mariadb/page/page0cur.c

/************************************************************************
The page cursor

(c) 1994-1996 Innobase Oy

Created 10/4/1994 Heikki Tuuri
*************************************************************************/

#include "page0cur.h"
#ifdef UNIV_NONINL
#include "page0cur.ic"
#endif

#include "page0zip.h"
#include "rem0cmp.h"
#include "mtr0log.h"
#include "log0recv.h"
#include "rem0cmp.h"

static ulint	page_rnd	= 976722341;

#ifdef PAGE_CUR_ADAPT
# ifdef UNIV_SEARCH_PERF_STAT
ulint	page_cur_short_succ	= 0;
# endif /* UNIV_SEARCH_PERF_STAT */

/********************************************************************
Tries a search shortcut based on the last insert. */
UNIV_INLINE
ibool
page_cur_try_search_shortcut(
/*=========================*/
				/* out: TRUE on success */
	page_t*		page,	/* in: index page */
	dict_index_t*	index,	/* in: record descriptor */
	dtuple_t*	tuple,	/* in: data tuple */
	ulint*		iup_matched_fields,
				/* in/out: already matched fields in upper
				limit record */
	ulint*		iup_matched_bytes,
				/* in/out: already matched bytes in a field
				not yet completely matched */
	ulint*		ilow_matched_fields,
				/* in/out: already matched fields in lower
				limit record */
	ulint*		ilow_matched_bytes,
				/* in/out: already matched bytes in a field
				not yet completely matched */
	page_cur_t*	cursor) /* out: page cursor */
{
	rec_t*	rec;
	rec_t*	next_rec;
	ulint	low_match;
	ulint	low_bytes;
	ulint	up_match;
	ulint	up_bytes;
#ifdef UNIV_SEARCH_DEBUG
	page_cur_t cursor2;
#endif
	ibool		success		= FALSE;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	*offsets_ = (sizeof offsets_) / sizeof *offsets_;

	ut_ad(dtuple_check_typed(tuple));

	rec = page_header_get_ptr(page, PAGE_LAST_INSERT);
	offsets = rec_get_offsets(rec, index, offsets,
				dtuple_get_n_fields(tuple), &heap);

	ut_ad(rec);
	ut_ad(page_rec_is_user_rec(rec));

	ut_pair_min(&low_match, &low_bytes,
			*ilow_matched_fields, *ilow_matched_bytes,
			*iup_matched_fields, *iup_matched_bytes);

	up_match = low_match;
	up_bytes = low_bytes;

	if (page_cmp_dtuple_rec_with_match(tuple, rec, offsets,
						&low_match, &low_bytes) < 0) {
		goto exit_func;
	}

	next_rec = page_rec_get_next(rec);
	offsets = rec_get_offsets(next_rec, index, offsets,
				dtuple_get_n_fields(tuple), &heap);

	if (page_cmp_dtuple_rec_with_match(tuple, next_rec, offsets,
						&up_match, &up_bytes) >= 0) {
		goto exit_func;
	}

	cursor->rec = rec;

#ifdef UNIV_SEARCH_DEBUG
	page_cur_search_with_match(page, index, tuple, PAGE_CUR_DBG,
						iup_matched_fields,
						iup_matched_bytes,
						ilow_matched_fields,
						ilow_matched_bytes,
						&cursor2);
	ut_a(cursor2.rec == cursor->rec);

	if (next_rec != page_get_supremum_rec(page)) {

		ut_a(*iup_matched_fields == up_match);
		ut_a(*iup_matched_bytes == up_bytes);
	}

	ut_a(*ilow_matched_fields == low_match);
	ut_a(*ilow_matched_bytes == low_bytes);
#endif
	if (!page_rec_is_supremum(next_rec)) {

		*iup_matched_fields = up_match;
		*iup_matched_bytes = up_bytes;
	}

	*ilow_matched_fields = low_match;
	*ilow_matched_bytes = low_bytes;

#ifdef UNIV_SEARCH_PERF_STAT
	page_cur_short_succ++;
#endif
	success = TRUE;
exit_func:
	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}
	return(success);
}

#endif

#ifdef PAGE_CUR_LE_OR_EXTENDS
/********************************************************************
Checks if the nth field in a record is a character type field which extends
the nth field in tuple, i.e., the field is longer or equal in length and has
common first characters. */
static
ibool
page_cur_rec_field_extends(
/*=======================*/
				/* out: TRUE if rec field
				extends tuple field */
	dtuple_t*	tuple,	/* in: data tuple */
	rec_t*		rec,	/* in: record */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		n)	/* in: compare nth field */
{
	dtype_t* type;
	dfield_t* dfield;
	byte*	  rec_f;
	ulint	  rec_f_len;

	ut_ad(rec_offs_validate(rec, NULL, offsets));
	dfield = dtuple_get_nth_field(tuple, n);

	type = dfield_get_type(dfield);

	rec_f = rec_get_nth_field(rec, offsets, n, &rec_f_len);

	if (type->mtype == DATA_VARCHAR
	   || type->mtype == DATA_CHAR
	   || type->mtype == DATA_FIXBINARY
	   || type->mtype == DATA_BINARY
	   || type->mtype == DATA_BLOB
	   || type->mtype == DATA_VARMYSQL
	   || type->mtype == DATA_MYSQL) {

		if (dfield_get_len(dfield) != UNIV_SQL_NULL
			&& rec_f_len != UNIV_SQL_NULL
			&& rec_f_len >= dfield_get_len(dfield)
			&& 0 == cmp_data_data_slow(type,
				dfield_get_data(dfield),
				dfield_get_len(dfield),
				rec_f, dfield_get_len(dfield))) {

			return(TRUE);
		}
	}

	return(FALSE);
}
#endif /* PAGE_CUR_LE_OR_EXTENDS */

/********************************************************************
Searches the right position for a page cursor. */

