Adding upstream version 1:10.11.6.upstream/1%10.11.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4666 insertions, 0 deletions

diff --git a/storage/innobase/page/page0zip.cc b/storage/innobase/page/page0zip.cc
new file mode 100644
index 00000000..89e6d149
--- /dev/null
+++ b/storage/innobase/page/page0zip.cc
@@ -0,0 +1,4666 @@
+/*****************************************************************************
+
+Copyright (c) 2005, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2012, Facebook Inc.
+Copyright (c) 2014, 2022, MariaDB Corporation.
+
+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, Fifth Floor, Boston, MA 02110-1335 USA
+
+*****************************************************************************/
+
+/**************************************************//**
+@file page/page0zip.cc
+Compressed page interface
+
+Created June 2005 by Marko Makela
+*******************************************************/
+
+#include "page0zip.h"
+#include "fsp0types.h"
+#include "page0page.h"
+#include "buf0checksum.h"
+#include "zlib.h"
+#include "span.h"
+
+using st_::span;
+
+#ifndef UNIV_INNOCHECKSUM
+#include "mtr0log.h"
+#include "dict0dict.h"
+#include "btr0cur.h"
+#include "log0recv.h"
+#include "row0row.h"
+#include "btr0sea.h"
+#include "dict0boot.h"
+#include "lock0lock.h"
+#include "srv0srv.h"
+#include "buf0lru.h"
+#include "srv0mon.h"
+
+#include <map>
+#include <algorithm>
+
+/** Statistics on compression, indexed by page_zip_des_t::ssize - 1 */
+page_zip_stat_t		page_zip_stat[PAGE_ZIP_SSIZE_MAX];
+/** Statistics on compression, indexed by index->id */
+page_zip_stat_per_index_t	page_zip_stat_per_index;
+
+/** Compression level to be used by zlib. Settable by user. */
+uint	page_zip_level;
+
+/* Please refer to ../include/page0zip.ic for a description of the
+compressed page format. */
+
+/* The infimum and supremum records are omitted from the compressed page.
+On compress, we compare that the records are there, and on uncompress we
+restore the records. */
+/** Extra bytes of an infimum record */
+static const byte infimum_extra[] = {
+	0x01,			/* info_bits=0, n_owned=1 */
+	0x00, 0x02		/* heap_no=0, status=2 */
+	/* ?, ?	*/		/* next=(first user rec, or supremum) */
+};
+/** Data bytes of an infimum record */
+static const byte infimum_data[] = {
+	0x69, 0x6e, 0x66, 0x69,
+	0x6d, 0x75, 0x6d, 0x00	/* "infimum\0" */
+};
+/** Extra bytes and data bytes of a supremum record */
+static const byte supremum_extra_data alignas(4) [] = {
+	/* 0x0?, */		/* info_bits=0, n_owned=1..8 */
+	0x00, 0x0b,		/* heap_no=1, status=3 */
+	0x00, 0x00,		/* next=0 */
+	0x73, 0x75, 0x70, 0x72,
+	0x65, 0x6d, 0x75, 0x6d	/* "supremum" */
+};
+
+/** Assert that a block of memory is filled with zero bytes.
+@param b in: memory block
+@param s in: size of the memory block, in bytes */
+#define ASSERT_ZERO(b, s) ut_ad(!memcmp(b, field_ref_zero, s))
+/** Assert that a BLOB pointer is filled with zero bytes.
+@param b in: BLOB pointer */
+#define ASSERT_ZERO_BLOB(b) ASSERT_ZERO(b, FIELD_REF_SIZE)
+
+/* Enable some extra debugging output.  This code can be enabled
+independently of any UNIV_ debugging conditions. */
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+# include <stdarg.h>
+MY_ATTRIBUTE((format (printf, 1, 2)))
+/**********************************************************************//**
+Report a failure to decompress or compress.
+@return number of characters printed */
+static
+int
+page_zip_fail_func(
+/*===============*/
+	const char*	fmt,	/*!< in: printf(3) format string */
+	...)			/*!< in: arguments corresponding to fmt */
+{
+	int	res;
+	va_list	ap;
+
+	ut_print_timestamp(stderr);
+	fputs("  InnoDB: ", stderr);
+	va_start(ap, fmt);
+	res = vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	return(res);
+}
+/** Wrapper for page_zip_fail_func()
+@param fmt_args in: printf(3) format string and arguments */
+# define page_zip_fail(fmt_args) page_zip_fail_func fmt_args
+#else /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+/** Dummy wrapper for page_zip_fail_func()
+@param fmt_args ignored: printf(3) format string and arguments */
+# define page_zip_fail(fmt_args) /* empty */
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+
+/**********************************************************************//**
+Determine the guaranteed free space on an empty page.
