefix than the
			last record on the previous index page in the
			alphabetical order. Before this fix, if there was
			just one big record on each clustered index page, the
			algorithm grossly underestimated the number of rows
			in the table. */

			if (btr_page_get_prev(page, &mtr) != FIL_NULL
			    || btr_page_get_next(page, &mtr) != FIL_NULL) {

				n_diff[n_cols]++;
			}
		}

		mtr_commit(&mtr);
	}

	/* If we saw k borders between different key values on
	n_sample_pages leaf pages, we can estimate how many
	there will be in index->stat_n_leaf_pages */

	/* We must take into account that our sample actually represents
	also the pages used for external storage of fields (those pages are
	included in index->stat_n_leaf_pages) */

	for (j = 0; j <= n_cols; j++) {
		index->stat_n_diff_key_vals[j]
			= BTR_TABLE_STATS_FROM_SAMPLE(
				n_diff[j], index, n_sample_pages,
				total_external_size, not_empty_flag); 

		/* If the tree is small, smaller than
		10 * n_sample_pages + total_external_size, then
		the above estimate is ok. For bigger trees it is common that we
		do not see any borders between key values in the few pages
		we pick. But still there may be n_sample_pages
		different key values, or even more. Let us try to approximate
		that: */

		add_on = index->stat_n_leaf_pages
			/ (10 * (n_sample_pages
				 + total_external_size));

		if (add_on > n_sample_pages) {
			add_on = n_sample_pages;
		}

		index->stat_n_diff_key_vals[j] += add_on;

		/* Update the stat_n_non_null_key_vals[] with our
		sampled result. stat_n_non_null_key_vals[] is created
		and initialized to zero in dict_index_add_to_cache(),
		along with stat_n_diff_key_vals[] array */
		if (n_not_null != NULL && (j < n_cols)) {
			index->stat_n_non_null_key_vals[j] =
				 BTR_TABLE_STATS_FROM_SAMPLE(
					n_not_null[j], index, n_sample_pages,
					total_external_size, not_empty_flag);
		}
	}

	mem_heap_free(heap);
}

/*================== EXTERNAL STORAGE OF BIG FIELDS ===================*/

/***********************************************************//**
Gets the offset of the pointer to the externally stored part of a field.
@return	offset of the pointer to the externally stored part */
static
ulint
btr_rec_get_field_ref_offs(
/*=======================*/
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	ulint		n)	/*!< in: index of the external field */
{
	ulint	field_ref_offs;
	ulint	local_len;

	ut_a(rec_offs_nth_extern(offsets, n));
	field_ref_offs = rec_get_nth_field_offs(offsets, n, &local_len);
	ut_a(local_len != UNIV_SQL_NULL);
	ut_a(local_len >= BTR_EXTERN_FIELD_REF_SIZE);

	return(field_ref_offs + local_len - BTR_EXTERN_FIELD_REF_SIZE);
}

/** Gets a pointer to the externally stored part of a field.
@param rec	record
@param offsets	rec_get_offsets(rec)
@param n	index of the externally stored field
@return pointer to the externally stored part */
#define btr_rec_get_field_ref(rec, offsets, n)			\
	((rec) + btr_rec_get_field_ref_offs(offsets, n))

/***********************************************************//**
Gets the externally stored size of a record, in units of a database page.
@return	externally stored part, in units of a database page */
static
ulint
btr_rec_get_externally_stored_len(
/*==============================*/
	const rec_t*	rec,	/*!< in: record */
	const ulint*	offsets)/*!< in: array returned by rec_get_offsets() */
{
	ulint	n_fields;
	ulint	total_extern_len = 0;
	ulint	i;

	ut_ad(!rec_offs_comp(offsets) || !rec_get_node_ptr_flag(rec));

	if (!rec_offs_any_extern(offsets)) {
		return(0);
	}

	n_fields = rec_offs_n_fields(offsets);

	for (i = 0; i < n_fields; i++) {
		if (rec_offs_nth_extern(offsets, i)) {

			ulint	extern_len = mach_read_from_4(
				btr_rec_get_field_ref(rec, offsets, i)
				+ BTR_EXTERN_LEN + 4);

			total_extern_len += ut_calc_align(extern_len,
							  UNIV_PAGE_SIZE);
		}
	}

	return(total_extern_len / UNIV_PAGE_SIZE);
}

/*******************************************************************//**
Sets the ownership bit of an externally stored field in a record. */
static
void
btr_cur_set_ownership_of_extern_field(
/*==================================*/
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose uncompressed
				part will be updated, or NULL */
	rec_t*		rec,	/*!< in/out: clustered index record */
	dict_index_t*	index,	/*!< in: index of the page */
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	ulint		i,	/*!< in: field number */
	ibool		val,	/*!< in: value to set */
	mtr_t*		mtr)	/*!< in: mtr, or NULL if not logged */
{
	byte*	data;
	ulint	local_len;
	ulint	byte_val;

	data = rec_get_nth_field(rec, offsets, i, &local_len);
	ut_ad(rec_offs_nth_extern(offsets, i));
	ut_a(local_len >= BTR_EXTERN_FIELD_REF_SIZE);

	local_len -= BTR_EXTERN_FIELD_REF_SIZE;

	byte_val = mach_read_from_1(data + local_len + BTR_EXTERN_LEN);

	if (val) {
		byte_val = byte_val & (~BTR_EXTERN_OWNER_FLAG);
	} else {
#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
		ut_a(!(byte_val & BTR_EXTERN_OWNER_FLAG));
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
		byte_val = byte_val | BTR_EXTERN_OWNER_FLAG;
	}

	if (page_zip) {
		mach_write_to_1(data + local_len + BTR_EXTERN_LEN, byte_val);
		page_zip_write_blob_ptr(page_zip, rec, index, offsets, i, mtr);
	} else if (mtr != NULL) {

		mlog_write_ulint(data + local_len + BTR_EXTERN_LEN, byte_val,
				 MLOG_1BYTE, mtr);
	} else {
		mach_write_to_1(data + local_len + BTR_EXTERN_LEN, byte_val);
	}

	btr_blob_dbg_owner(rec, index, offsets, i, val);
}

/*******************************************************************//**
Marks non-updated off-page fields as disowned by this record. The ownership
must be transferred to the updated record which is inserted elsewhere in the
index tree. In purge only the owner of externally stored field is allowed
to free the field. */
UNIV_INTERN
void
btr_cur_disown_inherited_fields(
/*============================*/
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose uncompressed
				part will be updated, or NULL */
	rec_t*		rec,	/*!< in/out: record in a clustered index */
	dict_index_t*	index,	/*!< in: index of the page */
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	const upd_t*	update,	/*!< in: update vector */
	mtr_t*		mtr)	/*!< in/out: mini-transaction */
{
	ulint	i;

	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(!rec_offs_comp(offsets) || !rec_get_node_ptr_flag(rec));
	ut_ad(rec_offs_any_extern(offsets));
	ut_ad(mtr);