void
page_cur_search_with_match(
/*=======================*/
	page_t*		page,	/* in: index page */
	dict_index_t*	index,	/* in: record descriptor */
	dtuple_t*	tuple,	/* in: data tuple */
	ulint		mode,	/* in: PAGE_CUR_L, PAGE_CUR_LE, PAGE_CUR_G,
				or PAGE_CUR_GE */
	ulint*		iup_matched_fields,
				/* in/out: already matched fields in upper
				limit record */
	ulint*		iup_matched_bytes,
				/* in/out: already matched bytes in a field
				not yet completely matched */
	ulint*		ilow_matched_fields,
				/* in/out: already matched fields in lower
				limit record */
	ulint*		ilow_matched_bytes,
				/* in/out: already matched bytes in a field
				not yet completely matched */
	page_cur_t*	cursor) /* out: page cursor */
{
	ulint	up;
	ulint	low;
	ulint	mid;
	page_dir_slot_t* slot;
	rec_t*	up_rec;
	rec_t*	low_rec;
	rec_t*	mid_rec;
	ulint	up_matched_fields;
	ulint	up_matched_bytes;
	ulint	low_matched_fields;
	ulint	low_matched_bytes;
	ulint	cur_matched_fields;
	ulint	cur_matched_bytes;
	int	cmp;
#ifdef UNIV_SEARCH_DEBUG
	int	dbg_cmp;
	ulint	dbg_matched_fields;
	ulint	dbg_matched_bytes;
#endif
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	*offsets_ = (sizeof offsets_) / sizeof *offsets_;

	ut_ad(page && tuple && iup_matched_fields && iup_matched_bytes
		&& ilow_matched_fields && ilow_matched_bytes && cursor);
	ut_ad(dtuple_validate(tuple));
	ut_ad(dtuple_check_typed(tuple));
#ifdef UNIV_DEBUG
# ifdef PAGE_CUR_DBG
	if (mode != PAGE_CUR_DBG)
# endif /* PAGE_CUR_DBG */
# ifdef PAGE_CUR_LE_OR_EXTENDS
		if (mode != PAGE_CUR_LE_OR_EXTENDS)
# endif /* PAGE_CUR_LE_OR_EXTENDS */
	ut_ad((mode == PAGE_CUR_L) || (mode == PAGE_CUR_LE)
		|| (mode == PAGE_CUR_G) || (mode == PAGE_CUR_GE));
#endif /* UNIV_DEBUG */

	page_check_dir(page);

#ifdef PAGE_CUR_ADAPT
	if (page_is_leaf(page)
		&& (mode == PAGE_CUR_LE)
		&& (page_header_get_field(page, PAGE_N_DIRECTION) > 3)
		&& (page_header_get_ptr(page, PAGE_LAST_INSERT))
		&& (page_header_get_field(page, PAGE_DIRECTION) == PAGE_RIGHT)) {

		if (page_cur_try_search_shortcut(page, index, tuple,
				iup_matched_fields, iup_matched_bytes,
				ilow_matched_fields, ilow_matched_bytes,
				cursor)) {
			return;
		}
	}
# ifdef PAGE_CUR_DBG
	if (mode == PAGE_CUR_DBG) {
		mode = PAGE_CUR_LE;
	}
# endif
#endif

	/* The following flag does not work for non-latin1 char sets because
	cmp_full_field does not tell how many bytes matched */
#ifdef PAGE_CUR_LE_OR_EXTENDS
	ut_a(mode != PAGE_CUR_LE_OR_EXTENDS);
#endif /* PAGE_CUR_LE_OR_EXTENDS */

	/* If mode PAGE_CUR_G is specified, we are trying to position the
	cursor to answer a query of the form "tuple < X", where tuple is
	the input parameter, and X denotes an arbitrary physical record on
	the page. We want to position the cursor on the first X which
	satisfies the condition. */

	up_matched_fields  = *iup_matched_fields;
	up_matched_bytes   = *iup_matched_bytes;
	low_matched_fields = *ilow_matched_fields;
	low_matched_bytes  = *ilow_matched_bytes;

	/* Perform binary search. First the search is done through the page
	directory, after that as a linear search in the list of records
	owned by the upper limit directory slot. */

	low = 0;
	up = page_dir_get_n_slots(page) - 1;

	/* Perform binary search until the lower and upper limit directory
	slots come to the distance 1 of each other */

	while (up - low > 1) {
		mid = (low + up) / 2;
		slot = page_dir_get_nth_slot(page, mid);
		mid_rec = page_dir_slot_get_rec(slot);

		ut_pair_min(&cur_matched_fields, &cur_matched_bytes,
				low_matched_fields, low_matched_bytes,
				up_matched_fields, up_matched_bytes);

		offsets = rec_get_offsets(mid_rec, index, offsets,
					dtuple_get_n_fields_cmp(tuple), &heap);

		cmp = cmp_dtuple_rec_with_match(tuple, mid_rec, offsets,
						&cur_matched_fields,
						&cur_matched_bytes);
		if (UNIV_LIKELY(cmp > 0)) {
low_slot_match:
			low = mid;
			low_matched_fields = cur_matched_fields;
			low_matched_bytes = cur_matched_bytes;

		} else if (UNIV_LIKELY(cmp /* == -1 */)) {
#ifdef PAGE_CUR_LE_OR_EXTENDS
			if (mode == PAGE_CUR_LE_OR_EXTENDS
				&& page_cur_rec_field_extends(tuple, mid_rec,
					offsets, cur_matched_fields)) {

				goto low_slot_match;
			}
#endif /* PAGE_CUR_LE_OR_EXTENDS */
up_slot_match:
			up = mid;
			up_matched_fields = cur_matched_fields;
			up_matched_bytes = cur_matched_bytes;

		} else if (mode == PAGE_CUR_G || mode == PAGE_CUR_LE
#ifdef PAGE_CUR_LE_OR_EXTENDS
			   || mode == PAGE_CUR_LE_OR_EXTENDS
#endif /* PAGE_CUR_LE_OR_EXTENDS */
		) {

			goto low_slot_match;
		} else {

			goto up_slot_match;
		}
	}

	slot = page_dir_get_nth_slot(page, low);
	low_rec = page_dir_slot_get_rec(slot);
	slot = page_dir_get_nth_slot(page, up);
	up_rec = page_dir_slot_get_rec(slot);

	/* Perform linear search until the upper and lower records come to
	distance 1 of each other. */

	while (page_rec_get_next(low_rec) != up_rec) {

		mid_rec = page_rec_get_next(low_rec);

		ut_pair_min(&cur_matched_fields, &cur_matched_bytes,
				low_matched_fields, low_matched_bytes,
				up_matched_fields, up_matched_bytes);

		offsets = rec_get_offsets(mid_rec, index, offsets,
					dtuple_get_n_fields_cmp(tuple), &heap);

		cmp = cmp_dtuple_rec_with_match(tuple, mid_rec, offsets,
						&cur_matched_fields,
						&cur_matched_bytes);
		if (UNIV_LIKELY(cmp > 0)) {
low_rec_match:
			low_rec = mid_rec;
			low_matched_fields = cur_matched_fields;
			low_matched_bytes = cur_matched_bytes;

