mariadb/include/page0page.ic

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

Copyright (c) 1994, 2009, Innobase Oy. All Rights Reserved.

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., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

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

/******************************************************
Index page routines

Created 2/2/1994 Heikki Tuuri
*******************************************************/

#include "mach0data.h"
#ifdef UNIV_DEBUG
# include "log0recv.h"
#endif /* !UNIV_DEBUG */
#ifndef UNIV_HOTBACKUP
# include "rem0cmp.h"
#endif /* !UNIV_HOTBACKUP */
#include "mtr0log.h"
#include "page0zip.h"

#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE
#endif

/****************************************************************
Gets the start of a page. */
UNIV_INLINE
page_t*
page_align(
/*=======*/
				/* out: start of the page */
	const void*	ptr)	/* in: pointer to page frame */
{
	return((page_t*) ut_align_down(ptr, UNIV_PAGE_SIZE));
}
/****************************************************************
Gets the offset within a page. */
UNIV_INLINE
ulint
page_offset(
/*========*/
				/* out: offset from the start of the page */
	const void*	ptr)	/* in: pointer to page frame */
{
	return(ut_align_offset(ptr, UNIV_PAGE_SIZE));
}
/*****************************************************************
Returns the max trx id field value. */
UNIV_INLINE
trx_id_t
page_get_max_trx_id(
/*================*/
	const page_t*	page)	/* in: page */
{
	ut_ad(page);

	return(mach_read_from_8(page + PAGE_HEADER + PAGE_MAX_TRX_ID));
}

/*****************************************************************
Sets the max trx id field value if trx_id is bigger than the previous
value. */
UNIV_INLINE
void
page_update_max_trx_id(
/*===================*/
	buf_block_t*	block,	/* in/out: page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	trx_id_t	trx_id,	/* in: transaction id */
	mtr_t*		mtr)	/* in/out: mini-transaction */
{
	ut_ad(block);
	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	/* During crash recovery, this function may be called on
	something else than a leaf page of a secondary index or the
	insert buffer index tree (dict_index_is_sec_or_ibuf() returns
	TRUE for the dummy indexes constructed during redo log
	application).  In that case, PAGE_MAX_TRX_ID is unused,
	and trx_id is usually zero. */
	ut_ad(!ut_dulint_is_zero(trx_id) || recv_recovery_is_on());
	ut_ad(page_is_leaf(buf_block_get_frame(block)));

	if (ut_dulint_cmp(page_get_max_trx_id(buf_block_get_frame(block)),
			  trx_id) < 0) {

		page_set_max_trx_id(block, page_zip, trx_id, mtr);
	}
}

/*****************************************************************
Reads the given header field. */
UNIV_INLINE
ulint
page_header_get_field(
/*==================*/
	const page_t*	page,	/* in: page */
	ulint		field)	/* in: PAGE_LEVEL, ... */
{
	ut_ad(page);
	ut_ad(field <= PAGE_INDEX_ID);

	return(mach_read_from_2(page + PAGE_HEADER + field));
}

/*****************************************************************
Sets the given header field. */
UNIV_INLINE
void
page_header_set_field(
/*==================*/
	page_t*		page,	/* in/out: page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		field,	/* in: PAGE_N_DIR_SLOTS, ... */
	ulint		val)	/* in: value */
{
	ut_ad(page);
	ut_ad(field <= PAGE_N_RECS);
	ut_ad(field == PAGE_N_HEAP || val < UNIV_PAGE_SIZE);
	ut_ad(field != PAGE_N_HEAP || (val & 0x7fff) < UNIV_PAGE_SIZE);

	mach_write_to_2(page + PAGE_HEADER + field, val);
	if (UNIV_LIKELY_NULL(page_zip)) {
		page_zip_write_header(page_zip,
				      page + PAGE_HEADER + field, 2, NULL);
	}
}