	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
		if (rec_offs_nth_extern(offsets, i)
		    && !upd_get_field_by_field_no(update, i)) {
			btr_cur_set_ownership_of_extern_field(
				page_zip, rec, index, offsets, i, FALSE, mtr);
		}
	}
}

/*******************************************************************//**
Marks all extern fields in a record as owned by the record. This function
should be called if the delete mark of a record is removed: a not delete
marked record always owns all its extern fields. */
static
void
btr_cur_unmark_extern_fields(
/*=========================*/
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose uncompressed
				part will be updated, or NULL */
	rec_t*		rec,	/*!< in/out: record in a clustered index */
	dict_index_t*	index,	/*!< in: index of the page */
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	mtr_t*		mtr)	/*!< in: mtr, or NULL if not logged */
{
	ulint	n;
	ulint	i;

	ut_ad(!rec_offs_comp(offsets) || !rec_get_node_ptr_flag(rec));
	n = rec_offs_n_fields(offsets);

	if (!rec_offs_any_extern(offsets)) {

		return;
	}

	for (i = 0; i < n; i++) {
		if (rec_offs_nth_extern(offsets, i)) {

			btr_cur_set_ownership_of_extern_field(
				page_zip, rec, index, offsets, i, TRUE, mtr);
		}
	}
}

/*******************************************************************//**
Flags the data tuple fields that are marked as extern storage in the
update vector.  We use this function to remember which fields we must
mark as extern storage in a record inserted for an update.
@return	number of flagged external columns */
UNIV_INTERN
ulint
btr_push_update_extern_fields(
/*==========================*/
	dtuple_t*	tuple,	/*!< in/out: data tuple */
	const upd_t*	update,	/*!< in: update vector */
	mem_heap_t*	heap)	/*!< in: memory heap */
{
	ulint			n_pushed	= 0;
	ulint			n;
	const upd_field_t*	uf;

	ut_ad(tuple);
	ut_ad(update);

	uf = update->fields;
	n = upd_get_n_fields(update);

	for (; n--; uf++) {
		if (dfield_is_ext(&uf->new_val)) {
			dfield_t*	field
				= dtuple_get_nth_field(tuple, uf->field_no);

			if (!dfield_is_ext(field)) {
				dfield_set_ext(field);
				n_pushed++;
			}

			switch (uf->orig_len) {
				byte*	data;
				ulint	len;
				byte*	buf;
			case 0:
				break;
			case BTR_EXTERN_FIELD_REF_SIZE:
				/* Restore the original locally stored
				part of the column.  In the undo log,
				InnoDB writes a longer prefix of externally
				stored columns, so that column prefixes
				in secondary indexes can be reconstructed. */
				dfield_set_data(field, (byte*) dfield_get_data(field)
						+ dfield_get_len(field)
						- BTR_EXTERN_FIELD_REF_SIZE,
						BTR_EXTERN_FIELD_REF_SIZE);
				dfield_set_ext(field);
				break;
			default:
				/* Reconstruct the original locally
				stored part of the column.  The data
				will have to be copied. */
				ut_a(uf->orig_len > BTR_EXTERN_FIELD_REF_SIZE);

				data = dfield_get_data(field);
				len = dfield_get_len(field);

				buf = mem_heap_alloc(heap, uf->orig_len);
				/* Copy the locally stored prefix. */
				memcpy(buf, data,
				       uf->orig_len
				       - BTR_EXTERN_FIELD_REF_SIZE);
				/* Copy the BLOB pointer. */
				memcpy(buf + uf->orig_len
				       - BTR_EXTERN_FIELD_REF_SIZE,
				       data + len - BTR_EXTERN_FIELD_REF_SIZE,
				       BTR_EXTERN_FIELD_REF_SIZE);

				dfield_set_data(field, buf, uf->orig_len);
				dfield_set_ext(field);
			}
		}
	}

	return(n_pushed);
}

/*******************************************************************//**
Returns the length of a BLOB part stored on the header page.
@return	part length */
static
ulint
btr_blob_get_part_len(
/*==================*/
	const byte*	blob_header)	/*!< in: blob header */
{
	return(mach_read_from_4(blob_header + BTR_BLOB_HDR_PART_LEN));
}

/*******************************************************************//**
Returns the page number where the next BLOB part is stored.
@return	page number or FIL_NULL if no more pages */
static
ulint
btr_blob_get_next_page_no(
/*======================*/
	const byte*	blob_header)	/*!< in: blob header */
{
	return(mach_read_from_4(blob_header + BTR_BLOB_HDR_NEXT_PAGE_NO));
}

/*******************************************************************//**
Deallocate a buffer block that was reserved for a BLOB part. */
static
void
btr_blob_free(
/*==========*/
	buf_block_t*	block,	/*!< in: buffer block */
	ibool		all,	/*!< in: TRUE=remove also the compressed page
				if there is one */
	mtr_t*		mtr)	/*!< in: mini-transaction to commit */
{
	buf_pool_t*	buf_pool = buf_pool_from_block(block);
	ulint		space	= buf_block_get_space(block);
	ulint		page_no	= buf_block_get_page_no(block);

	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));

	mtr_commit(mtr);

	buf_pool_mutex_enter(buf_pool);
	mutex_enter(&block->mutex);

	/* Only free the block if it is still allocated to
	the same file page. */

	if (buf_block_get_state(block)
	    == BUF_BLOCK_FILE_PAGE
	    && buf_block_get_space(block) == space
	    && buf_block_get_page_no(block) == page_no) {

		if (!buf_LRU_free_block(&block->page, all)
		    && all && block->page.zip.data) {
			/* Attempt to deallocate the uncompressed page
			if the whole block cannot be deallocted. */

			buf_LRU_free_block(&block->page, FALSE);
		}
	}

	buf_pool_mutex_exit(buf_pool);
	mutex_exit(&block->mutex);
}

/*******************************************************************//**
Stores the fields in big_rec_vec to the tablespace and puts pointers to
them in rec.  The extern flags in rec will have to be set beforehand.
The fields are stored on pages allocated from leaf node
file segment of the index tree.
@return	DB_SUCCESS or DB_OUT_OF_FILE_SPACE */
UNIV_INTERN
enum db_err
btr_store_big_rec_extern_fields(
/*============================*/
	dict_index_t*	index,		/*!< in: index of rec; the index tree
					MUST be X-latched */
	buf_block_t*	rec_block,	/*!< in/out: block containing rec */
	rec_t*		rec,		/*!< in/out: record */
	const ulint*	offsets,	/*!< in: rec_get_offsets(rec, index);
					the "external storage" flags in offsets
					will not correspond to rec when
					this function returns */
	const big_rec_t*big_rec_vec,	/*!< in: vector containing fields
					to be stored externally */
	mtr_t*		btr_mtr,	/*!< in: mtr containing the
					latches to the clustered index */
	enum blob_op	op)		/*! in: operation code */
{
	ulint		rec_page_no;
	byte*		field_ref;
	ulint		extern_len;
	ulint		store_len;
	ulint		page_no;
	ulint		space_id;
	ulint		zip_size;
	ulint		prev_page_no;
	ulint		hint_page_no;
	ulint		i;
	mtr_t		mtr;
	mtr_t*		alloc_mtr;
	mem_heap_t*	heap = NULL;
	page_zip_des_t*	page_zip;
	z_stream	c_stream;
	buf_block_t**	freed_pages	= NULL;
	ulint		n_freed_pages	= 0;
	enum db_err	error		= DB_SUCCESS;