+@return minimum payload size on the page */
+ulint
+page_zip_empty_size(
+/*================*/
+	ulint	n_fields,	/*!< in: number of columns in the index */
+	ulint	zip_size)	/*!< in: compressed page size in bytes */
+{
+	ulint	size = zip_size
+		/* subtract the page header and the longest
+		uncompressed data needed for one record */
+		- (PAGE_DATA
+		   + PAGE_ZIP_CLUST_LEAF_SLOT_SIZE
+		   + 1/* encoded heap_no==2 in page_zip_write_rec() */
+		   + 1/* end of modification log */
+		   - REC_N_NEW_EXTRA_BYTES/* omitted bytes */)
+		/* subtract the space for page_zip_fields_encode() */
+		- compressBound(static_cast<uLong>(2 * (n_fields + 1)));
+	return(lint(size) > 0 ? size : 0);
+}
+
+/** Check whether a tuple is too big for compressed table
+@param[in]	index	dict index object
+@param[in]	entry	entry for the index
+@return	true if it's too big, otherwise false */
+bool
+page_zip_is_too_big(
+	const dict_index_t*	index,
+	const dtuple_t*		entry)
+{
+	const ulint zip_size = index->table->space->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(
+		index->n_fields, zip_size);
+	ulint	n_uniq = dict_index_get_n_unique_in_tree(index);
+
+	ut_ad(dict_table_is_comp(index->table));
+	ut_ad(zip_size);
+
+	if (free_space_zip == 0) {
+		return(true);
+	}
+
+	/* 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)) {
+		return(true);
+	}
+
+	return(false);
+}
+
+/*************************************************************//**
+Gets the number of elements in the dense page directory,
+including deleted records (the free list).
+@return number of elements in the dense page directory */
+UNIV_INLINE
+ulint
+page_zip_dir_elems(
+/*===============*/
+	const page_zip_des_t*	page_zip)	/*!< in: compressed page */
+{
+	/* Exclude the page infimum and supremum from the record count. */
+	return ulint(page_dir_get_n_heap(page_zip->data))
+		- PAGE_HEAP_NO_USER_LOW;
+}
+
+/*************************************************************//**
+Gets the size of the compressed page trailer (the dense page directory),
+including deleted records (the free list).
+@return length of dense page directory, in bytes */
+UNIV_INLINE
+ulint
+page_zip_dir_size(
+/*==============*/
+	const page_zip_des_t*	page_zip)	/*!< in: compressed page */
+{
+	return(PAGE_ZIP_DIR_SLOT_SIZE * page_zip_dir_elems(page_zip));
+}
+
+/*************************************************************//**
+Gets an offset to the compressed page trailer (the dense page directory),
+including deleted records (the free list).
+@return offset of the dense page directory */
+UNIV_INLINE
+ulint
+page_zip_dir_start_offs(
+/*====================*/
+	const page_zip_des_t*	page_zip,	/*!< in: compressed page */
+	ulint			n_dense)	/*!< in: directory size */
+{
+	ut_ad(n_dense * PAGE_ZIP_DIR_SLOT_SIZE < page_zip_get_size(page_zip));
+
+	return(page_zip_get_size(page_zip) - n_dense * PAGE_ZIP_DIR_SLOT_SIZE);
+}
+
+/*************************************************************//**
+Gets a pointer to the compressed page trailer (the dense page directory),
+including deleted records (the free list).
+@param[in] page_zip compressed page
+@param[in] n_dense number of entries in the directory
+@return pointer to the dense page directory */
+#define page_zip_dir_start_low(page_zip, n_dense)			\
+	((page_zip)->data + page_zip_dir_start_offs(page_zip, n_dense))
+/*************************************************************//**
+Gets a pointer to the compressed page trailer (the dense page directory),
+including deleted records (the free list).
+@param[in] page_zip compressed page
+@return pointer to the dense page directory */
+#define page_zip_dir_start(page_zip)					\
+	page_zip_dir_start_low(page_zip, page_zip_dir_elems(page_zip))
+
+/*************************************************************//**
+Gets the size of the compressed page trailer (the dense page directory),
+only including user records (excluding the free list).
+@return length of dense page directory comprising existing records, in bytes */
+UNIV_INLINE
+ulint
+page_zip_dir_user_size(
+/*===================*/
+	const page_zip_des_t*	page_zip)	/*!< in: compressed page */
+{
+	ulint	size = PAGE_ZIP_DIR_SLOT_SIZE
+		* ulint(page_get_n_recs(page_zip->data));
+	ut_ad(size <= page_zip_dir_size(page_zip));
+	return(size);
+}
+
+/*************************************************************//**
+Find the slot of the given record in the dense page directory.
+@return dense directory slot, or NULL if record not found */
+UNIV_INLINE
+byte*
+page_zip_dir_find_low(
+/*==================*/
+	byte*	slot,			/*!< in: start of records */
+	byte*	end,			/*!< in: end of records */
+	ulint	offset)			/*!< in: offset of user record */
+{
+	ut_ad(slot <= end);
+
+	for (; slot < end; slot += PAGE_ZIP_DIR_SLOT_SIZE) {
+		if ((mach_read_from_2(slot) & PAGE_ZIP_DIR_SLOT_MASK)
+		    == offset) {
+			return(slot);
+		}
+	}
+
+	return(NULL);
+}
+
+/*************************************************************//**
+Find the slot of the given non-free record in the dense page directory.