/*****************************************************************
Returns the offset stored in the given header field. */
UNIV_INLINE
ulint
page_header_get_offs(
/*=================*/
				/* out: offset from the start of the page,
				or 0 */
	const page_t*	page,	/* in: page */
	ulint		field)	/* in: PAGE_FREE, ... */
{
	ulint	offs;

	ut_ad(page);
	ut_ad((field == PAGE_FREE)
	      || (field == PAGE_LAST_INSERT)
	      || (field == PAGE_HEAP_TOP));

	offs = page_header_get_field(page, field);

	ut_ad((field != PAGE_HEAP_TOP) || offs);

	return(offs);
}

/*****************************************************************
Sets the pointer stored in the given header field. */
UNIV_INLINE
void
page_header_set_ptr(
/*================*/
	page_t*		page,	/* in: page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		field,	/* in: PAGE_FREE, ... */
	const byte*	ptr)	/* in: pointer or NULL*/
{
	ulint	offs;

	ut_ad(page);
	ut_ad((field == PAGE_FREE)
	      || (field == PAGE_LAST_INSERT)
	      || (field == PAGE_HEAP_TOP));

	if (ptr == NULL) {
		offs = 0;
	} else {
		offs = ptr - page;
	}

	ut_ad((field != PAGE_HEAP_TOP) || offs);

	page_header_set_field(page, page_zip, field, offs);
}

#ifndef UNIV_HOTBACKUP
/*****************************************************************
Resets the last insert info field in the page header. Writes to mlog
about this operation. */
UNIV_INLINE
void
page_header_reset_last_insert(
/*==========================*/
	page_t*		page,	/* in/out: page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	mtr_t*		mtr)	/* in: mtr */
{
	ut_ad(page && mtr);

	if (UNIV_LIKELY_NULL(page_zip)) {
		mach_write_to_2(page + (PAGE_HEADER + PAGE_LAST_INSERT), 0);
		page_zip_write_header(page_zip,
				      page + (PAGE_HEADER + PAGE_LAST_INSERT),
				      2, mtr);
	} else {
		mlog_write_ulint(page + (PAGE_HEADER + PAGE_LAST_INSERT), 0,
				 MLOG_2BYTES, mtr);
	}
}
#endif /* !UNIV_HOTBACKUP */

/****************************************************************
Determine whether the page is in new-style compact format. */
UNIV_INLINE
ulint
page_is_comp(
/*=========*/
				/* out: nonzero if the page is in compact
				format, zero if it is in old-style format */
	const page_t*	page)	/* in: index page */
{
	return(UNIV_EXPECT(page_header_get_field(page, PAGE_N_HEAP) & 0x8000,
			   0x8000));
}

/****************************************************************
TRUE if the record is on a page in compact format. */
UNIV_INLINE
ulint
page_rec_is_comp(
/*=============*/
				/* out: nonzero if in compact format */
	const rec_t*	rec)	/* in: record */
{
	return(page_is_comp(page_align(rec)));
}

/*******************************************************************
Returns the heap number of a record. */
UNIV_INLINE
ulint
page_rec_get_heap_no(
/*=================*/
				/* out: heap number */
	const rec_t*	rec)	/* in: the physical record */
{
	if (page_rec_is_comp(rec)) {
		return(rec_get_heap_no_new(rec));
	} else {
		return(rec_get_heap_no_old(rec));
	}
}

/****************************************************************
Determine whether the page is a B-tree leaf. */
UNIV_INLINE
ibool
page_is_leaf(
/*=========*/
				/* out: TRUE if the page is a B-tree leaf */
	const page_t*	page)	/* in: page */
{
	return(!*(const uint16*) (page + (PAGE_HEADER + PAGE_LEVEL)));
}

/****************************************************************
Gets the offset of the first record on the page. */
UNIV_INLINE
ulint
page_get_infimum_offset(
/*====================*/
				/* out: offset of the first record
				in record list, relative from page */
	const page_t*	page)	/* in: page which must have record(s) */
{
	ut_ad(page);
	ut_ad(!page_offset(page));

	if (page_is_comp(page)) {
		return(PAGE_NEW_INFIMUM);
	} else {
		return(PAGE_OLD_INFIMUM);
	}
}