	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(rec_offs_any_extern(offsets));
	ut_ad(btr_mtr);
	ut_ad(mtr_memo_contains(btr_mtr, dict_index_get_lock(index),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains(btr_mtr, rec_block, MTR_MEMO_PAGE_X_FIX));
	ut_ad(buf_block_get_frame(rec_block) == page_align(rec));
	ut_a(dict_index_is_clust(index));

	page_zip = buf_block_get_page_zip(rec_block);
	ut_a(dict_table_zip_size(index->table)
	     == buf_block_get_zip_size(rec_block));

	space_id = buf_block_get_space(rec_block);
	zip_size = buf_block_get_zip_size(rec_block);
	rec_page_no = buf_block_get_page_no(rec_block);
	ut_a(fil_page_get_type(page_align(rec)) == FIL_PAGE_INDEX);

	if (page_zip) {
		int	err;

		/* Zlib deflate needs 128 kilobytes for the default
		window size, plus 512 << memLevel, plus a few
		kilobytes for small objects.  We use reduced memLevel
		to limit the memory consumption, and preallocate the
		heap, hoping to avoid memory fragmentation. */
		heap = mem_heap_create(250000);
		page_zip_set_alloc(&c_stream, heap);

		err = deflateInit2(&c_stream, Z_DEFAULT_COMPRESSION,
				   Z_DEFLATED, 15, 7, Z_DEFAULT_STRATEGY);
		ut_a(err == Z_OK);
	}

	if (btr_blob_op_is_update(op)) {
		/* Avoid reusing pages that have been previously freed
		in btr_mtr. */
		if (btr_mtr->n_freed_pages) {
			if (heap == NULL) {
				heap = mem_heap_create(
					btr_mtr->n_freed_pages
					* sizeof *freed_pages);
			}

			freed_pages = mem_heap_alloc(
				heap,
				btr_mtr->n_freed_pages
				* sizeof *freed_pages);
			n_freed_pages = 0;
		}

		/* Because btr_mtr will be committed after mtr, it is
		possible that the tablespace has been extended when
		the B-tree record was updated or inserted, or it will
		be extended while allocating pages for big_rec.

		TODO: In mtr (not btr_mtr), write a redo log record
		about extending the tablespace to its current size,
		and remember the current size. Whenever the tablespace
		grows as pages are allocated, write further redo log
		records to mtr. (Currently tablespace extension is not
		covered by the redo log. If it were, the record would
		only be written to btr_mtr, which is committed after
		mtr.) */
		alloc_mtr = btr_mtr;
	} else {
		/* Use the local mtr for allocations. */
		alloc_mtr = &mtr;
	}

#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
	/* All pointers to externally stored columns in the record
	must either be zero or they must be pointers to inherited
	columns, owned by this record or an earlier record version. */
	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
		if (!rec_offs_nth_extern(offsets, i)) {
			continue;
		}
		field_ref = btr_rec_get_field_ref(rec, offsets, i);

		ut_a(!(field_ref[BTR_EXTERN_LEN] & BTR_EXTERN_OWNER_FLAG));
		/* Either this must be an update in place,
		or the BLOB must be inherited, or the BLOB pointer
		must be zero (will be written in this function). */
		ut_a(op == BTR_STORE_UPDATE
		     || (field_ref[BTR_EXTERN_LEN] & BTR_EXTERN_INHERITED_FLAG)
		     || !memcmp(field_ref, field_ref_zero,
				BTR_EXTERN_FIELD_REF_SIZE));
	}
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
	/* We have to create a file segment to the tablespace
	for each field and put the pointer to the field in rec */

	for (i = 0; i < big_rec_vec->n_fields; i++) {
		field_ref = btr_rec_get_field_ref(
			rec, offsets, big_rec_vec->fields[i].field_no);
#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
		/* A zero BLOB pointer should have been initially inserted. */
		ut_a(!memcmp(field_ref, field_ref_zero,
			     BTR_EXTERN_FIELD_REF_SIZE));
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
		extern_len = big_rec_vec->fields[i].len;
		UNIV_MEM_ASSERT_RW(big_rec_vec->fields[i].data,
				   extern_len);

		ut_a(extern_len > 0);

		prev_page_no = FIL_NULL;

		if (page_zip) {
			int	err = deflateReset(&c_stream);
			ut_a(err == Z_OK);

			c_stream.next_in = (void*) big_rec_vec->fields[i].data;
			c_stream.avail_in = extern_len;
		}

		for (;;) {
			buf_block_t*	block;
			page_t*		page;

			mtr_start(&mtr);

			if (prev_page_no == FIL_NULL) {
				hint_page_no = 1 + rec_page_no;
			} else {
				hint_page_no = prev_page_no + 1;
			}

alloc_another:
			block = btr_page_alloc(index, hint_page_no,
					       FSP_NO_DIR, 0, alloc_mtr, &mtr);
			if (UNIV_UNLIKELY(block == NULL)) {
				mtr_commit(&mtr);
				error = DB_OUT_OF_FILE_SPACE;
				goto func_exit;
			}

			if (rw_lock_get_x_lock_count(&block->lock) > 1) {
				/* This page must have been freed in
				btr_mtr previously. Put it aside, and
				allocate another page for the BLOB data. */
				ut_ad(alloc_mtr == btr_mtr);
				ut_ad(btr_blob_op_is_update(op));
				ut_ad(n_freed_pages < btr_mtr->n_freed_pages);
				freed_pages[n_freed_pages++] = block;
				goto alloc_another;
			}

			page_no = buf_block_get_page_no(block);
			page = buf_block_get_frame(block);

			if (prev_page_no != FIL_NULL) {
				buf_block_t*	prev_block;
				page_t*		prev_page;

				prev_block = buf_page_get(space_id, zip_size,
							  prev_page_no,
							  RW_X_LATCH, &mtr);
				buf_block_dbg_add_level(prev_block,
							SYNC_EXTERN_STORAGE);
				prev_page = buf_block_get_frame(prev_block);

				if (page_zip) {
					mlog_write_ulint(
						prev_page + FIL_PAGE_NEXT,
						page_no, MLOG_4BYTES, &mtr);
					memcpy(buf_block_get_page_zip(
						       prev_block)
					       ->data + FIL_PAGE_NEXT,
					       prev_page + FIL_PAGE_NEXT, 4);
				} else {
					mlog_write_ulint(
						prev_page + FIL_PAGE_DATA
						+ BTR_BLOB_HDR_NEXT_PAGE_NO,
						page_no, MLOG_4BYTES, &mtr);
				}