+@return dense directory slot, or NULL if record not found */
+UNIV_INLINE
+byte*
+page_zip_dir_find(
+/*==============*/
+	page_zip_des_t*	page_zip,		/*!< in: compressed page */
+	ulint		offset)			/*!< in: offset of user record */
+{
+	byte*	end	= page_zip->data + page_zip_get_size(page_zip);
+
+	ut_ad(page_zip_simple_validate(page_zip));
+
+	return(page_zip_dir_find_low(end - page_zip_dir_user_size(page_zip),
+				     end,
+				     offset));
+}
+
+/*************************************************************//**
+Find the slot of the given free record in the dense page directory.
+@return dense directory slot, or NULL if record not found */
+UNIV_INLINE
+byte*
+page_zip_dir_find_free(
+/*===================*/
+	page_zip_des_t*	page_zip,		/*!< in: compressed page */
+	ulint		offset)			/*!< in: offset of user record */
+{
+	byte*	end	= page_zip->data + page_zip_get_size(page_zip);
+
+	ut_ad(page_zip_simple_validate(page_zip));
+
+	return(page_zip_dir_find_low(end - page_zip_dir_size(page_zip),
+				     end - page_zip_dir_user_size(page_zip),
+				     offset));
+}
+
+/*************************************************************//**
+Read a given slot in the dense page directory.
+@return record offset on the uncompressed page, possibly ORed with
+PAGE_ZIP_DIR_SLOT_DEL or PAGE_ZIP_DIR_SLOT_OWNED */
+UNIV_INLINE
+ulint
+page_zip_dir_get(
+/*=============*/
+	const page_zip_des_t*	page_zip,	/*!< in: compressed page */
+	ulint			slot)		/*!< in: slot
+						(0=first user record) */
+{
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(slot < page_zip_dir_size(page_zip) / PAGE_ZIP_DIR_SLOT_SIZE);
+	return(mach_read_from_2(page_zip->data + page_zip_get_size(page_zip)
+				- PAGE_ZIP_DIR_SLOT_SIZE * (slot + 1)));
+}
+
+/** Write a byte string to a ROW_FORMAT=COMPRESSED page.
+@param[in]      b       ROW_FORMAT=COMPRESSED index page
+@param[in]      offset  byte offset from b.zip.data
+@param[in]      len     length of the data to write */
+inline void mtr_t::zmemcpy(const buf_block_t &b, ulint offset, ulint len)
+{
+  ut_ad(fil_page_get_type(b.page.zip.data) == FIL_PAGE_INDEX ||
+        fil_page_get_type(b.page.zip.data) == FIL_PAGE_RTREE);
+  ut_ad(page_zip_simple_validate(&b.page.zip));
+  ut_ad(offset + len <= page_zip_get_size(&b.page.zip));
+
+  memcpy_low(b, static_cast<uint16_t>(offset), &b.page.zip.data[offset], len);
+  m_last_offset= static_cast<uint16_t>(offset + len);
+}
+
+/** Write a byte string to a ROW_FORMAT=COMPRESSED page.
+@param[in]      b       ROW_FORMAT=COMPRESSED index page
+@param[in]      dest    destination within b.zip.data
+@param[in]      str     the data to write
+@param[in]      len     length of the data to write
+@tparam w       write request type */
+template<mtr_t::write_type w>
+inline void mtr_t::zmemcpy(const buf_block_t &b, void *dest, const void *str,
+                           ulint len)
+{
+  byte *d= static_cast<byte*>(dest);
+  const byte *s= static_cast<const byte*>(str);
+  ut_ad(d >= b.page.zip.data + FIL_PAGE_OFFSET);
+  if (w != FORCED)
+  {
+    ut_ad(len);
+    const byte *const end= d + len;
+    while (*d++ == *s++)
+    {
+      if (d == end)
+      {
+        ut_ad(w == MAYBE_NOP);
+        return;
+      }
+    }
+    s--;
+    d--;
+    len= static_cast<ulint>(end - d);
+  }
+  ::memcpy(d, s, len);
+  zmemcpy(b, d - b.page.zip.data, len);
+}
+
+/** Write redo log for compressing a ROW_FORMAT=COMPRESSED index page.