		} else if (UNIV_LIKELY(cmp /* == -1 */)) {
#ifdef PAGE_CUR_LE_OR_EXTENDS
			if (mode == PAGE_CUR_LE_OR_EXTENDS
				&& page_cur_rec_field_extends(tuple, mid_rec,
					offsets, cur_matched_fields)) {

				goto low_rec_match;
			}
#endif /* PAGE_CUR_LE_OR_EXTENDS */
up_rec_match:
			up_rec = mid_rec;
			up_matched_fields = cur_matched_fields;
			up_matched_bytes = cur_matched_bytes;
		} else if (mode == PAGE_CUR_G || mode == PAGE_CUR_LE
#ifdef PAGE_CUR_LE_OR_EXTENDS
			   || mode == PAGE_CUR_LE_OR_EXTENDS
#endif /* PAGE_CUR_LE_OR_EXTENDS */
		) {

			goto low_rec_match;
		} else {

			goto up_rec_match;
		}
	}

#ifdef UNIV_SEARCH_DEBUG

	/* Check that the lower and upper limit records have the
	right alphabetical order compared to tuple. */
	dbg_matched_fields = 0;
	dbg_matched_bytes = 0;

	offsets = rec_get_offsets(low_rec, index, offsets,
						ULINT_UNDEFINED, &heap);
	dbg_cmp = page_cmp_dtuple_rec_with_match(tuple, low_rec, offsets,
						&dbg_matched_fields,
						&dbg_matched_bytes);
	if (mode == PAGE_CUR_G) {
		ut_a(dbg_cmp >= 0);
	} else if (mode == PAGE_CUR_GE) {
		ut_a(dbg_cmp == 1);
	} else if (mode == PAGE_CUR_L) {
		ut_a(dbg_cmp == 1);
	} else if (mode == PAGE_CUR_LE) {
		ut_a(dbg_cmp >= 0);
	}

	if (low_rec != page_get_infimum_rec(page)) {

		ut_a(low_matched_fields == dbg_matched_fields);
		ut_a(low_matched_bytes == dbg_matched_bytes);
	}

	dbg_matched_fields = 0;
	dbg_matched_bytes = 0;

	offsets = rec_get_offsets(up_rec, index, offsets,
						ULINT_UNDEFINED, &heap);
	dbg_cmp = page_cmp_dtuple_rec_with_match(tuple, up_rec, offsets,
						&dbg_matched_fields,
						&dbg_matched_bytes);
	if (mode == PAGE_CUR_G) {
		ut_a(dbg_cmp == -1);
	} else if (mode == PAGE_CUR_GE) {
		ut_a(dbg_cmp <= 0);
	} else if (mode == PAGE_CUR_L) {
		ut_a(dbg_cmp <= 0);
	} else if (mode == PAGE_CUR_LE) {
		ut_a(dbg_cmp == -1);
	}

	if (up_rec != page_get_supremum_rec(page)) {

		ut_a(up_matched_fields == dbg_matched_fields);
		ut_a(up_matched_bytes == dbg_matched_bytes);
	}
#endif
	if (mode <= PAGE_CUR_GE) {
		cursor->rec = up_rec;
	} else {
		cursor->rec = low_rec;
	}

	*iup_matched_fields  = up_matched_fields;
	*iup_matched_bytes   = up_matched_bytes;
	*ilow_matched_fields = low_matched_fields;
	*ilow_matched_bytes  = low_matched_bytes;
	if (UNIV_LIKELY_NULL(heap)) {
		mem_heap_free(heap);
	}
}

/***************************************************************
Positions a page cursor on a randomly chosen user record on a page. If there
are no user records, sets the cursor on the infimum record. */

void
page_cur_open_on_rnd_user_rec(
/*==========================*/
	page_t*		page,	/* in: page */
	page_cur_t*	cursor)	/* in/out: page cursor */
{
	ulint	rnd;
	rec_t*	rec;

	if (UNIV_UNLIKELY(page_get_n_recs(page) == 0)) {
		page_cur_position(page_get_infimum_rec(page), cursor);

		return;
	}

	page_rnd += 87584577;

	rnd = page_rnd % page_get_n_recs(page);

	rec = page_get_infimum_rec(page);

	rec = page_rec_get_next(rec);

	while (rnd > 0) {
		rec = page_rec_get_next(rec);

		rnd--;
	}

	page_cur_position(rec, cursor);
}

/***************************************************************
Writes the log record of a record insert on a page. */
static
void
page_cur_insert_rec_write_log(
/*==========================*/
	rec_t*		insert_rec,	/* in: inserted physical record */
	ulint		rec_size,	/* in: insert_rec size */
	rec_t*		cursor_rec,	/* in: record the
					cursor is pointing to */
	dict_index_t*	index,		/* in: record descriptor */
	mtr_t*		mtr)		/* in: mini-transaction handle */
{
	ulint	cur_rec_size;
	ulint	extra_size;
	ulint	cur_extra_size;
	const byte* ins_ptr;
	byte*	log_ptr;
	const byte* log_end;
	ulint	i;

	ut_a(rec_size < UNIV_PAGE_SIZE);
	ut_ad(buf_frame_align(insert_rec) == buf_frame_align(cursor_rec));
	ut_ad(!page_rec_is_comp(insert_rec)
		== !dict_table_is_comp(index->table));

	{
		mem_heap_t*	heap		= NULL;
		ulint		cur_offs_[REC_OFFS_NORMAL_SIZE];
		ulint		ins_offs_[REC_OFFS_NORMAL_SIZE];

		ulint*		cur_offs;
		ulint*		ins_offs;

		*cur_offs_ = (sizeof cur_offs_) / sizeof *cur_offs_;
		*ins_offs_ = (sizeof ins_offs_) / sizeof *ins_offs_;

		cur_offs = rec_get_offsets(cursor_rec, index, cur_offs_,
						ULINT_UNDEFINED, &heap);
		ins_offs = rec_get_offsets(insert_rec, index, ins_offs_,
						ULINT_UNDEFINED, &heap);

		extra_size = rec_offs_extra_size(ins_offs);
		cur_extra_size = rec_offs_extra_size(cur_offs);
		ut_ad(rec_size == rec_offs_size(ins_offs));
		cur_rec_size = rec_offs_size(cur_offs);

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

	ins_ptr = insert_rec - extra_size;

	i = 0;

	if (cur_extra_size == extra_size) {
		ulint		min_rec_size = ut_min(cur_rec_size, rec_size);

		const byte*	cur_ptr = cursor_rec - cur_extra_size;