			}

			if (page_zip) {
				int		err;
				page_zip_des_t*	blob_page_zip;

				/* Write FIL_PAGE_TYPE to the redo log
				separately, before logging any other
				changes to the page, so that the debug
				assertions in
				recv_parse_or_apply_log_rec_body() can
				be made simpler.  Before InnoDB Plugin
				1.0.4, the initialization of
				FIL_PAGE_TYPE was logged as part of
				the mlog_log_string() below. */

				mlog_write_ulint(page + FIL_PAGE_TYPE,
						 prev_page_no == FIL_NULL
						 ? FIL_PAGE_TYPE_ZBLOB
						 : FIL_PAGE_TYPE_ZBLOB2,
						 MLOG_2BYTES, &mtr);

				c_stream.next_out = page
					+ FIL_PAGE_DATA;
				c_stream.avail_out
					= page_zip_get_size(page_zip)
					- FIL_PAGE_DATA;

				err = deflate(&c_stream, Z_FINISH);
				ut_a(err == Z_OK || err == Z_STREAM_END);
				ut_a(err == Z_STREAM_END
				     || c_stream.avail_out == 0);

				/* Write the "next BLOB page" pointer */
				mlog_write_ulint(page + FIL_PAGE_NEXT,
						 FIL_NULL, MLOG_4BYTES, &mtr);
				/* Initialize the unused "prev page" pointer */
				mlog_write_ulint(page + FIL_PAGE_PREV,
						 FIL_NULL, MLOG_4BYTES, &mtr);
				/* Write a back pointer to the record
				into the otherwise unused area.  This
				information could be useful in
				debugging.  Later, we might want to
				implement the possibility to relocate
				BLOB pages.  Then, we would need to be
				able to adjust the BLOB pointer in the
				record.  We do not store the heap
				number of the record, because it can
				change in page_zip_reorganize() or
				btr_page_reorganize().  However, also
				the page number of the record may
				change when B-tree nodes are split or
				merged. */
				mlog_write_ulint(page
						 + FIL_PAGE_FILE_FLUSH_LSN,
						 space_id,
						 MLOG_4BYTES, &mtr);
				mlog_write_ulint(page
						 + FIL_PAGE_FILE_FLUSH_LSN + 4,
						 rec_page_no,
						 MLOG_4BYTES, &mtr);

				/* Zero out the unused part of the page. */
				memset(page + page_zip_get_size(page_zip)
				       - c_stream.avail_out,
				       0, c_stream.avail_out);
				mlog_log_string(page + FIL_PAGE_FILE_FLUSH_LSN,
						page_zip_get_size(page_zip)
						- FIL_PAGE_FILE_FLUSH_LSN,
						&mtr);
				/* Copy the page to compressed storage,
				because it will be flushed to disk
				from there. */
				blob_page_zip = buf_block_get_page_zip(block);
				ut_ad(blob_page_zip);
				ut_ad(page_zip_get_size(blob_page_zip)
				      == page_zip_get_size(page_zip));
				memcpy(blob_page_zip->data, page,
				       page_zip_get_size(page_zip));

				if (err == Z_OK && prev_page_no != FIL_NULL) {

					goto next_zip_page;
				}

				if (alloc_mtr == &mtr) {
					rec_block = buf_page_get(
						space_id, zip_size,
						rec_page_no,
						RW_X_LATCH, &mtr);
					buf_block_dbg_add_level(
						rec_block,
						SYNC_NO_ORDER_CHECK);
				}

				if (err == Z_STREAM_END) {
					mach_write_to_4(field_ref
							+ BTR_EXTERN_LEN, 0);
					mach_write_to_4(field_ref
							+ BTR_EXTERN_LEN + 4,
							c_stream.total_in);
				} else {
					memset(field_ref + BTR_EXTERN_LEN,
					       0, 8);
				}

				if (prev_page_no == FIL_NULL) {
					btr_blob_dbg_add_blob(
						rec, big_rec_vec->fields[i]
						.field_no, page_no, index,
						"store");

					mach_write_to_4(field_ref
							+ BTR_EXTERN_SPACE_ID,
							space_id);

					mach_write_to_4(field_ref
							+ BTR_EXTERN_PAGE_NO,
							page_no);

					mach_write_to_4(field_ref
							+ BTR_EXTERN_OFFSET,
							FIL_PAGE_NEXT);
				}

				page_zip_write_blob_ptr(
					page_zip, rec, index, offsets,
					big_rec_vec->fields[i].field_no,
					alloc_mtr);

next_zip_page:
				prev_page_no = page_no;

				/* Commit mtr and release the
				uncompressed page frame to save memory. */
				btr_blob_free(block, FALSE, &mtr);

				if (err == Z_STREAM_END) {
					break;
				}
			} else {
				mlog_write_ulint(page + FIL_PAGE_TYPE,
						 FIL_PAGE_TYPE_BLOB,
						 MLOG_2BYTES, &mtr);

				if (extern_len > (UNIV_PAGE_SIZE
						  - FIL_PAGE_DATA
						  - BTR_BLOB_HDR_SIZE
						  - FIL_PAGE_DATA_END)) {
					store_len = UNIV_PAGE_SIZE
						- FIL_PAGE_DATA
						- BTR_BLOB_HDR_SIZE
						- FIL_PAGE_DATA_END;
				} else {
					store_len = extern_len;
				}

				mlog_write_string(page + FIL_PAGE_DATA
						  + BTR_BLOB_HDR_SIZE,
						  (const byte*)
						  big_rec_vec->fields[i].data
						  + big_rec_vec->fields[i].len
						  - extern_len,
						  store_len, &mtr);
				mlog_write_ulint(page + FIL_PAGE_DATA
						 + BTR_BLOB_HDR_PART_LEN,
						 store_len, MLOG_4BYTES, &mtr);
				mlog_write_ulint(page + FIL_PAGE_DATA
						 + BTR_BLOB_HDR_NEXT_PAGE_NO,
						 FIL_NULL, MLOG_4BYTES, &mtr);

				extern_len -= store_len;

				if (alloc_mtr == &mtr) {
					rec_block = buf_page_get(
						space_id, zip_size,
						rec_page_no,
						RW_X_LATCH, &mtr);
					buf_block_dbg_add_level(
						rec_block,
						SYNC_NO_ORDER_CHECK);
				}

				mlog_write_ulint(field_ref + BTR_EXTERN_LEN, 0,
						 MLOG_4BYTES, alloc_mtr);
				mlog_write_ulint(field_ref
						 + BTR_EXTERN_LEN + 4,
						 big_rec_vec->fields[i].len
						 - extern_len,
						 MLOG_4BYTES, alloc_mtr);

				if (prev_page_no == FIL_NULL) {
					btr_blob_dbg_add_blob(
						rec, big_rec_vec->fields[i]
						.field_no, page_no, index,
						"store");