+@param[in,out]	block	ROW_FORMAT=COMPRESSED index page
+@param[in]	index	the index that the block belongs to
+@param[in,out]	mtr	mini-transaction */
+static void page_zip_compress_write_log(buf_block_t *block,
+                                        dict_index_t *index, mtr_t *mtr)
+{
+  ut_ad(!index->is_ibuf());
+
+  if (!mtr->is_logged())
+    return;
+
+  const page_t *page= block->page.frame;
+  const page_zip_des_t *page_zip= &block->page.zip;
+  /* Read the number of user records. */
+  ulint trailer_size= ulint(page_dir_get_n_heap(page_zip->data)) -
+    PAGE_HEAP_NO_USER_LOW;
+  /* Multiply by uncompressed of size stored per record */
+  if (!page_is_leaf(page))
+    trailer_size*= PAGE_ZIP_DIR_SLOT_SIZE + REC_NODE_PTR_SIZE;
+  else if (index->is_clust())
+    trailer_size*= PAGE_ZIP_DIR_SLOT_SIZE + DATA_TRX_ID_LEN +
+      DATA_ROLL_PTR_LEN;
+  else
+    trailer_size*= PAGE_ZIP_DIR_SLOT_SIZE;
+  /* Add the space occupied by BLOB pointers. */
+  trailer_size+= page_zip->n_blobs * BTR_EXTERN_FIELD_REF_SIZE;
+  ut_a(page_zip->m_end > PAGE_DATA);
+  compile_time_assert(FIL_PAGE_DATA <= PAGE_DATA);
+  ut_a(page_zip->m_end + trailer_size <= page_zip_get_size(page_zip));
+
+  mtr->init(block);
+  mtr->zmemcpy(*block, FIL_PAGE_PREV, page_zip->m_end - FIL_PAGE_PREV);
+
+  if (trailer_size)
+    mtr->zmemcpy(*block, page_zip_get_size(page_zip) - trailer_size,
+                 trailer_size);
+}
+
+/******************************************************//**
+Determine how many externally stored columns are contained
+in existing records with smaller heap_no than rec. */
+static
+ulint
+page_zip_get_n_prev_extern(
+/*=======================*/
+	const page_zip_des_t*	page_zip,/*!< in: dense page directory on
+					compressed page */
+	const rec_t*		rec,	/*!< in: compact physical record
+					on a B-tree leaf page */
+	const dict_index_t*	index)	/*!< in: record descriptor */
+{
+	const page_t*	page	= page_align(rec);
+	ulint		n_ext	= 0;
+	ulint		i;
+	ulint		left;
+	ulint		heap_no;
+	ulint		n_recs	= page_get_n_recs(page_zip->data);
+
+	ut_ad(page_is_leaf(page));
+	ut_ad(page_is_comp(page));
+	ut_ad(dict_table_is_comp(index->table));
+	ut_ad(dict_index_is_clust(index));
+	ut_ad(!dict_index_is_ibuf(index));
+
+	heap_no = rec_get_heap_no_new(rec);
+	ut_ad(heap_no >= PAGE_HEAP_NO_USER_LOW);
+	left = heap_no - PAGE_HEAP_NO_USER_LOW;
+	if (UNIV_UNLIKELY(!left)) {
+		return(0);
+	}
+
+	for (i = 0; i < n_recs; i++) {
+		const rec_t*	r	= page + (page_zip_dir_get(page_zip, i)
+						  & PAGE_ZIP_DIR_SLOT_MASK);
+
+		if (rec_get_heap_no_new(r) < heap_no) {
+			n_ext += rec_get_n_extern_new(r, index,
+						      ULINT_UNDEFINED);
+			if (!--left) {
+				break;
+			}
+		}
+	}
+
+	return(n_ext);
+}
+
+/**********************************************************************//**
+Encode the length of a fixed-length column.
+@return buf + length of encoded val */
+static
+byte*
+page_zip_fixed_field_encode(
+/*========================*/
+	byte*	buf,	/*!< in: pointer to buffer where to write */
+	ulint	val)	/*!< in: value to write */
+{
+	ut_ad(val >= 2);
+
+	if (UNIV_LIKELY(val < 126)) {
+		/*
+		0 = nullable variable field of at most 255 bytes length;
+		1 = not null variable field of at most 255 bytes length;
+		126 = nullable variable field with maximum length >255;
+		127 = not null variable field with maximum length >255
+		*/
+		*buf++ = (byte) val;
+	} else {
+		*buf++ = (byte) (0x80 | val >> 8);
+		*buf++ = (byte) val;
+	}
+
+	return(buf);
+}
+
+/**********************************************************************//**
+Write the index information for the compressed page.