		/* Find out the first byte in insert_rec which differs from
		cursor_rec; skip the bytes in the record info */

		do {
			if (*ins_ptr == *cur_ptr) {
				i++;
				ins_ptr++;
				cur_ptr++;
			} else if ((i < extra_size)
				   && (i >= extra_size -
				       page_rec_get_base_extra_size(
							insert_rec))) {
				i = extra_size;
				ins_ptr = insert_rec;
				cur_ptr = cursor_rec;
			} else {
				break;
			}
		} while (i < min_rec_size);
	}

	if (mtr_get_log_mode(mtr) != MTR_LOG_SHORT_INSERTS) {

		if (page_rec_is_comp(insert_rec)) {
			log_ptr = mlog_open_and_write_index(mtr, insert_rec,
					index, MLOG_COMP_REC_INSERT,
					2 + 5 + 1 + 5 + 5 + MLOG_BUF_MARGIN);
			if (UNIV_UNLIKELY(!log_ptr)) {
				/* Logging in mtr is switched off
				during crash recovery: in that case
				mlog_open returns NULL */
				return;
			}
		} else {
			log_ptr = mlog_open(mtr, 11
					+ 2 + 5 + 1 + 5 + 5 + MLOG_BUF_MARGIN);
			if (UNIV_UNLIKELY(!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(
				insert_rec, MLOG_REC_INSERT, log_ptr, mtr);
		}

		log_end = &log_ptr[2 + 5 + 1 + 5 + 5 + MLOG_BUF_MARGIN];
		/* Write the cursor rec offset as a 2-byte ulint */
		mach_write_to_2(log_ptr, cursor_rec
					- buf_frame_align(cursor_rec));
		log_ptr += 2;
	} else {
		log_ptr = mlog_open(mtr, 5 + 1 + 5 + 5 + MLOG_BUF_MARGIN);
		if (!log_ptr) {
			/* Logging in mtr is switched off during crash
			recovery: in that case mlog_open returns NULL */
			return;
		}
		log_end = &log_ptr[5 + 1 + 5 + 5 + MLOG_BUF_MARGIN];
	}

	if (page_rec_is_comp(insert_rec)) {
		if (UNIV_UNLIKELY
		    (rec_get_info_and_status_bits(insert_rec, TRUE) !=
		     rec_get_info_and_status_bits(cursor_rec, TRUE))) {

			goto need_extra_info;
		}
	} else {
		if (UNIV_UNLIKELY
		    (rec_get_info_and_status_bits(insert_rec, FALSE) !=
		     rec_get_info_and_status_bits(cursor_rec, FALSE))) {

			goto need_extra_info;
		}
	}

	if (extra_size != cur_extra_size || rec_size != cur_rec_size) {
need_extra_info:
		/* Write the record end segment length
		and the extra info storage flag */
		log_ptr += mach_write_compressed(log_ptr,
					2 * (rec_size - i) + 1);

		/* Write the info bits */
		mach_write_to_1(log_ptr,
				rec_get_info_and_status_bits(insert_rec,
				page_rec_is_comp(insert_rec)));
		log_ptr++;

		/* Write the record origin offset */
		log_ptr += mach_write_compressed(log_ptr, extra_size);

		/* Write the mismatch index */
		log_ptr += mach_write_compressed(log_ptr, i);

		ut_a(i < UNIV_PAGE_SIZE);
		ut_a(extra_size < UNIV_PAGE_SIZE);
	} else {
		/* Write the record end segment length
		and the extra info storage flag */
		log_ptr += mach_write_compressed(log_ptr, 2 * (rec_size - i));
	}

	/* Write to the log the inserted index record end segment which
	differs from the cursor record */

	rec_size -= i;

	if (log_ptr + rec_size <= log_end) {
		memcpy(log_ptr, ins_ptr, rec_size);
		mlog_close(mtr, log_ptr + rec_size);
	} else {
		mlog_close(mtr, log_ptr);
		ut_a(rec_size < UNIV_PAGE_SIZE);
		mlog_catenate_string(mtr, ins_ptr, rec_size);
	}
}

/***************************************************************
Parses a log record of a record insert on a page. */

byte*
page_cur_parse_insert_rec(
/*======================*/
				/* out: end of log record or NULL */
	ibool		is_short,/* in: TRUE if short inserts */
	byte*		ptr,	/* in: buffer */
	byte*		end_ptr,/* in: buffer end */
	dict_index_t*	index,	/* in: record descriptor */
	page_t*		page,	/* in/out: page or NULL */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	mtr_t*		mtr)	/* in: mtr or NULL */
{
	ulint	offset = 0; /* remove warning */
	ulint	origin_offset;
	ulint	end_seg_len;
	ulint	mismatch_index;
	rec_t*	cursor_rec;
	byte	buf1[1024];
	byte*	buf;
	byte*	ptr2 = ptr;
	ulint	info_and_status_bits = 0; /* remove warning */
	page_cur_t cursor;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	*offsets_ = (sizeof offsets_) / sizeof *offsets_;

	if (!is_short) {
		/* Read the cursor rec offset as a 2-byte ulint */

		if (end_ptr < ptr + 2) {

			return(NULL);
		}

		offset = mach_read_from_2(ptr);

		if (offset >= UNIV_PAGE_SIZE) {

			recv_sys->found_corrupt_log = TRUE;

			return(NULL);
		}

		ptr += 2;
	}

	ptr = mach_parse_compressed(ptr, end_ptr, &end_seg_len);

	if (ptr == NULL) {

		return(NULL);
	}

	if (UNIV_UNLIKELY(end_seg_len >= UNIV_PAGE_SIZE << 1)) {
		recv_sys->found_corrupt_log = TRUE;

		return(NULL);
	}

	if (end_seg_len & 0x1UL) {
		/* Read the info bits */

		if (end_ptr < ptr + 1) {

			return(NULL);
		}

		info_and_status_bits = mach_read_from_1(ptr);
		ptr++;

		ptr = mach_parse_compressed(ptr, end_ptr, &origin_offset);

		if (ptr == NULL) {

			return(NULL);
		}

		ut_a(origin_offset < UNIV_PAGE_SIZE);

		ptr = mach_parse_compressed(ptr, end_ptr, &mismatch_index);

		if (ptr == NULL) {

			return(NULL);
		}

		ut_a(mismatch_index < UNIV_PAGE_SIZE);
	}

	if (end_ptr < ptr + (end_seg_len >> 1)) {

		return(NULL);
	}

	if (page == NULL) {

		return(ptr + (end_seg_len >> 1));
	}

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

	/* Read from the log the inserted index record end segment which
	differs from the cursor record */

	if (is_short) {
		cursor_rec = page_rec_get_prev(page_get_supremum_rec(page));
	} else {
		cursor_rec = page + offset;
	}