					mlog_write_ulint(field_ref
							 + BTR_EXTERN_SPACE_ID,
							 space_id, MLOG_4BYTES,
							 alloc_mtr);

					mlog_write_ulint(field_ref
							 + BTR_EXTERN_PAGE_NO,
							 page_no, MLOG_4BYTES,
							 alloc_mtr);

					mlog_write_ulint(field_ref
							 + BTR_EXTERN_OFFSET,
							 FIL_PAGE_DATA,
							 MLOG_4BYTES,
							 alloc_mtr);
				}

				prev_page_no = page_no;

				mtr_commit(&mtr);

				if (extern_len == 0) {
					break;
				}
			}
		}
	}

func_exit:
	if (page_zip) {
		deflateEnd(&c_stream);
	}

	if (n_freed_pages) {
		ulint	i;

		ut_ad(alloc_mtr == btr_mtr);
		ut_ad(btr_blob_op_is_update(op));

		for (i = 0; i < n_freed_pages; i++) {
			btr_page_free_low(index, freed_pages[i], 0, alloc_mtr);
		}
	}

	if (heap != NULL) {
		mem_heap_free(heap);
	}

#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
	/* All pointers to externally stored columns in the record
	must be valid. */
	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
		if (!rec_offs_nth_extern(offsets, i)) {
			continue;
		}

		field_ref = btr_rec_get_field_ref(rec, offsets, i);

		/* The pointer must not be zero. */
		ut_a(0 != memcmp(field_ref, field_ref_zero,
				 BTR_EXTERN_FIELD_REF_SIZE));
		/* The column must not be disowned by this record. */
		ut_a(!(field_ref[BTR_EXTERN_LEN] & BTR_EXTERN_OWNER_FLAG));
	}
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
	return(error);
}

/*******************************************************************//**
Check the FIL_PAGE_TYPE on an uncompressed BLOB page. */
static
void
btr_check_blob_fil_page_type(
/*=========================*/
	ulint		space_id,	/*!< in: space id */
	ulint		page_no,	/*!< in: page number */
	const page_t*	page,		/*!< in: page */
	ibool		read)		/*!< in: TRUE=read, FALSE=purge */
{
	ulint	type = fil_page_get_type(page);

	ut_a(space_id == page_get_space_id(page));
	ut_a(page_no == page_get_page_no(page));

	if (UNIV_UNLIKELY(type != FIL_PAGE_TYPE_BLOB)) {
		ulint	flags = fil_space_get_flags(space_id);

#ifndef UNIV_DEBUG /* Improve debug test coverage */
		if (UNIV_LIKELY
		    ((flags & DICT_TF_FORMAT_MASK) == DICT_TF_FORMAT_51)) {
			/* Old versions of InnoDB did not initialize
			FIL_PAGE_TYPE on BLOB pages.  Do not print
			anything about the type mismatch when reading
			a BLOB page that is in Antelope format.*/
			return;
		}
#endif /* !UNIV_DEBUG */

		ut_print_timestamp(stderr);
		fprintf(stderr,
			"  InnoDB: FIL_PAGE_TYPE=%lu"
			" on BLOB %s space %lu page %lu flags %lx\n",
			(ulong) type, read ? "read" : "purge",
			(ulong) space_id, (ulong) page_no, (ulong) flags);
		ut_error;
	}
}

/*******************************************************************//**
Frees the space in an externally stored field to the file space
management if the field in data is owned by the externally stored field,
in a rollback we may have the additional condition that the field must
not be inherited. */
UNIV_INTERN
void
btr_free_externally_stored_field(
/*=============================*/
	dict_index_t*	index,		/*!< in: index of the data, the index
					tree MUST be X-latched; if the tree
					height is 1, then also the root page
					must be X-latched! (this is relevant
					in the case this function is called
					from purge where 'data' is located on
					an undo log page, not an index
					page) */
	byte*		field_ref,	/*!< in/out: field reference */
	const rec_t*	rec,		/*!< in: record containing field_ref, for
					page_zip_write_blob_ptr(), or NULL */
	const ulint*	offsets,	/*!< in: rec_get_offsets(rec, index),
					or NULL */
	page_zip_des_t*	page_zip,	/*!< in: compressed page corresponding
					to rec, or NULL if rec == NULL */
	ulint		i,		/*!< in: field number of field_ref;
					ignored if rec == NULL */
	enum trx_rb_ctx	rb_ctx,		/*!< in: rollback context */
	mtr_t*		local_mtr __attribute__((unused))) /*!< in: mtr
					containing the latch to data an an
					X-latch to the index tree */
{
	page_t*		page;
	ulint		space_id;
	ulint		rec_zip_size = dict_table_zip_size(index->table);
	ulint		ext_zip_size;
	ulint		page_no;
	ulint		next_page_no;
	mtr_t		mtr;

	ut_ad(mtr_memo_contains(local_mtr, dict_index_get_lock(index),
				MTR_MEMO_X_LOCK));
	ut_ad(mtr_memo_contains_page(local_mtr, field_ref,
				     MTR_MEMO_PAGE_X_FIX));
	ut_ad(!rec || rec_offs_validate(rec, index, offsets));
	ut_ad(!rec || field_ref == btr_rec_get_field_ref(rec, offsets, i));

	if (UNIV_UNLIKELY(!memcmp(field_ref, field_ref_zero,
				  BTR_EXTERN_FIELD_REF_SIZE))) {
		/* In the rollback of uncommitted transactions, we may
		encounter a clustered index record whose BLOBs have
		not been written.  There is nothing to free then. */
		ut_a(rb_ctx == RB_RECOVERY || rb_ctx == RB_RECOVERY_PURGE_REC);
		return;
	}

	space_id = mach_read_from_4(field_ref + BTR_EXTERN_SPACE_ID);

	if (UNIV_UNLIKELY(space_id != dict_index_get_space(index))) {
		ext_zip_size = fil_space_get_zip_size(space_id);
		/* This must be an undo log record in the system tablespace,
		that is, in row_purge_upd_exist_or_extern().
		Currently, externally stored records are stored in the
		same tablespace as the referring records. */
		ut_ad(!page_get_space_id(page_align(field_ref)));
		ut_ad(!rec);
		ut_ad(!page_zip);
	} else {
		ext_zip_size = rec_zip_size;
	}

	if (!rec) {
		/* This is a call from row_purge_upd_exist_or_extern(). */
		ut_ad(!page_zip);
		rec_zip_size = 0;
	}