+@return used size of buf */
+ulint
+page_zip_fields_encode(
+/*===================*/
+	ulint			n,	/*!< in: number of fields
+					to compress */
+	const dict_index_t*	index,	/*!< in: index comprising
+					at least n fields */
+	ulint			trx_id_pos,
+					/*!< in: position of the trx_id column
+					in the index, or ULINT_UNDEFINED if
+					this is a non-leaf page */
+	byte*			buf)	/*!< out: buffer of (n + 1) * 2 bytes */
+{
+	const byte*	buf_start	= buf;
+	ulint		i;
+	ulint		col;
+	ulint		trx_id_col	= 0;
+	/* sum of lengths of preceding non-nullable fixed fields, or 0 */
+	ulint		fixed_sum	= 0;
+
+	ut_ad(trx_id_pos == ULINT_UNDEFINED || trx_id_pos < n);
+
+	for (i = col = 0; i < n; i++) {
+		dict_field_t*	field = dict_index_get_nth_field(index, i);
+		ulint		val;
+
+		if (dict_field_get_col(field)->prtype & DATA_NOT_NULL) {
+			val = 1; /* set the "not nullable" flag */
+		} else {
+			val = 0; /* nullable field */
+		}
+
+		if (!field->fixed_len) {
+			/* variable-length field */
+			const dict_col_t*	column
+				= dict_field_get_col(field);
+
+			if (DATA_BIG_COL(column)) {
+				val |= 0x7e; /* max > 255 bytes */
+			}
+
+			if (fixed_sum) {
+				/* write out the length of any
+				preceding non-nullable fields */
+				buf = page_zip_fixed_field_encode(
+					buf, fixed_sum << 1 | 1);
+				fixed_sum = 0;
+				col++;
+			}
+
+			*buf++ = (byte) val;
+			col++;
+		} else if (val) {
+			/* fixed-length non-nullable field */
+
+			if (fixed_sum && UNIV_UNLIKELY
+			    (fixed_sum + field->fixed_len
+			     > DICT_MAX_FIXED_COL_LEN)) {
+				/* Write out the length of the
+				preceding non-nullable fields,
+				to avoid exceeding the maximum
+				length of a fixed-length column. */
+				buf = page_zip_fixed_field_encode(
+					buf, fixed_sum << 1 | 1);
+				fixed_sum = 0;
+				col++;
+			}
+
+			if (i && UNIV_UNLIKELY(i == trx_id_pos)) {
+				if (fixed_sum) {
+					/* Write out the length of any
+					preceding non-nullable fields,
+					and start a new trx_id column. */
+					buf = page_zip_fixed_field_encode(
+						buf, fixed_sum << 1 | 1);
+					col++;
+				}
+
+				trx_id_col = col;
+				fixed_sum = field->fixed_len;
+			} else {
+				/* add to the sum */
+				fixed_sum += field->fixed_len;
+			}
+		} else {
+			/* fixed-length nullable field */
+
+			if (fixed_sum) {
+				/* write out the length of any
+				preceding non-nullable fields */
+				buf = page_zip_fixed_field_encode(
+					buf, fixed_sum << 1 | 1);
+				fixed_sum = 0;
+				col++;
+			}
+
+			buf = page_zip_fixed_field_encode(
+				buf, ulint(field->fixed_len) << 1);
+			col++;
+		}
+	}
+
+	if (fixed_sum) {
+		/* Write out the lengths of last fixed-length columns. */
+		buf = page_zip_fixed_field_encode(buf, fixed_sum << 1 | 1);
+	}
+
+	if (trx_id_pos != ULINT_UNDEFINED) {
+		/* Write out the position of the trx_id column */
+		i = trx_id_col;
+	} else {
+		/* Write out the number of nullable fields */
+		i = index->n_nullable;
+	}
+
+	if (i < 128) {
+		*buf++ = (byte) i;
+	} else {
+		*buf++ = (byte) (0x80 | i >> 8);
+		*buf++ = (byte) i;
+	}
+
+	ut_ad((ulint) (buf - buf_start) <= (n + 2) * 2);
+	return((ulint) (buf - buf_start));
+}
+
+/**********************************************************************//**
+Populate the dense page directory from the sparse directory. */
+static
+void
+page_zip_dir_encode(
+/*================*/
+	const page_t*	page,	/*!< in: compact page */
+	byte*		buf,	/*!< in: pointer to dense page directory[-1];
+				out: dense directory on compressed page */
+	const rec_t**	recs)	/*!< in: pointer to an array of 0, or NULL;
+				out: dense page directory sorted by ascending
+				address (and heap_no) */
+{
+	const byte*	rec;
+	ulint		status;
+	ulint		min_mark;
+	ulint		heap_no;
+	ulint		i;
+	ulint		n_heap;
+	ulint		offs;
+
+	min_mark = 0;
+
+	if (page_is_leaf(page)) {
+		status = REC_STATUS_ORDINARY;
+	} else {
+		status = REC_STATUS_NODE_PTR;
+		if (UNIV_UNLIKELY(!page_has_prev(page))) {
+			min_mark = REC_INFO_MIN_REC_FLAG;
+		}
+	}
+
+	n_heap = page_dir_get_n_heap(page);
+
+	/* Traverse the list of stored records in the collation order,
+	starting from the first user record. */
+
+	rec = page + PAGE_NEW_INFIMUM;
+
+	i = 0;
+
+	for (;;) {
+		ulint	info_bits;
+		offs = rec_get_next_offs(rec, TRUE);
+		if (UNIV_UNLIKELY(offs == PAGE_NEW_SUPREMUM)) {
+			break;
+		}
+		rec = page + offs;
+		heap_no = rec_get_heap_no_new(rec);
+		ut_a(heap_no >= PAGE_HEAP_NO_USER_LOW);
+		ut_a(heap_no < n_heap);
+		ut_a(offs < srv_page_size - PAGE_DIR);