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

	if (!(end_seg_len & 0x1UL)) {
		info_and_status_bits = rec_get_info_and_status_bits(
					cursor_rec, page_is_comp(page));
		origin_offset = rec_offs_extra_size(offsets);
		mismatch_index = rec_offs_size(offsets) - (end_seg_len >> 1);
	}

	end_seg_len >>= 1;

	if (mismatch_index + end_seg_len < sizeof buf1) {
		buf = buf1;
	} else {
		buf = mem_alloc(mismatch_index + end_seg_len);
	}

	/* Build the inserted record to buf */

        if (UNIV_UNLIKELY(mismatch_index >= UNIV_PAGE_SIZE)) {
		fprintf(stderr,
			"Is short %lu, info_and_status_bits %lu, offset %lu, "
			"o_offset %lu\n"
			"mismatch index %lu, end_seg_len %lu\n"
			"parsed len %lu\n",
			(ulong) is_short, (ulong) info_and_status_bits,
			(ulong) offset,
			(ulong) origin_offset,
			(ulong) mismatch_index, (ulong) end_seg_len,
			(ulong) (ptr - ptr2));

		fputs("Dump of 300 bytes of log:\n", stderr);
		ut_print_buf(stderr, ptr2, 300);

		buf_page_print(page);

		ut_error;
	}

	ut_memcpy(buf, rec_get_start(cursor_rec, offsets), mismatch_index);
	ut_memcpy(buf + mismatch_index, ptr, end_seg_len);

	if (page_is_comp(page)) {
		rec_set_info_and_status_bits(buf + origin_offset,
							info_and_status_bits);
	} else {
		rec_set_info_bits_old(buf + origin_offset,
							info_and_status_bits);
	}

	page_cur_position(cursor_rec, &cursor);

	offsets = rec_get_offsets(buf + origin_offset, index, offsets,
						ULINT_UNDEFINED, &heap);
	if (UNIV_UNLIKELY(!page_cur_rec_insert(&cursor, page_zip,
				buf + origin_offset, index, offsets, mtr))) {
		/* The redo log record should only have been written
		after the write was successful. */
		ut_error;
	}

	if (buf != buf1) {

		mem_free(buf);
	}

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

	return(ptr + end_seg_len);
}

/***************************************************************
Inserts a record next to page cursor. Returns pointer to inserted record if
succeed, i.e., enough space available, NULL otherwise. The record to be
inserted can be in a data tuple or as a physical record. The other parameter
must then be NULL. The cursor stays at the same position. */

rec_t*
page_cur_insert_rec_low(
/*====================*/
				/* out: pointer to record if succeed, NULL
				otherwise */
	page_cur_t*	cursor,	/* in: a page cursor */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	dict_index_t*	index,	/* in: record descriptor */
	rec_t*		rec,	/* in: pointer to a physical record */
	ulint*		offsets,/* in/out: rec_get_offsets(rec, index) */
	const ulint*	ext,	/* in: array of extern field numbers */
	ulint		n_ext,	/* in: number of elements in vec */
	mtr_t*		mtr)	/* in: mini-transaction handle */
{
	byte*		insert_buf	= NULL;
	ulint		rec_size;
	byte*		page;		/* the relevant page */
	rec_t*		last_insert;	/* cursor position at previous insert */
	rec_t*		insert_rec;	/* inserted record */
	ulint		heap_no;	/* heap number of the inserted record */
	rec_t*		current_rec;	/* current record after which the
					new record is inserted */

	ut_ad(cursor && mtr);
	ut_ad(rec_offs_validate(rec, index, offsets));

	page = page_cur_get_page(cursor);
	ut_ad(dict_table_is_comp(index->table)
			== (ibool) !!page_is_comp(page));

	ut_ad(!page_rec_is_supremum(cursor->rec));
	ut_ad(!page_zip || page_zip_validate(page_zip, page));

	/* 1. Get the size of the physical record in the page */
	rec_size = rec_offs_size(offsets);

	/* 2. Try to find suitable space from page memory management */
	if (UNIV_LIKELY_NULL(page_zip)
	    && !page_zip_alloc(page_zip, page, index, mtr, rec_size, 1)) {

		return(NULL);
	}

	insert_buf = page_header_get_ptr(page, PAGE_FREE);
	if (insert_buf) {
		/* Try to allocate from the head of the free list. */
		rec_t*		free_rec	= insert_buf;
		ulint		foffsets_[REC_OFFS_NORMAL_SIZE];
		ulint*		foffsets	= foffsets_;
		mem_heap_t*	heap		= NULL;

		*foffsets = sizeof(foffsets_) / sizeof *foffsets_;

		foffsets = rec_get_offsets(free_rec, index, foffsets,
					ULINT_UNDEFINED, &heap);
		if (rec_offs_size(foffsets) < rec_size) {
too_small:
			if (UNIV_LIKELY_NULL(heap)) {
				mem_heap_free(heap);
			}

			goto use_heap;
		}

		insert_buf -= rec_offs_extra_size(foffsets);

		if (page_is_comp(page)) {
			if (UNIV_LIKELY_NULL(page_zip)) {
				/* On compressed pages, do not
				relocate records from the free list.
				If extra_size would grow, use the heap. */
				lint	extra_size_diff
					= rec_offs_extra_size(offsets)
					- rec_offs_extra_size(foffsets);

				if (UNIV_UNLIKELY(extra_size_diff < 0)) {
					/* Add an offset to the extra_size. */
					if (rec_offs_size(foffsets)
					    < rec_size - extra_size_diff) {

						goto too_small;
					}

					insert_buf -= extra_size_diff;
				} else if (UNIV_UNLIKELY(extra_size_diff)) {
					/* Do not allow extra_size to grow */

					goto use_heap;
				}
			}

			heap_no = rec_get_heap_no_new(free_rec);
			page_mem_alloc_free(page, page_zip,
					rec_get_next_ptr(free_rec, TRUE),
					rec_size);
		} else {
			ut_ad(!page_zip);
			heap_no = rec_get_heap_no_old(free_rec);
			page_mem_alloc_free(page, NULL,
					rec_get_next_ptr(free_rec, FALSE),
					rec_size);
		}

		if (UNIV_LIKELY_NULL(heap)) {
			mem_heap_free(heap);
		}
	} else {
use_heap:
		insert_buf = page_mem_alloc_heap(
				page, page_zip, rec_size, &heap_no);

		if (UNIV_UNLIKELY(insert_buf == NULL)) {
			return(NULL);
		}

		if (UNIV_LIKELY_NULL(page_zip)) {
			page_zip_dir_add_slot(page_zip,
					dict_index_is_clust(index));
		}
	}