/****************************************************************
Gets the offset of the last record on the page. */
UNIV_INLINE
ulint
page_get_supremum_offset(
/*=====================*/
				/* out: offset of the last record in
				record list, relative from page */
	const page_t*	page)	/* in: page which must have record(s) */
{
	ut_ad(page);
	ut_ad(!page_offset(page));

	if (page_is_comp(page)) {
		return(PAGE_NEW_SUPREMUM);
	} else {
		return(PAGE_OLD_SUPREMUM);
	}
}

/****************************************************************
TRUE if the record is a user record on the page. */
UNIV_INLINE
ibool
page_rec_is_user_rec_low(
/*=====================*/
			/* out: TRUE if a user record */
	ulint	offset)	/* in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
#if PAGE_OLD_INFIMUM < PAGE_NEW_INFIMUM
# error "PAGE_OLD_INFIMUM < PAGE_NEW_INFIMUM"
#endif
#if PAGE_OLD_SUPREMUM < PAGE_NEW_SUPREMUM
# error "PAGE_OLD_SUPREMUM < PAGE_NEW_SUPREMUM"
#endif
#if PAGE_NEW_INFIMUM > PAGE_OLD_SUPREMUM
# error "PAGE_NEW_INFIMUM > PAGE_OLD_SUPREMUM"
#endif
#if PAGE_OLD_INFIMUM > PAGE_NEW_SUPREMUM
# error "PAGE_OLD_INFIMUM > PAGE_NEW_SUPREMUM"
#endif
#if PAGE_NEW_SUPREMUM > PAGE_OLD_SUPREMUM_END
# error "PAGE_NEW_SUPREMUM > PAGE_OLD_SUPREMUM_END"
#endif
#if PAGE_OLD_SUPREMUM > PAGE_NEW_SUPREMUM_END
# error "PAGE_OLD_SUPREMUM > PAGE_NEW_SUPREMUM_END"
#endif
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(UNIV_LIKELY(offset != PAGE_NEW_SUPREMUM)
	       && UNIV_LIKELY(offset != PAGE_NEW_INFIMUM)
	       && UNIV_LIKELY(offset != PAGE_OLD_INFIMUM)
	       && UNIV_LIKELY(offset != PAGE_OLD_SUPREMUM));
}

/****************************************************************
TRUE if the record is the supremum record on a page. */
UNIV_INLINE
ibool
page_rec_is_supremum_low(
/*=====================*/
			/* out: TRUE if the supremum record */
	ulint	offset)	/* in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(UNIV_UNLIKELY(offset == PAGE_NEW_SUPREMUM)
	       || UNIV_UNLIKELY(offset == PAGE_OLD_SUPREMUM));
}

/****************************************************************
TRUE if the record is the infimum record on a page. */
UNIV_INLINE
ibool
page_rec_is_infimum_low(
/*====================*/
			/* out: TRUE if the infimum record */
	ulint	offset)	/* in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(UNIV_UNLIKELY(offset == PAGE_NEW_INFIMUM)
	       || UNIV_UNLIKELY(offset == PAGE_OLD_INFIMUM));
}

/****************************************************************
TRUE if the record is a user record on the page. */
UNIV_INLINE
ibool
page_rec_is_user_rec(
/*=================*/
				/* out: TRUE if a user record */
	const rec_t*	rec)	/* in: record */
{
	return(page_rec_is_user_rec_low(page_offset(rec)));
}

/****************************************************************
TRUE if the record is the supremum record on a page. */
UNIV_INLINE
ibool
page_rec_is_supremum(
/*=================*/
				/* out: TRUE if the supremum record */
	const rec_t*	rec)	/* in: record */
{
	return(page_rec_is_supremum_low(page_offset(rec)));
}

/****************************************************************
TRUE if the record is the infimum record on a page. */
UNIV_INLINE
ibool
page_rec_is_infimum(
/*================*/
				/* out: TRUE if the infimum record */
	const rec_t*	rec)	/* in: record */
{
	return(page_rec_is_infimum_low(page_offset(rec)));
}