+		ut_a(offs >= PAGE_ZIP_START);
+		compile_time_assert(!(PAGE_ZIP_DIR_SLOT_MASK
+				      & (PAGE_ZIP_DIR_SLOT_MASK + 1)));
+		compile_time_assert(PAGE_ZIP_DIR_SLOT_MASK
+				    >= UNIV_ZIP_SIZE_MAX - 1);
+
+		if (UNIV_UNLIKELY(rec_get_n_owned_new(rec) != 0)) {
+			offs |= PAGE_ZIP_DIR_SLOT_OWNED;
+		}
+
+		info_bits = rec_get_info_bits(rec, TRUE);
+		if (info_bits & REC_INFO_DELETED_FLAG) {
+			info_bits &= ~REC_INFO_DELETED_FLAG;
+			offs |= PAGE_ZIP_DIR_SLOT_DEL;
+		}
+		ut_a(info_bits == min_mark);
+		/* Only the smallest user record can have
+		REC_INFO_MIN_REC_FLAG set. */
+		min_mark = 0;
+
+		mach_write_to_2(buf - PAGE_ZIP_DIR_SLOT_SIZE * ++i, offs);
+
+		if (UNIV_LIKELY_NULL(recs)) {
+			/* Ensure that each heap_no occurs at most once. */
+			ut_a(!recs[heap_no - PAGE_HEAP_NO_USER_LOW]);
+			/* exclude infimum and supremum */
+			recs[heap_no - PAGE_HEAP_NO_USER_LOW] = rec;
+		}
+
+		ut_a(ulint(rec_get_status(rec)) == status);
+	}
+
+	offs = page_header_get_field(page, PAGE_FREE);
+
+	/* Traverse the free list (of deleted records). */
+	while (offs) {
+		ut_ad(!(offs & ~PAGE_ZIP_DIR_SLOT_MASK));
+		rec = page + offs;
+
+		heap_no = rec_get_heap_no_new(rec);
+		ut_a(heap_no >= PAGE_HEAP_NO_USER_LOW);
+		ut_a(heap_no < n_heap);
+
+		ut_a(!rec[-REC_N_NEW_EXTRA_BYTES]); /* info_bits and n_owned */
+		ut_a(ulint(rec_get_status(rec)) == status);
+
+		mach_write_to_2(buf - PAGE_ZIP_DIR_SLOT_SIZE * ++i, offs);
+
+		if (UNIV_LIKELY_NULL(recs)) {
+			/* Ensure that each heap_no occurs at most once. */
+			ut_a(!recs[heap_no - PAGE_HEAP_NO_USER_LOW]);
+			/* exclude infimum and supremum */
+			recs[heap_no - PAGE_HEAP_NO_USER_LOW] = rec;
+		}
+
+		offs = rec_get_next_offs(rec, TRUE);
+	}
+
+	/* Ensure that each heap no occurs at least once. */
+	ut_a(i + PAGE_HEAP_NO_USER_LOW == n_heap);
+}
+
+extern "C" {
+
+/**********************************************************************//**
+Allocate memory for zlib. */
+static
+void*
+page_zip_zalloc(
+/*============*/
+	void*	opaque,	/*!< in/out: memory heap */
+	uInt	items,	/*!< in: number of items to allocate */
+	uInt	size)	/*!< in: size of an item in bytes */
+{
+	return(mem_heap_zalloc(static_cast<mem_heap_t*>(opaque), items * size));
+}
+
+/**********************************************************************//**
+Deallocate memory for zlib. */
+static
+void
+page_zip_free(
+/*==========*/
+	void*	opaque MY_ATTRIBUTE((unused)),	/*!< in: memory heap */
+	void*	address MY_ATTRIBUTE((unused)))/*!< in: object to free */
+{
+}
+
+} /* extern "C" */
+
+/**********************************************************************//**
+Configure the zlib allocator to use the given memory heap. */
+void
+page_zip_set_alloc(
+/*===============*/
+	void*		stream,		/*!< in/out: zlib stream */
+	mem_heap_t*	heap)		/*!< in: memory heap to use */
+{
+	z_stream*	strm = static_cast<z_stream*>(stream);
+
+	strm->zalloc = page_zip_zalloc;
+	strm->zfree = page_zip_free;
+	strm->opaque = heap;
+}
+
+#if 0 || defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+/** Symbol for enabling compression and decompression diagnostics */
+# define PAGE_ZIP_COMPRESS_DBG
+#endif
+
+#ifdef PAGE_ZIP_COMPRESS_DBG
+/** Set this variable in a debugger to enable
+excessive logging in page_zip_compress(). */
+static bool	page_zip_compress_dbg;
+/** Set this variable in a debugger to enable
+binary logging of the data passed to deflate().
+When this variable is nonzero, it will act
+as a log file name generator. */
+static unsigned	page_zip_compress_log;
+
+/**********************************************************************//**
+Wrapper for deflate().  Log the operation if page_zip_compress_dbg is set.
+@return deflate() status: Z_OK, Z_BUF_ERROR, ... */
+static
+int
+page_zip_compress_deflate(
+/*======================*/
+	FILE*		logfile,/*!< in: log file, or NULL */
+	z_streamp	strm,	/*!< in/out: compressed stream for deflate() */
+	int		flush)	/*!< in: deflate() flushing method */
+{
+	int	status;
+	if (UNIV_UNLIKELY(page_zip_compress_dbg)) {
+		ut_print_buf(stderr, strm->next_in, strm->avail_in);
+	}
+	if (UNIV_LIKELY_NULL(logfile)) {
+		if (fwrite(strm->next_in, 1, strm->avail_in, logfile)
+		    != strm->avail_in) {
+			perror("fwrite");
+		}
+	}
+	status = deflate(strm, flush);
+	if (UNIV_UNLIKELY(page_zip_compress_dbg)) {
+		fprintf(stderr, " -> %d\n", status);
+	}
+	return(status);
+}
+
+/* Redefine deflate(). */
+# undef deflate
+/** Debug wrapper for the zlib compression routine deflate().