	/* 3. Create the record */
	insert_rec = rec_copy(insert_buf, rec, offsets);
	rec_offs_make_valid(insert_rec, index, offsets);

	/* Set the "extern storage" flags */
	if (UNIV_UNLIKELY(n_ext)) {
		rec_set_field_extern_bits(insert_rec, index, offsets,
				ext, n_ext);
	}

	/* 4. Insert the record in the linked list of records */
	current_rec = cursor->rec;

	{
		/* next record after current before the insertion */
		rec_t*	next_rec = page_rec_get_next(current_rec);
#ifdef UNIV_DEBUG
		if (page_is_comp(page)) {
			ut_ad(rec_get_status(current_rec)
				<= REC_STATUS_INFIMUM);
			ut_ad(rec_get_status(insert_rec) < REC_STATUS_INFIMUM);
			ut_ad(rec_get_status(next_rec) != REC_STATUS_INFIMUM);
		}
#endif
		page_rec_set_next(insert_rec, next_rec);
		page_rec_set_next(current_rec, insert_rec);
	}

	page_header_set_field(page, page_zip, PAGE_N_RECS,
				1 + page_get_n_recs(page));

	/* 5. Set the n_owned field in the inserted record to zero,
	and set the heap_no field */
	if (page_is_comp(page)) {
		rec_set_n_owned_new(insert_rec, NULL, 0);
		rec_set_heap_no_new(insert_rec, heap_no);
	} else {
		rec_set_n_owned_old(insert_rec, 0);
		rec_set_heap_no_old(insert_rec, heap_no);
	}

	/* 6. Update the last insertion info in page header */

	last_insert = page_header_get_ptr(page, PAGE_LAST_INSERT);
	ut_ad(!last_insert || !page_is_comp(page)
		|| rec_get_node_ptr_flag(last_insert)
		== rec_get_node_ptr_flag(insert_rec));

	if (UNIV_UNLIKELY(last_insert == NULL)) {
		page_header_set_field(page, page_zip, PAGE_DIRECTION,
							PAGE_NO_DIRECTION);
		page_header_set_field(page, page_zip, PAGE_N_DIRECTION, 0);

	} else if ((last_insert == current_rec)
		&& (page_header_get_field(page, PAGE_DIRECTION) != PAGE_LEFT)) {

		page_header_set_field(page, page_zip, PAGE_DIRECTION,
							PAGE_RIGHT);
		page_header_set_field(page, page_zip, PAGE_N_DIRECTION,
			page_header_get_field(page, PAGE_N_DIRECTION) + 1);

	} else if ((page_rec_get_next(insert_rec) == last_insert)
		&& (page_header_get_field(page, PAGE_DIRECTION) != PAGE_RIGHT)) {

		page_header_set_field(page, page_zip, PAGE_DIRECTION,
							PAGE_LEFT);
		page_header_set_field(page, page_zip, PAGE_N_DIRECTION,
			page_header_get_field(page, PAGE_N_DIRECTION) + 1);
	} else {
		page_header_set_field(page, page_zip, PAGE_DIRECTION,
							PAGE_NO_DIRECTION);
		page_header_set_field(page, page_zip, PAGE_N_DIRECTION, 0);
	}

	page_header_set_ptr(page, page_zip, PAGE_LAST_INSERT, insert_rec);

	/* 7. It remains to update the owner record. */
	{
		rec_t*	owner_rec	= page_rec_find_owner_rec(insert_rec);
		ulint	n_owned;
		if (page_is_comp(page)) {
			n_owned = rec_get_n_owned_new(owner_rec);
			rec_set_n_owned_new(owner_rec, NULL, n_owned + 1);
		} else {
			n_owned = rec_get_n_owned_old(owner_rec);
			rec_set_n_owned_old(owner_rec, n_owned + 1);
		}

		/* 8. Now we have incremented the n_owned field of the owner
		record. If the number exceeds PAGE_DIR_SLOT_MAX_N_OWNED,
		we have to split the corresponding directory slot in two. */

		if (UNIV_UNLIKELY(n_owned == PAGE_DIR_SLOT_MAX_N_OWNED)) {
			page_dir_split_slot(page, page_zip,
					page_dir_find_owner_slot(owner_rec));
		}
	}

	if (UNIV_LIKELY_NULL(page_zip)) {
		/* TODO: something similar to page_zip_dir_delete() */
		page_zip_dir_rewrite(page_zip, page);

		page_zip_write_rec(page_zip, insert_rec, index, offsets, 1);
	}

	/* 9. Write log record of the insert */
	page_cur_insert_rec_write_log(insert_rec, rec_size, current_rec,
				index, mtr);

	return(insert_rec);
}

/**************************************************************
Writes a log record of copying a record list end to a new created page. */
UNIV_INLINE
byte*
page_copy_rec_list_to_created_page_write_log(
/*=========================================*/
				/* out: 4-byte field where to
				write the log data length */
	page_t*		page,	/* in: index page */
	dict_index_t*	index,	/* in: record descriptor */
	mtr_t*		mtr)	/* in: mtr */
{
	byte*	log_ptr;

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

	log_ptr = mlog_open_and_write_index(mtr, page, index,
			page_is_comp(page)
			? MLOG_COMP_LIST_END_COPY_CREATED
			: MLOG_LIST_END_COPY_CREATED, 4);
	ut_a(log_ptr);
	mlog_close(mtr, log_ptr + 4);

	return(log_ptr);
}

/**************************************************************
Parses a log record of copying a record list end to a new created page. */

byte*
page_parse_copy_rec_list_to_created_page(
/*=====================================*/
				/* out: end of log record or NULL */
	byte*		ptr,	/* in: buffer */
	byte*		end_ptr,/* in: buffer end */
	dict_index_t*	index,	/* in: record descriptor */
	page_t*		page,	/* in/out: page or NULL */
	page_zip_des_t*	page_zip,/* in/out: compressed page or NULL */
	mtr_t*		mtr)	/* in: mtr or NULL */
{
	byte*	rec_end;
	ulint	log_data_len;

	if (ptr + 4 > end_ptr) {

		return(NULL);
	}

	log_data_len = mach_read_from_4(ptr);
	ptr += 4;

	rec_end = ptr + log_data_len;