#ifndef UNIV_HOTBACKUP
/*****************************************************************
Compares a data tuple to a physical record. Differs from the function
cmp_dtuple_rec_with_match in the way that the record must reside on an
index page, and also page infimum and supremum records can be given in
the parameter rec. These are considered as the negative infinity and
the positive infinity in the alphabetical order. */
UNIV_INLINE
int
page_cmp_dtuple_rec_with_match(
/*===========================*/
				/* out: 1, 0, -1, if dtuple is greater, equal,
				less than rec, respectively, when only the
				common first fields are compared */
	const dtuple_t*	dtuple,	/* in: data tuple */
	const rec_t*	rec,	/* in: physical record on a page; may also
				be page infimum or supremum, in which case
				matched-parameter values below are not
				affected */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint*		matched_fields, /* in/out: number of already completely
				matched fields; when function returns
				contains the value for current comparison */
	ulint*		matched_bytes) /* in/out: number of already matched
				bytes within the first field not completely
				matched; when function returns contains the
				value for current comparison */
{
	ulint	rec_offset;

	ut_ad(dtuple_check_typed(dtuple));
	ut_ad(rec_offs_validate(rec, NULL, offsets));
	ut_ad(!rec_offs_comp(offsets) == !page_rec_is_comp(rec));

	rec_offset = page_offset(rec);

	if (UNIV_UNLIKELY(rec_offset == PAGE_NEW_INFIMUM)
	    || UNIV_UNLIKELY(rec_offset == PAGE_OLD_INFIMUM)) {
		return(1);
	}
	if (UNIV_UNLIKELY(rec_offset == PAGE_NEW_SUPREMUM)
	    || UNIV_UNLIKELY(rec_offset == PAGE_OLD_SUPREMUM)) {
		return(-1);
	}

	return(cmp_dtuple_rec_with_match(dtuple, rec, offsets,
					 matched_fields,
					 matched_bytes));
}
#endif /* !UNIV_HOTBACKUP */

/*****************************************************************
Gets the page number. */
UNIV_INLINE
ulint
page_get_page_no(
/*=============*/
				/* out: page number */
	const page_t*	page)	/* in: page */
{
	ut_ad(page == page_align((page_t*) page));
	return(mach_read_from_4(page + FIL_PAGE_OFFSET));
}

/*****************************************************************
Gets the tablespace identifier. */
UNIV_INLINE
ulint
page_get_space_id(
/*==============*/
				/* out: space id */
	const page_t*	page)	/* in: page */
{
	ut_ad(page == page_align((page_t*) page));
	return(mach_read_from_4(page + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID));
}

/*****************************************************************
Gets the number of user records on page (infimum and supremum records
are not user records). */
UNIV_INLINE
ulint
page_get_n_recs(
/*============*/
				/* out: number of user records */
	const page_t*	page)	/* in: index page */
{
	return(page_header_get_field(page, PAGE_N_RECS));
}

/*****************************************************************
Gets the number of dir slots in directory. */
UNIV_INLINE
ulint
page_dir_get_n_slots(
/*=================*/
				/* out: number of slots */
	const page_t*	page)	/* in: index page */
{
	return(page_header_get_field(page, PAGE_N_DIR_SLOTS));
}
/*****************************************************************
Sets the number of dir slots in directory. */
UNIV_INLINE
void
page_dir_set_n_slots(
/*=================*/
	page_t*		page,	/* in/out: page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		n_slots)/* in: number of slots */
{
	page_header_set_field(page, page_zip, PAGE_N_DIR_SLOTS, n_slots);
}

/*****************************************************************
Gets the number of records in the heap. */
UNIV_INLINE
ulint
page_dir_get_n_heap(
/*================*/
				/* out: number of user records */
	const page_t*	page)	/* in: index page */
{
	return(page_header_get_field(page, PAGE_N_HEAP) & 0x7fff);
}