#ifdef UNIV_BLOB_DEBUG
	if (!(field_ref[BTR_EXTERN_LEN] & BTR_EXTERN_OWNER_FLAG)
	    && !((field_ref[BTR_EXTERN_LEN] & BTR_EXTERN_INHERITED_FLAG)
		 && (rb_ctx == RB_NORMAL || rb_ctx == RB_RECOVERY))) {
		/* This off-page column will be freed.
		Check that no references remain. */

		btr_blob_dbg_t	b;

		b.blob_page_no = mach_read_from_4(
			field_ref + BTR_EXTERN_PAGE_NO);

		if (rec) {
			/* Remove the reference from the record to the
			BLOB. If the BLOB were not freed, the
			reference would be removed when the record is
			removed. Freeing the BLOB will overwrite the
			BTR_EXTERN_PAGE_NO in the field_ref of the
			record with FIL_NULL, which would make the
			btr_blob_dbg information inconsistent with the
			record. */
			b.ref_page_no = page_get_page_no(page_align(rec));
			b.ref_heap_no = page_rec_get_heap_no(rec);
			b.ref_field_no = i;
			btr_blob_dbg_rbt_delete(index, &b, "free");
		}

		btr_blob_dbg_assert_empty(index, b.blob_page_no);
	}
#endif /* UNIV_BLOB_DEBUG */

	for (;;) {
#ifdef UNIV_SYNC_DEBUG
		buf_block_t*	rec_block;
#endif /* UNIV_SYNC_DEBUG */
		buf_block_t*	ext_block;

		mtr_start(&mtr);

#ifdef UNIV_SYNC_DEBUG
		rec_block =
#endif /* UNIV_SYNC_DEBUG */
		buf_page_get(page_get_space_id(page_align(field_ref)),
			     rec_zip_size,
			     page_get_page_no(page_align(field_ref)),
			     RW_X_LATCH, &mtr);
		buf_block_dbg_add_level(rec_block, SYNC_NO_ORDER_CHECK);
		page_no = mach_read_from_4(field_ref + BTR_EXTERN_PAGE_NO);

		if (/* There is no external storage data */
		    page_no == FIL_NULL
		    /* This field does not own the externally stored field */
		    || (mach_read_from_1(field_ref + BTR_EXTERN_LEN)
			& BTR_EXTERN_OWNER_FLAG)
		    /* Rollback and inherited field */
		    || ((rb_ctx == RB_NORMAL || rb_ctx == RB_RECOVERY)
			&& (mach_read_from_1(field_ref + BTR_EXTERN_LEN)
			    & BTR_EXTERN_INHERITED_FLAG))) {

			/* Do not free */
			mtr_commit(&mtr);

			return;
		}

		ext_block = buf_page_get(space_id, ext_zip_size, page_no,
					 RW_X_LATCH, &mtr);
		buf_block_dbg_add_level(ext_block, SYNC_EXTERN_STORAGE);
		page = buf_block_get_frame(ext_block);

		if (ext_zip_size) {
			/* Note that page_zip will be NULL
			in row_purge_upd_exist_or_extern(). */
			switch (fil_page_get_type(page)) {
			case FIL_PAGE_TYPE_ZBLOB:
			case FIL_PAGE_TYPE_ZBLOB2:
				break;
			default:
				ut_error;
			}
			next_page_no = mach_read_from_4(page + FIL_PAGE_NEXT);

			btr_page_free_low(index, ext_block, 0, &mtr);

			if (page_zip) {
				mach_write_to_4(field_ref + BTR_EXTERN_PAGE_NO,
						next_page_no);
				mach_write_to_4(field_ref + BTR_EXTERN_LEN + 4,
						0);
				page_zip_write_blob_ptr(page_zip, rec, index,
							offsets, i, &mtr);
			} else {
				mlog_write_ulint(field_ref
						 + BTR_EXTERN_PAGE_NO,
						 next_page_no,
						 MLOG_4BYTES, &mtr);
				mlog_write_ulint(field_ref
						 + BTR_EXTERN_LEN + 4, 0,
						 MLOG_4BYTES, &mtr);
			}
		} else {
			ut_a(!page_zip);
			btr_check_blob_fil_page_type(space_id, page_no, page,
						     FALSE);

			next_page_no = mach_read_from_4(
				page + FIL_PAGE_DATA
				+ BTR_BLOB_HDR_NEXT_PAGE_NO);

			/* We must supply the page level (= 0) as an argument
			because we did not store it on the page (we save the
			space overhead from an index page header. */

			btr_page_free_low(index, ext_block, 0, &mtr);

			mlog_write_ulint(field_ref + BTR_EXTERN_PAGE_NO,
					 next_page_no,
					 MLOG_4BYTES, &mtr);
			/* Zero out the BLOB length.  If the server
			crashes during the execution of this function,
			trx_rollback_or_clean_all_recovered() could
			dereference the half-deleted BLOB, fetching a
			wrong prefix for the BLOB. */
			mlog_write_ulint(field_ref + BTR_EXTERN_LEN + 4,
					 0,
					 MLOG_4BYTES, &mtr);
		}

		/* Commit mtr and release the BLOB block to save memory. */
		btr_blob_free(ext_block, TRUE, &mtr);
	}
}

/***********************************************************//**
Frees the externally stored fields for a record. */
static
void
btr_rec_free_externally_stored_fields(
/*==================================*/
	dict_index_t*	index,	/*!< in: index of the data, the index
				tree MUST be X-latched */
	rec_t*		rec,	/*!< in/out: record */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec, index) */
	page_zip_des_t*	page_zip,/*!< in: compressed page whose uncompressed
				part will be updated, or NULL */
	enum trx_rb_ctx	rb_ctx,	/*!< in: rollback context */
	mtr_t*		mtr)	/*!< in: mini-transaction handle which contains
				an X-latch to record page and to the index
				tree */
{
	ulint	n_fields;
	ulint	i;

	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX));
	/* Free possible externally stored fields in the record */

	ut_ad(dict_table_is_comp(index->table) == !!rec_offs_comp(offsets));
	n_fields = rec_offs_n_fields(offsets);

	for (i = 0; i < n_fields; i++) {
		if (rec_offs_nth_extern(offsets, i)) {
			btr_free_externally_stored_field(
				index, btr_rec_get_field_ref(rec, offsets, i),
				rec, offsets, page_zip, i, rb_ctx, mtr);
		}
	}
}

/***********************************************************//**
Frees the externally stored fields for a record, if the field is mentioned
in the update vector. */
static
void
btr_rec_free_updated_extern_fields(
/*===============================*/
	dict_index_t*	index,	/*!< in: index of rec; the index tree MUST be
				X-latched */
	rec_t*		rec,	/*!< in/out: record */
	page_zip_des_t*	page_zip,/*!< in: compressed page whose uncompressed
				part will be updated, or NULL */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec, index) */
	const upd_t*	update,	/*!< in: update vector */
	enum trx_rb_ctx	rb_ctx,	/*!< in: rollback context */
	mtr_t*		mtr)	/*!< in: mini-transaction handle which contains
				an X-latch to record page and to the tree */
{
	ulint	n_fields;
	ulint	i;

	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX));