+Log the operation if page_zip_compress_dbg is set.
+@param strm in/out: compressed stream
+@param flush in: flushing method
+@return deflate() status: Z_OK, Z_BUF_ERROR, ... */
+# define deflate(strm, flush) page_zip_compress_deflate(logfile, strm, flush)
+/** Declaration of the logfile parameter */
+# define FILE_LOGFILE FILE* logfile,
+/** The logfile parameter */
+# define LOGFILE logfile,
+#else /* PAGE_ZIP_COMPRESS_DBG */
+/** Empty declaration of the logfile parameter */
+# define FILE_LOGFILE
+/** Missing logfile parameter */
+# define LOGFILE
+#endif /* PAGE_ZIP_COMPRESS_DBG */
+
+/**********************************************************************//**
+Compress the records of a node pointer page.
+@return Z_OK, or a zlib error code */
+static
+int
+page_zip_compress_node_ptrs(
+/*========================*/
+	FILE_LOGFILE
+	z_stream*	c_stream,	/*!< in/out: compressed page stream */
+	const rec_t**	recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense,	/*!< in: size of recs[] */
+	dict_index_t*	index,		/*!< in: the index of the page */
+	byte*		storage,	/*!< in: end of dense page directory */
+	mem_heap_t*	heap)		/*!< in: temporary memory heap */
+{
+	int	err	= Z_OK;
+	rec_offs* offsets = NULL;
+
+	do {
+		const rec_t*	rec = *recs++;
+
+		offsets = rec_get_offsets(rec, index, offsets, 0,
+					  ULINT_UNDEFINED, &heap);
+		/* Only leaf nodes may contain externally stored columns. */
+		ut_ad(!rec_offs_any_extern(offsets));
+
+		MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+		MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+				  rec_offs_extra_size(offsets));
+
+		/* Compress the extra bytes. */
+		c_stream->avail_in = static_cast<uInt>(
+			rec - REC_N_NEW_EXTRA_BYTES - c_stream->next_in);
+
+		if (c_stream->avail_in) {
+			err = deflate(c_stream, Z_NO_FLUSH);
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+				break;
+			}
+		}
+		ut_ad(!c_stream->avail_in);
+
+		/* Compress the data bytes, except node_ptr. */
+		c_stream->next_in = (byte*) rec;
+		c_stream->avail_in = static_cast<uInt>(
+			rec_offs_data_size(offsets) - REC_NODE_PTR_SIZE);
+
+		if (c_stream->avail_in) {
+			err = deflate(c_stream, Z_NO_FLUSH);
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+				break;
+			}
+		}
+
+		ut_ad(!c_stream->avail_in);
+
+		memcpy(storage - REC_NODE_PTR_SIZE
+		       * (rec_get_heap_no_new(rec) - 1),
+		       c_stream->next_in, REC_NODE_PTR_SIZE);
+		c_stream->next_in += REC_NODE_PTR_SIZE;
+	} while (--n_dense);
+
+	return(err);
+}
+
+/**********************************************************************//**
+Compress the records of a leaf node of a secondary index.
+@return Z_OK, or a zlib error code */
+static
+int
+page_zip_compress_sec(
+/*==================*/
+	FILE_LOGFILE
+	z_stream*	c_stream,	/*!< in/out: compressed page stream */
+	const rec_t**	recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense)	/*!< in: size of recs[] */
+{
+	int		err	= Z_OK;
+
+	ut_ad(n_dense > 0);
+
+	do {
+		const rec_t*	rec = *recs++;
+
+		/* Compress everything up to this record. */
+		c_stream->avail_in = static_cast<uInt>(
+			rec - REC_N_NEW_EXTRA_BYTES
+			- c_stream->next_in);
+
+		if (UNIV_LIKELY(c_stream->avail_in != 0)) {
+			MEM_CHECK_DEFINED(c_stream->next_in,
+					  c_stream->avail_in);
+			err = deflate(c_stream, Z_NO_FLUSH);
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+				break;
+			}
+		}
+
+		ut_ad(!c_stream->avail_in);
+		ut_ad(c_stream->next_in == rec - REC_N_NEW_EXTRA_BYTES);
+
+		/* Skip the REC_N_NEW_EXTRA_BYTES. */
+
+		c_stream->next_in = (byte*) rec;
+	} while (--n_dense);
+
+	return(err);
+}
+
+/**********************************************************************//**
+Compress a record of a leaf node of a clustered index that contains
+externally stored columns.