/*****************************************************************
Sets the number of records in the heap. */
UNIV_INLINE
void
page_dir_set_n_heap(
/*================*/
	page_t*		page,	/* in/out: index page */
	page_zip_des_t*	page_zip,/* in/out: compressed page whose
				uncompressed part will be updated, or NULL.
				Note that the size of the dense page directory
				in the compressed page trailer is
				n_heap * PAGE_ZIP_DIR_SLOT_SIZE. */
	ulint		n_heap)	/* in: number of records */
{
	ut_ad(n_heap < 0x8000);
	ut_ad(!page_zip || n_heap
	      == (page_header_get_field(page, PAGE_N_HEAP) & 0x7fff) + 1);

	page_header_set_field(page, page_zip, PAGE_N_HEAP, n_heap
			      | (0x8000
				 & page_header_get_field(page, PAGE_N_HEAP)));
}

#ifdef UNIV_DEBUG
/*****************************************************************
Gets pointer to nth directory slot. */
UNIV_INLINE
page_dir_slot_t*
page_dir_get_nth_slot(
/*==================*/
				/* out: pointer to dir slot */
	const page_t*	page,	/* in: index page */
	ulint		n)	/* in: position */
{
	ut_ad(page_dir_get_n_slots(page) > n);

	return((page_dir_slot_t*)
	       page + UNIV_PAGE_SIZE - PAGE_DIR
	       - (n + 1) * PAGE_DIR_SLOT_SIZE);
}
#endif /* UNIV_DEBUG */

/******************************************************************
Used to check the consistency of a record on a page. */
UNIV_INLINE
ibool
page_rec_check(
/*===========*/
				/* out: TRUE if succeed */
	const rec_t*	rec)	/* in: record */
{
	const page_t*	page = page_align(rec);

	ut_a(rec);

	ut_a(page_offset(rec) <= page_header_get_field(page, PAGE_HEAP_TOP));
	ut_a(page_offset(rec) >= PAGE_DATA);

	return(TRUE);
}

/*******************************************************************
Gets the record pointed to by a directory slot. */
UNIV_INLINE
const rec_t*
page_dir_slot_get_rec(
/*==================*/
					/* out: pointer to record */
	const page_dir_slot_t*	slot)	/* in: directory slot */
{
	return(page_align(slot) + mach_read_from_2(slot));
}

/*******************************************************************
This is used to set the record offset in a directory slot. */
UNIV_INLINE
void
page_dir_slot_set_rec(
/*==================*/
	page_dir_slot_t* slot,	/* in: directory slot */
	rec_t*		 rec)	/* in: record on the page */
{
	ut_ad(page_rec_check(rec));

	mach_write_to_2(slot, page_offset(rec));
}

/*******************************************************************
Gets the number of records owned by a directory slot. */
UNIV_INLINE
ulint
page_dir_slot_get_n_owned(
/*======================*/
					/* out: number of records */
	const page_dir_slot_t*	slot)	/* in: page directory slot */
{
	const rec_t*	rec	= page_dir_slot_get_rec(slot);
	if (page_rec_is_comp(slot)) {
		return(rec_get_n_owned_new(rec));
	} else {
		return(rec_get_n_owned_old(rec));
	}
}

/*******************************************************************
This is used to set the owned records field of a directory slot. */
UNIV_INLINE
void
page_dir_slot_set_n_owned(
/*======================*/
	page_dir_slot_t*slot,	/* in/out: directory slot */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	ulint		n)	/* in: number of records owned by the slot */
{
	rec_t*	rec	= (rec_t*) page_dir_slot_get_rec(slot);
	if (page_rec_is_comp(slot)) {
		rec_set_n_owned_new(rec, page_zip, n);
	} else {
		ut_ad(!page_zip);
		rec_set_n_owned_old(rec, n);
	}
}