	/* Free possible externally stored fields in the record */

	n_fields = upd_get_n_fields(update);

	for (i = 0; i < n_fields; i++) {
		const upd_field_t* ufield = upd_get_nth_field(update, i);

		if (rec_offs_nth_extern(offsets, ufield->field_no)) {
			ulint	len;
			byte*	data = rec_get_nth_field(
				rec, offsets, ufield->field_no, &len);
			ut_a(len >= BTR_EXTERN_FIELD_REF_SIZE);

			btr_free_externally_stored_field(
				index, data + len - BTR_EXTERN_FIELD_REF_SIZE,
				rec, offsets, page_zip,
				ufield->field_no, rb_ctx, mtr);
		}
	}
}

/*******************************************************************//**
Copies the prefix of an uncompressed BLOB.  The clustered index record
that points to this BLOB must be protected by a lock or a page latch.
@return	number of bytes written to buf */
static
ulint
btr_copy_blob_prefix(
/*=================*/
	byte*		buf,	/*!< out: the externally stored part of
				the field, or a prefix of it */
	ulint		len,	/*!< in: length of buf, in bytes */
	ulint		space_id,/*!< in: space id of the BLOB pages */
	ulint		page_no,/*!< in: page number of the first BLOB page */
	ulint		offset)	/*!< in: offset on the first BLOB page */
{
	ulint	copied_len	= 0;

	for (;;) {
		mtr_t		mtr;
		buf_block_t*	block;
		const page_t*	page;
		const byte*	blob_header;
		ulint		part_len;
		ulint		copy_len;

		mtr_start(&mtr);

		block = buf_page_get(space_id, 0, page_no, RW_S_LATCH, &mtr);
		buf_block_dbg_add_level(block, SYNC_EXTERN_STORAGE);
		page = buf_block_get_frame(block);

		btr_check_blob_fil_page_type(space_id, page_no, page, TRUE);

		blob_header = page + offset;
		part_len = btr_blob_get_part_len(blob_header);
		copy_len = ut_min(part_len, len - copied_len);

		memcpy(buf + copied_len,
		       blob_header + BTR_BLOB_HDR_SIZE, copy_len);
		copied_len += copy_len;

		page_no = btr_blob_get_next_page_no(blob_header);

		mtr_commit(&mtr);

		if (page_no == FIL_NULL || copy_len != part_len) {
			UNIV_MEM_ASSERT_RW(buf, copied_len);
			return(copied_len);
		}

		/* On other BLOB pages except the first the BLOB header
		always is at the page data start: */

		offset = FIL_PAGE_DATA;

		ut_ad(copied_len <= len);
	}
}

/*******************************************************************//**
Copies the prefix of a compressed BLOB.  The clustered index record
that points to this BLOB must be protected by a lock or a page latch.
@return	number of bytes written to buf */
static
ulint
btr_copy_zblob_prefix(
/*==================*/
	byte*		buf,	/*!< out: the externally stored part of
				the field, or a prefix of it */
	ulint		len,	/*!< in: length of buf, in bytes */
	ulint		zip_size,/*!< in: compressed BLOB page size */
	ulint		space_id,/*!< in: space id of the BLOB pages */
	ulint		page_no,/*!< in: page number of the first BLOB page */
	ulint		offset)	/*!< in: offset on the first BLOB page */
{
	ulint		page_type = FIL_PAGE_TYPE_ZBLOB;
	mem_heap_t*	heap;
	int		err;
	z_stream	d_stream;

	d_stream.next_out = buf;
	d_stream.avail_out = len;
	d_stream.next_in = Z_NULL;
	d_stream.avail_in = 0;

	/* Zlib inflate needs 32 kilobytes for the default
	window size, plus a few kilobytes for small objects. */
	heap = mem_heap_create(40000);
	page_zip_set_alloc(&d_stream, heap);

	ut_ad(ut_is_2pow(zip_size));
	ut_ad(zip_size >= PAGE_ZIP_MIN_SIZE);
	ut_ad(zip_size <= UNIV_PAGE_SIZE);
	ut_ad(space_id);

	err = inflateInit(&d_stream);
	ut_a(err == Z_OK);

	for (;;) {
		buf_page_t*	bpage;
		ulint		next_page_no;

		/* There is no latch on bpage directly.  Instead,
		bpage is protected by the B-tree page latch that
		is being held on the clustered index record, or,
		in row_merge_copy_blobs(), by an exclusive table lock. */
		bpage = buf_page_get_zip(space_id, zip_size, page_no);

		if (UNIV_UNLIKELY(!bpage)) {
			ut_print_timestamp(stderr);
			fprintf(stderr,
				"  InnoDB: Cannot load"
				" compressed BLOB"
				" page %lu space %lu\n",
				(ulong) page_no, (ulong) space_id);
			goto func_exit;
		}

		if (UNIV_UNLIKELY
		    (fil_page_get_type(bpage->zip.data) != page_type)) {
			ut_print_timestamp(stderr);
			fprintf(stderr,
				"  InnoDB: Unexpected type %lu of"
				" compressed BLOB"
				" page %lu space %lu\n",
				(ulong) fil_page_get_type(bpage->zip.data),
				(ulong) page_no, (ulong) space_id);
			goto end_of_blob;
		}

		next_page_no = mach_read_from_4(bpage->zip.data + offset);

		if (UNIV_LIKELY(offset == FIL_PAGE_NEXT)) {
			/* When the BLOB begins at page header,
			the compressed data payload does not
			immediately follow the next page pointer. */
			offset = FIL_PAGE_DATA;
		} else {
			offset += 4;
		}

		d_stream.next_in = bpage->zip.data + offset;
		d_stream.avail_in = zip_size - offset;

		err = inflate(&d_stream, Z_NO_FLUSH);
		switch (err) {
		case Z_OK:
			if (!d_stream.avail_out) {
				goto end_of_blob;
			}
			break;
		case Z_STREAM_END:
			if (next_page_no == FIL_NULL) {
				goto end_of_blob;
			}
			/* fall through */
		default:
inflate_error:
			ut_print_timestamp(stderr);
			fprintf(stderr,
				"  InnoDB: inflate() of"
				" compressed BLOB"
				" page %lu space %lu returned %d (%s)\n",
				(ulong) page_no, (ulong) space_id,
				err, d_stream.msg);
		case Z_BUF_ERROR:
			goto end_of_blob;
		}

		if (next_page_no == FIL_NULL) {
			if (!d_stream.avail_in) {
				ut_print_timestamp(stderr);
				fprintf(stderr,
					"  InnoDB: unexpected end of"
					" compressed BLOB"
					" page %lu space %lu\n",
					(ulong) page_no,
					(ulong) space_id);
			} else {
				err = inflate(&d_stream, Z_FINISH);
				switch (err) {
				case Z_STREAM_END:
				case Z_BUF_ERROR:
					break;
				default:
					goto inflate_error;
				}
			}

end_of_blob:
			buf_page_release_zip(bpage);
			goto func_exit;
		}

		buf_page_release_zip(bpage);