	if (rec_end > end_ptr) {

		return(NULL);
	}

	if (!page) {

		return(rec_end);
	}

	while (ptr < rec_end) {
		ptr = page_cur_parse_insert_rec(TRUE, ptr, end_ptr,
						index, page, page_zip, mtr);
	}

	ut_a(ptr == rec_end);

	page_header_set_ptr(page, page_zip, PAGE_LAST_INSERT, NULL);
	page_header_set_field(page, page_zip, PAGE_DIRECTION,
							PAGE_NO_DIRECTION);
	page_header_set_field(page, page_zip, PAGE_N_DIRECTION, 0);

	return(rec_end);
}

/*****************************************************************
Copies records from page to a newly created page, from a given record onward,
including that record. Infimum and supremum records are not copied. */

void
page_copy_rec_list_end_to_created_page(
/*===================================*/
	page_t*		new_page,	/* in: index page to copy to */
	rec_t*		rec,		/* in: first record to copy */
	dict_index_t*	index,		/* in: record descriptor */
	mtr_t*		mtr)		/* in: mtr */
{
	page_dir_slot_t* slot = 0; /* remove warning */
	byte*	heap_top;
	rec_t*	insert_rec = 0; /* remove warning */
	rec_t*	prev_rec;
	ulint	count;
	ulint	n_recs;
	ulint	slot_index;
	ulint	rec_size;
	ulint	log_mode;
	byte*	log_ptr;
	ulint	log_data_len;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	*offsets_ = (sizeof offsets_) / sizeof *offsets_;

	ut_ad(page_dir_get_n_heap(new_page) == 2);
	ut_ad(ut_align_down(rec, UNIV_PAGE_SIZE) != new_page);
	ut_ad(page_rec_is_comp(rec) == page_is_comp(new_page));

	if (page_rec_is_infimum(rec)) {

		rec = page_rec_get_next(rec);
	}

	if (page_rec_is_supremum(rec)) {

		return;
	}

#ifdef UNIV_DEBUG
	/* To pass the debug tests we have to set these dummy values
	in the debug version */
	page_dir_set_n_slots(new_page, NULL, UNIV_PAGE_SIZE / 2);
	page_header_set_ptr(new_page, NULL, PAGE_HEAP_TOP,
					new_page + UNIV_PAGE_SIZE - 1);
#endif

	log_ptr = page_copy_rec_list_to_created_page_write_log(new_page,
								index, mtr);

	log_data_len = dyn_array_get_data_size(&(mtr->log));

	/* Individual inserts are logged in a shorter form */

	log_mode = mtr_set_log_mode(mtr, MTR_LOG_SHORT_INSERTS);

	prev_rec = page_get_infimum_rec(new_page);
	if (page_is_comp(new_page)) {
		heap_top = new_page + PAGE_NEW_SUPREMUM_END;
	} else {
		heap_top = new_page + PAGE_OLD_SUPREMUM_END;
	}
	count = 0;
	slot_index = 0;
	n_recs = 0;

	do {
		offsets = rec_get_offsets(rec, index, offsets,
					ULINT_UNDEFINED, &heap);
		insert_rec = rec_copy(heap_top, rec, offsets);

		if (page_is_comp(new_page)) {
			rec_set_next_offs_new(prev_rec,
				ut_align_offset(insert_rec, UNIV_PAGE_SIZE));

			rec_set_n_owned_new(insert_rec, NULL, 0);
			rec_set_heap_no_new(insert_rec, 2 + n_recs);
		} else {
			rec_set_next_offs_old(prev_rec,
				ut_align_offset(insert_rec, UNIV_PAGE_SIZE));

			rec_set_n_owned_old(insert_rec, 0);
			rec_set_heap_no_old(insert_rec, 2 + n_recs);
		}

		count++;
		n_recs++;

		if (UNIV_UNLIKELY(count ==
				(PAGE_DIR_SLOT_MAX_N_OWNED + 1) / 2)) {

			slot_index++;

			slot = page_dir_get_nth_slot(new_page, slot_index);

			page_dir_slot_set_rec(slot, insert_rec);
			page_dir_slot_set_n_owned(slot, NULL, count);

			count = 0;
		}

		rec_size = rec_offs_size(offsets);

		ut_ad(heap_top < new_page + UNIV_PAGE_SIZE);

		heap_top += rec_size;

		page_cur_insert_rec_write_log(insert_rec, rec_size, prev_rec,
								index, mtr);
		prev_rec = insert_rec;
		rec = page_rec_get_next(rec);
	} while (!page_rec_is_supremum(rec));

	if ((slot_index > 0) && (count + 1
				+ (PAGE_DIR_SLOT_MAX_N_OWNED + 1) / 2
				 <= PAGE_DIR_SLOT_MAX_N_OWNED)) {
		/* We can merge the two last dir slots. This operation is
		here to make this function imitate exactly the equivalent
		task made using page_cur_insert_rec, which we use in database
		recovery to reproduce the task performed by this function.
		To be able to check the correctness of recovery, it is good
		that it imitates exactly. */

		count += (PAGE_DIR_SLOT_MAX_N_OWNED + 1) / 2;

		page_dir_slot_set_n_owned(slot, NULL, 0);

		slot_index--;
	}

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

	log_data_len = dyn_array_get_data_size(&(mtr->log)) - log_data_len;

	ut_a(log_data_len < 100 * UNIV_PAGE_SIZE);

	mach_write_to_4(log_ptr, log_data_len);

	if (page_is_comp(new_page)) {
		rec_set_next_offs_new(insert_rec, PAGE_NEW_SUPREMUM);
	} else {
		rec_set_next_offs_old(insert_rec, PAGE_OLD_SUPREMUM);
	}

	slot = page_dir_get_nth_slot(new_page, 1 + slot_index);

	page_dir_slot_set_rec(slot, page_get_supremum_rec(new_page));
	page_dir_slot_set_n_owned(slot, NULL, count + 1);

	page_dir_set_n_slots(new_page, NULL, 2 + slot_index);
	page_header_set_ptr(new_page, NULL, PAGE_HEAP_TOP, heap_top);
	page_dir_set_n_heap(new_page, NULL, 2 + n_recs);
	page_header_set_field(new_page, NULL, PAGE_N_RECS, n_recs);

	page_header_set_ptr(new_page, NULL, PAGE_LAST_INSERT, NULL);
	page_header_set_field(new_page, NULL, PAGE_DIRECTION,
							PAGE_NO_DIRECTION);
	page_header_set_field(new_page, NULL, PAGE_N_DIRECTION, 0);