/****************************************************************
Calculates the space reserved for directory slots of a given number of
records. The exact value is a fraction number n * PAGE_DIR_SLOT_SIZE /
PAGE_DIR_SLOT_MIN_N_OWNED, and it is rounded upwards to an integer. */
UNIV_INLINE
ulint
page_dir_calc_reserved_space(
/*=========================*/
	ulint	n_recs)		/* in: number of records */
{
	return((PAGE_DIR_SLOT_SIZE * n_recs + PAGE_DIR_SLOT_MIN_N_OWNED - 1)
	       / PAGE_DIR_SLOT_MIN_N_OWNED);
}

/****************************************************************
Gets the pointer to the next record on the page. */
UNIV_INLINE
const rec_t*
page_rec_get_next_low(
/*==================*/
				/* out: pointer to next record */
	const rec_t*	rec,	/* in: pointer to record */
	ulint		comp)	/* in: nonzero=compact page layout */
{
	ulint		offs;
	const page_t*	page;

	ut_ad(page_rec_check(rec));

	page = page_align(rec);

	offs = rec_get_next_offs(rec, comp);

	if (UNIV_UNLIKELY(offs >= UNIV_PAGE_SIZE)) {
		fprintf(stderr,
			"InnoDB: Next record offset is nonsensical %lu"
			" in record at offset %lu\n"
			"InnoDB: rec address %p, space id %lu, page %lu\n",
			(ulong)offs, (ulong) page_offset(rec),
			(void*) rec,
			(ulong) page_get_space_id(page),
			(ulong) page_get_page_no(page));
		buf_page_print(page, 0);

		ut_error;
	}

	if (UNIV_UNLIKELY(offs == 0)) {

		return(NULL);
	}

	return(page + offs);
}

/****************************************************************
Gets the pointer to the next record on the page. */
UNIV_INLINE
rec_t*
page_rec_get_next(
/*==============*/
			/* out: pointer to next record */
	rec_t*	rec)	/* in: pointer to record */
{
	return((rec_t*) page_rec_get_next_low(rec, page_rec_is_comp(rec)));
}

/****************************************************************
Gets the pointer to the next record on the page. */
UNIV_INLINE
const rec_t*
page_rec_get_next_const(
/*====================*/
				/* out: pointer to next record */
	const rec_t*	rec)	/* in: pointer to record */
{
	return(page_rec_get_next_low(rec, page_rec_is_comp(rec)));
}

/****************************************************************
Sets the pointer to the next record on the page. */
UNIV_INLINE
void
page_rec_set_next(
/*==============*/
	rec_t*	rec,		/* in: pointer to record,
				must not be page supremum */
	rec_t*	next)		/* in: pointer to next record,
				must not be page infimum */
{
	ulint	offs;

	ut_ad(page_rec_check(rec));
	ut_ad(!page_rec_is_supremum(rec));
	ut_ad(rec != next);

	ut_ad(!next || !page_rec_is_infimum(next));
	ut_ad(!next || page_align(rec) == page_align(next));

	if (UNIV_LIKELY(next != NULL)) {
		offs = page_offset(next);
	} else {
		offs = 0;
	}

	if (page_rec_is_comp(rec)) {
		rec_set_next_offs_new(rec, offs);
	} else {
		rec_set_next_offs_old(rec, offs);
	}
}

/****************************************************************
Gets the pointer to the previous record. */
UNIV_INLINE
const rec_t*
page_rec_get_prev_const(
/*====================*/
				/* out: pointer to previous record */
	const rec_t*	rec)	/* in: pointer to record, must not be page
				infimum */
{
	const page_dir_slot_t*	slot;
	ulint			slot_no;
	const rec_t*		rec2;
	const rec_t*		prev_rec = NULL;
	const page_t*		page;

	ut_ad(page_rec_check(rec));

	page = page_align(rec);

	ut_ad(!page_rec_is_infimum(rec));

	slot_no = page_dir_find_owner_slot(rec);

	ut_a(slot_no != 0);

	slot = page_dir_get_nth_slot(page, slot_no - 1);

	rec2 = page_dir_slot_get_rec(slot);