		/* On other BLOB pages except the first
		the BLOB header always is at the page header: */

		page_no = next_page_no;
		offset = FIL_PAGE_NEXT;
		page_type = FIL_PAGE_TYPE_ZBLOB2;
	}

func_exit:
	inflateEnd(&d_stream);
	mem_heap_free(heap);
	UNIV_MEM_ASSERT_RW(buf, d_stream.total_out);
	return(d_stream.total_out);
}

/*******************************************************************//**
Copies the prefix of an externally stored field of a record.  The
clustered index record that points to this BLOB must be protected by a
lock or a page latch.
@return	number of bytes written to buf */
static
ulint
btr_copy_externally_stored_field_prefix_low(
/*========================================*/
	byte*		buf,	/*!< out: the externally stored part of
				the field, or a prefix of it */
	ulint		len,	/*!< in: length of buf, in bytes */
	ulint		zip_size,/*!< in: nonzero=compressed BLOB page size,
				zero for uncompressed BLOBs */
	ulint		space_id,/*!< in: space id of the first BLOB page */
	ulint		page_no,/*!< in: page number of the first BLOB page */
	ulint		offset)	/*!< in: offset on the first BLOB page */
{
	if (UNIV_UNLIKELY(len == 0)) {
		return(0);
	}

	if (UNIV_UNLIKELY(zip_size)) {
		return(btr_copy_zblob_prefix(buf, len, zip_size,
					     space_id, page_no, offset));
	} else {
		return(btr_copy_blob_prefix(buf, len, space_id,
					    page_no, offset));
	}
}

/*******************************************************************//**
Copies the prefix of an externally stored field of a record.  The
clustered index record must be protected by a lock or a page latch.
@return the length of the copied field, or 0 if the column was being
or has been deleted */
UNIV_INTERN
ulint
btr_copy_externally_stored_field_prefix(
/*====================================*/
	byte*		buf,	/*!< out: the field, or a prefix of it */
	ulint		len,	/*!< in: length of buf, in bytes */
	ulint		zip_size,/*!< in: nonzero=compressed BLOB page size,
				zero for uncompressed BLOBs */
	const byte*	data,	/*!< in: 'internally' stored part of the
				field containing also the reference to
				the external part; must be protected by
				a lock or a page latch */
	ulint		local_len)/*!< in: length of data, in bytes */
{
	ulint	space_id;
	ulint	page_no;
	ulint	offset;

	ut_a(local_len >= BTR_EXTERN_FIELD_REF_SIZE);

	local_len -= BTR_EXTERN_FIELD_REF_SIZE;

	if (UNIV_UNLIKELY(local_len >= len)) {
		memcpy(buf, data, len);
		return(len);
	}

	memcpy(buf, data, local_len);
	data += local_len;

	ut_a(memcmp(data, field_ref_zero, BTR_EXTERN_FIELD_REF_SIZE));

	if (!mach_read_from_4(data + BTR_EXTERN_LEN + 4)) {
		/* The externally stored part of the column has been
		(partially) deleted.  Signal the half-deleted BLOB
		to the caller. */

		return(0);
	}

	space_id = mach_read_from_4(data + BTR_EXTERN_SPACE_ID);

	page_no = mach_read_from_4(data + BTR_EXTERN_PAGE_NO);

	offset = mach_read_from_4(data + BTR_EXTERN_OFFSET);

	return(local_len
	       + btr_copy_externally_stored_field_prefix_low(buf + local_len,
							     len - local_len,
							     zip_size,
							     space_id, page_no,
							     offset));
}

/*******************************************************************//**
Copies an externally stored field of a record to mem heap.  The
clustered index record must be protected by a lock or a page latch.
@return	the whole field copied to heap */
static
byte*
btr_copy_externally_stored_field(
/*=============================*/
	ulint*		len,	/*!< out: length of the whole field */
	const byte*	data,	/*!< in: 'internally' stored part of the
				field containing also the reference to
				the external part; must be protected by
				a lock or a page latch */
	ulint		zip_size,/*!< in: nonzero=compressed BLOB page size,
				zero for uncompressed BLOBs */
	ulint		local_len,/*!< in: length of data */
	mem_heap_t*	heap)	/*!< in: mem heap */
{
	ulint	space_id;
	ulint	page_no;
	ulint	offset;
	ulint	extern_len;
	byte*	buf;

	ut_a(local_len >= BTR_EXTERN_FIELD_REF_SIZE);

	local_len -= BTR_EXTERN_FIELD_REF_SIZE;

	space_id = mach_read_from_4(data + local_len + BTR_EXTERN_SPACE_ID);

	page_no = mach_read_from_4(data + local_len + BTR_EXTERN_PAGE_NO);

	offset = mach_read_from_4(data + local_len + BTR_EXTERN_OFFSET);

	/* Currently a BLOB cannot be bigger than 4 GB; we
	leave the 4 upper bytes in the length field unused */

	extern_len = mach_read_from_4(data + local_len + BTR_EXTERN_LEN + 4);

	buf = mem_heap_alloc(heap, local_len + extern_len);

	memcpy(buf, data, local_len);
	*len = local_len
		+ btr_copy_externally_stored_field_prefix_low(buf + local_len,
							      extern_len,
							      zip_size,
							      space_id,
							      page_no, offset);

	return(buf);
}

/*******************************************************************//**
Copies an externally stored field of a record to mem heap.
@return	the field copied to heap, or NULL if the field is incomplete */
UNIV_INTERN
byte*
btr_rec_copy_externally_stored_field(
/*=================================*/
	const rec_t*	rec,	/*!< in: record in a clustered index;
				must be protected by a lock or a page latch */
	const ulint*	offsets,/*!< in: array returned by rec_get_offsets() */
	ulint		zip_size,/*!< in: nonzero=compressed BLOB page size,
				zero for uncompressed BLOBs */
	ulint		no,	/*!< in: field number */
	ulint*		len,	/*!< out: length of the field */
	mem_heap_t*	heap)	/*!< in: mem heap */
{
	ulint		local_len;
	const byte*	data;

	ut_a(rec_offs_nth_extern(offsets, no));

	/* An externally stored field can contain some initial
	data from the field, and in the last 20 bytes it has the
	space id, page number, and offset where the rest of the
	field data is stored, and the data length in addition to
	the data stored locally. We may need to store some data
	locally to get the local record length above the 128 byte
	limit so that field offsets are stored in two bytes, and
	the extern bit is available in those two bytes. */

	data = rec_get_nth_field(rec, offsets, no, &local_len);

	ut_a(local_len >= BTR_EXTERN_FIELD_REF_SIZE);

	if (UNIV_UNLIKELY
	    (!memcmp(data + local_len - BTR_EXTERN_FIELD_REF_SIZE,
		     field_ref_zero, BTR_EXTERN_FIELD_REF_SIZE))) {
		/* The externally stored field was not written yet.
		This record should only be seen by
		recv_recovery_rollback_active() or any
		TRX_ISO_READ_UNCOMMITTED transactions. */
		return(NULL);
	}

	return(btr_copy_externally_stored_field(len, data,
						zip_size, local_len, heap));
}
#endif /* !UNIV_HOTBACKUP */