	/* Restore the log mode */

	mtr_set_log_mode(mtr, log_mode);
}

/***************************************************************
Writes log record of a record delete on a page. */
UNIV_INLINE
void
page_cur_delete_rec_write_log(
/*==========================*/
	rec_t*		rec,	/* in: record to be deleted */
	dict_index_t*	index,	/* in: record descriptor */
	mtr_t*		mtr)	/* in: mini-transaction handle */
{
	byte*	log_ptr;

	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_DELETE
			: MLOG_REC_DELETE, 2);

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

	/* Write the cursor rec offset as a 2-byte ulint */
	mach_write_to_2(log_ptr, ut_align_offset(rec, UNIV_PAGE_SIZE));

	mlog_close(mtr, log_ptr + 2);
}

/***************************************************************
Parses log record of a record delete on a page. */

byte*
page_cur_parse_delete_rec(
/*======================*/
				/* out: pointer to record end or NULL */
	byte*		ptr,	/* in: buffer */
	byte*		end_ptr,/* in: buffer end */
	dict_index_t*	index,	/* in: record descriptor */
	page_t*		page,	/* in/out: page or NULL */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	mtr_t*		mtr)	/* in: mtr or NULL */
{
	ulint		offset;
	page_cur_t	cursor;

	if (end_ptr < ptr + 2) {

		return(NULL);
	}

	/* Read the cursor rec offset as a 2-byte ulint */
	offset = mach_read_from_2(ptr);
	ptr += 2;

	ut_a(offset <= UNIV_PAGE_SIZE);

	if (page) {
		mem_heap_t*	heap		= NULL;
		ulint		offsets_[REC_OFFS_NORMAL_SIZE];
		rec_t*		rec		= page + offset;
		*offsets_ = (sizeof offsets_) / sizeof *offsets_;

		page_cur_position(rec, &cursor);
		ut_ad(!page_zip || page_is_comp(page));

		page_cur_delete_rec(&cursor, index,
				rec_get_offsets(rec, index, offsets_,
				ULINT_UNDEFINED, &heap), page_zip, mtr);
		if (UNIV_LIKELY_NULL(heap)) {
			mem_heap_free(heap);
		}
	}

	return(ptr);
}

/***************************************************************
Deletes a record at the page cursor. The cursor is moved to the next
record after the deleted one. */

void
page_cur_delete_rec(
/*================*/
	page_cur_t*	cursor,	/* in/out: a page cursor */
	dict_index_t*	index,	/* in: record descriptor */
	const ulint*	offsets,/* in: rec_get_offsets(cursor->rec, index) */
	page_zip_des_t*	page_zip,/* in/out: compressed page, or NULL */
	mtr_t*		mtr)	/* in: mini-transaction handle */
{
	page_dir_slot_t* cur_dir_slot;
	page_dir_slot_t* prev_slot;
	page_t*		page;
	rec_t*		current_rec;
	rec_t*		prev_rec	= NULL;
	rec_t*		next_rec;
	ulint		cur_slot_no;
	ulint		cur_n_owned;
	rec_t*		rec;

	ut_ad(cursor && mtr);

	page = page_cur_get_page(cursor);
	current_rec = cursor->rec;
	ut_ad(rec_offs_validate(current_rec, index, offsets));
	ut_ad(!!page_is_comp(page) == dict_table_is_comp(index->table));
	ut_ad(!page_zip || page_zip_validate(page_zip, page));

	/* The record must not be the supremum or infimum record. */
	ut_ad(page_rec_is_user_rec(current_rec));

	/* Save to local variables some data associated with current_rec */
	cur_slot_no = page_dir_find_owner_slot(current_rec);
	cur_dir_slot = page_dir_get_nth_slot(page, cur_slot_no);
	cur_n_owned = page_dir_slot_get_n_owned(cur_dir_slot);

	/* 0. Write the log record */
	page_cur_delete_rec_write_log(current_rec, index, mtr);

	/* 1. Reset the last insert info in the page header and increment
	the modify clock for the frame */

	page_header_set_ptr(page, page_zip, PAGE_LAST_INSERT, NULL);

	/* The page gets invalid for optimistic searches: increment the
	frame modify clock */

	buf_frame_modify_clock_inc(page);

	/* 2. Find the next and the previous record. Note that the cursor is
	left at the next record. */

	ut_ad(cur_slot_no > 0);
	prev_slot = page_dir_get_nth_slot(page, cur_slot_no - 1);

	rec = page_dir_slot_get_rec(prev_slot);

	/* rec now points to the record of the previous directory slot. Look
	for the immediate predecessor of current_rec in a loop. */

	while(current_rec != rec) {
		prev_rec = rec;
		rec = page_rec_get_next(rec);
	}

	page_cur_move_to_next(cursor);
	next_rec = cursor->rec;

	/* 3. Remove the record from the linked list of records */

	page_rec_set_next(prev_rec, next_rec);

	/* 4. If the deleted record is pointed to by a dir slot, update the
	record pointer in slot. In the following if-clause we assume that
	prev_rec is owned by the same slot, i.e., PAGE_DIR_SLOT_MIN_N_OWNED
	>= 2. */

#if PAGE_DIR_SLOT_MIN_N_OWNED < 2
# error "PAGE_DIR_SLOT_MIN_N_OWNED < 2"
#endif
	ut_ad(cur_n_owned > 1);

	if (current_rec == page_dir_slot_get_rec(cur_dir_slot)) {
		page_dir_slot_set_rec(cur_dir_slot, prev_rec);
	}

	/* 5. Update the number of owned records of the slot */

	page_dir_slot_set_n_owned(cur_dir_slot, page_zip, cur_n_owned - 1);

	/* 6. Free the memory occupied by the record */
	page_mem_free(page, page_zip, current_rec, offsets);
	page_header_set_field(page, page_zip, PAGE_N_RECS,
				(ulint)(page_get_n_recs(page) - 1));
	if (UNIV_LIKELY_NULL(page_zip)) {
		/* Clear the data bytes of the deleted record in order
		to improve the compression ratio of the page.  The fixed extra
		bytes of the record, which will be omitted from the
		stream compression algorithm, cannot be cleared, because
		page_mem_alloc() needs them in order to determine the size
		of the deleted record. */
		page_zip_clear_rec(page_zip, rec, index, offsets, mtr);
	}

	/* 7. Now we have decremented the number of owned records of the slot.
	If the number drops below PAGE_DIR_SLOT_MIN_N_OWNED, we balance the
	slots. */

	if (UNIV_UNLIKELY(cur_n_owned <= PAGE_DIR_SLOT_MIN_N_OWNED)) {
		page_dir_balance_slot(page, page_zip, cur_slot_no);
	}
}