	if (page_is_comp(page)) {
		while (rec != rec2) {
			prev_rec = rec2;
			rec2 = page_rec_get_next_low(rec2, TRUE);
		}
	} else {
		while (rec != rec2) {
			prev_rec = rec2;
			rec2 = page_rec_get_next_low(rec2, FALSE);
		}
	}

	ut_a(prev_rec);

	return(prev_rec);
}

/****************************************************************
Gets the pointer to the previous record. */
UNIV_INLINE
rec_t*
page_rec_get_prev(
/*==============*/
			/* out: pointer to previous record */
	rec_t*	rec)	/* in: pointer to record, must not be page
			infimum */
{
	return((rec_t*) page_rec_get_prev_const(rec));
}

/*******************************************************************
Looks for the record which owns the given record. */
UNIV_INLINE
rec_t*
page_rec_find_owner_rec(
/*====================*/
			/* out: the owner record */
	rec_t*	rec)	/* in: the physical record */
{
	ut_ad(page_rec_check(rec));

	if (page_rec_is_comp(rec)) {
		while (rec_get_n_owned_new(rec) == 0) {
			rec = page_rec_get_next(rec);
		}
	} else {
		while (rec_get_n_owned_old(rec) == 0) {
			rec = page_rec_get_next(rec);
		}
	}

	return(rec);
}

/**************************************************************
Returns the base extra size of a physical record.  This is the
size of the fixed header, independent of the record size. */
UNIV_INLINE
ulint
page_rec_get_base_extra_size(
/*=========================*/
				/* out: REC_N_NEW_EXTRA_BYTES
				or REC_N_OLD_EXTRA_BYTES */
	const rec_t*	rec)	/* in: physical record */
{
#if REC_N_NEW_EXTRA_BYTES + 1 != REC_N_OLD_EXTRA_BYTES
# error "REC_N_NEW_EXTRA_BYTES + 1 != REC_N_OLD_EXTRA_BYTES"
#endif
	return(REC_N_NEW_EXTRA_BYTES + (ulint) !page_rec_is_comp(rec));
}

/****************************************************************
Returns the sum of the sizes of the records in the record list, excluding
the infimum and supremum records. */
UNIV_INLINE
ulint
page_get_data_size(
/*===============*/
				/* out: data in bytes */
	const page_t*	page)	/* in: index page */
{
	ulint	ret;

	ret = (ulint)(page_header_get_field(page, PAGE_HEAP_TOP)
		      - (page_is_comp(page)
			 ? PAGE_NEW_SUPREMUM_END
			 : PAGE_OLD_SUPREMUM_END)
		      - page_header_get_field(page, PAGE_GARBAGE));

	ut_ad(ret < UNIV_PAGE_SIZE);

	return(ret);
}


/****************************************************************
Allocates a block of memory from the free list of an index page. */
UNIV_INTERN
void
page_mem_alloc_free(
/*================*/
	page_t*		page,	/* in/out: index page */
	page_zip_des_t*	page_zip,/* in/out: compressed page with enough
				space available for inserting the record,
				or NULL */
	rec_t*		next_rec,/* in: pointer to the new head of the
				free record list */
	ulint		need)	/* in: number of bytes allocated */
{
	ulint		garbage;

#ifdef UNIV_DEBUG
	const rec_t*	old_rec	= page_header_get_ptr(page, PAGE_FREE);
	ulint		next_offs;

	ut_ad(old_rec);
	next_offs = rec_get_next_offs(old_rec, page_is_comp(page));
	ut_ad(next_rec == (next_offs ? page + next_offs : NULL));
#endif

	page_header_set_ptr(page, page_zip, PAGE_FREE, next_rec);

	garbage = page_header_get_field(page, PAGE_GARBAGE);
	ut_ad(garbage >= need);

	page_header_set_field(page, page_zip, PAGE_GARBAGE, garbage - need);
}

/*****************************************************************
Calculates free space if a page is emptied. */
UNIV_INLINE
ulint
page_get_free_space_of_empty(
/*=========================*/
				/* out: free space */
	ulint	comp)		/* in: nonzero=compact page layout */
{
	if (UNIV_LIKELY(comp)) {
		return((ulint)(UNIV_PAGE_SIZE
			       - PAGE_NEW_SUPREMUM_END
			       - PAGE_DIR
			       - 2 * PAGE_DIR_SLOT_SIZE));
	}

	return((ulint)(UNIV_PAGE_SIZE
		       - PAGE_OLD_SUPREMUM_END
		       - PAGE_DIR
		       - 2 * PAGE_DIR_SLOT_SIZE));
}

/****************************************************************
Each user record on a page, and also the deleted user records in the heap
takes its size plus the fraction of the dir cell size /
PAGE_DIR_SLOT_MIN_N_OWNED bytes for it. If the sum of these exceeds the
value of page_get_free_space_of_empty, the insert is impossible, otherwise
it is allowed. This function returns the maximum combined size of records
which can be inserted on top of the record heap. */
UNIV_INLINE
ulint
page_get_max_insert_size(
/*=====================*/
				/* out: maximum combined size for
				inserted records */
	const page_t*	page,	/* in: index page */
	ulint		n_recs)	/* in: number of records */
{
	ulint	occupied;
	ulint	free_space;

	if (page_is_comp(page)) {
		occupied = page_header_get_field(page, PAGE_HEAP_TOP)
			- PAGE_NEW_SUPREMUM_END
			+ page_dir_calc_reserved_space(
				n_recs + page_dir_get_n_heap(page) - 2);

		free_space = page_get_free_space_of_empty(TRUE);
	} else {
		occupied = page_header_get_field(page, PAGE_HEAP_TOP)
			- PAGE_OLD_SUPREMUM_END
			+ page_dir_calc_reserved_space(
				n_recs + page_dir_get_n_heap(page) - 2);

		free_space = page_get_free_space_of_empty(FALSE);
	}

	/* Above the 'n_recs +' part reserves directory space for the new
	inserted records; the '- 2' excludes page infimum and supremum
	records */

	if (occupied > free_space) {

		return(0);
	}

	return(free_space - occupied);
}

/****************************************************************
Returns the maximum combined size of records which can be inserted on top
of the record heap if a page is first reorganized. */
UNIV_INLINE
ulint
page_get_max_insert_size_after_reorganize(
/*======================================*/
				/* out: maximum combined size for
				inserted records */
	const page_t*	page,	/* in: index page */
	ulint		n_recs)	/* in: number of records */
{
	ulint	occupied;
	ulint	free_space;

	occupied = page_get_data_size(page)
		+ page_dir_calc_reserved_space(n_recs + page_get_n_recs(page));

	free_space = page_get_free_space_of_empty(page_is_comp(page));

	if (occupied > free_space) {

		return(0);
	}

	return(free_space - occupied);
}

/****************************************************************
Puts a record to free list. */
UNIV_INLINE
void
page_mem_free(
/*==========*/
	page_t*		page,	/* in/out: index page */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	rec_t*		rec,	/* in: pointer to the (origin of) record */
	dict_index_t*	index,	/* in: index of rec */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	rec_t*		free;
	ulint		garbage;

	ut_ad(rec_offs_validate(rec, index, offsets));
	free = page_header_get_ptr(page, PAGE_FREE);

	page_rec_set_next(rec, free);
	page_header_set_ptr(page, page_zip, PAGE_FREE, rec);

	garbage = page_header_get_field(page, PAGE_GARBAGE);

	page_header_set_field(page, page_zip, PAGE_GARBAGE,
			      garbage + rec_offs_size(offsets));

	if (UNIV_LIKELY_NULL(page_zip)) {
		page_zip_dir_delete(page_zip, rec, index, offsets, free);
	} else {
		page_header_set_field(page, page_zip, PAGE_N_RECS,
				      page_get_n_recs(page) - 1);
	}
}

#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE	UNIV_INLINE_ORIGINAL
#endif