+@return Z_OK, or a zlib error code */
+static
+int
+page_zip_compress_clust_ext(
+/*========================*/
+	FILE_LOGFILE
+	z_stream*	c_stream,	/*!< in/out: compressed page stream */
+	const rec_t*	rec,		/*!< in: record */
+	const rec_offs*	offsets,	/*!< in: rec_get_offsets(rec) */
+	ulint		trx_id_col,	/*!< in: position of of DB_TRX_ID */
+	byte*		deleted,	/*!< in: dense directory entry pointing
+					to the head of the free list */
+	byte*		storage,	/*!< in: end of dense page directory */
+	byte**		externs,	/*!< in/out: pointer to the next
+					available BLOB pointer */
+	ulint*		n_blobs)	/*!< in/out: number of
+					externally stored columns */
+{
+	int	err;
+	ulint	i;
+
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+
+	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
+		ulint		len;
+		const byte*	src;
+
+		if (UNIV_UNLIKELY(i == trx_id_col)) {
+			ut_ad(!rec_offs_nth_extern(offsets, i));
+			/* Store trx_id and roll_ptr
+			in uncompressed form. */
+			src = rec_get_nth_field(rec, offsets, i, &len);
+			ut_ad(src + DATA_TRX_ID_LEN
+			      == rec_get_nth_field(rec, offsets,
+						   i + 1, &len));
+			ut_ad(len == DATA_ROLL_PTR_LEN);
+
+			/* Compress any preceding bytes. */
+			c_stream->avail_in = static_cast<uInt>(
+				src - c_stream->next_in);
+
+			if (c_stream->avail_in) {
+				err = deflate(c_stream, Z_NO_FLUSH);
+				if (UNIV_UNLIKELY(err != Z_OK)) {
+
+					return(err);
+				}
+			}
+
+			ut_ad(!c_stream->avail_in);
+			ut_ad(c_stream->next_in == src);
+
+			memcpy(storage
+			       - (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN)
+			       * (rec_get_heap_no_new(rec) - 1),
+			       c_stream->next_in,
+			       DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+			c_stream->next_in
+				+= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+
+			/* Skip also roll_ptr */
+			i++;
+		} else if (rec_offs_nth_extern(offsets, i)) {
+			src = rec_get_nth_field(rec, offsets, i, &len);
+			ut_ad(len >= BTR_EXTERN_FIELD_REF_SIZE);
+			src += len - BTR_EXTERN_FIELD_REF_SIZE;
+
+			c_stream->avail_in = static_cast<uInt>(
+				src - c_stream->next_in);
+			if (UNIV_LIKELY(c_stream->avail_in != 0)) {
+				err = deflate(c_stream, Z_NO_FLUSH);
+				if (UNIV_UNLIKELY(err != Z_OK)) {
+
+					return(err);
+				}
+			}
+
+			ut_ad(!c_stream->avail_in);
+			ut_ad(c_stream->next_in == src);
+
+			/* Reserve space for the data at
+			the end of the space reserved for
+			the compressed data and the page
+			modification log. */
+
+			if (UNIV_UNLIKELY
+			    (c_stream->avail_out
+			     <= BTR_EXTERN_FIELD_REF_SIZE)) {
+				/* out of space */
+				return(Z_BUF_ERROR);
+			}
+
+			ut_ad(*externs == c_stream->next_out
+			      + c_stream->avail_out
+			      + 1/* end of modif. log */);
+
+			c_stream->next_in
+				+= BTR_EXTERN_FIELD_REF_SIZE;
+
+			/* Skip deleted records. */
+			if (UNIV_LIKELY_NULL
+			    (page_zip_dir_find_low(
+				    storage, deleted,
+				    page_offset(rec)))) {
+				continue;
+			}
+
+			(*n_blobs)++;
+			c_stream->avail_out
+				-= BTR_EXTERN_FIELD_REF_SIZE;
+			*externs -= BTR_EXTERN_FIELD_REF_SIZE;
+
+			/* Copy the BLOB pointer */
+			memcpy(*externs, c_stream->next_in
+			       - BTR_EXTERN_FIELD_REF_SIZE,
+			       BTR_EXTERN_FIELD_REF_SIZE);
+		}
+	}
+
+	return(Z_OK);
+}
+
+/**********************************************************************//**
+Compress the records of a leaf node of a clustered index.
+@return Z_OK, or a zlib error code */
+static
+int
+page_zip_compress_clust(
+/*====================*/
+	FILE_LOGFILE
+	z_stream*	c_stream,	/*!< in/out: compressed page stream */
+	const rec_t**	recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense,	/*!< in: size of recs[] */
+	dict_index_t*	index,		/*!< in: the index of the page */
+	ulint*		n_blobs,	/*!< in: 0; out: number of
+					externally stored columns */
+	ulint		trx_id_col,	/*!< index of the trx_id column */
+	byte*		deleted,	/*!< in: dense directory entry pointing
+					to the head of the free list */
+	byte*		storage,	/*!< in: end of dense page directory */
+	mem_heap_t*	heap)		/*!< in: temporary memory heap */
+{
+	int	err		= Z_OK;
+	rec_offs* offsets		= NULL;
+	/* BTR_EXTERN_FIELD_REF storage */
+	byte*	externs		= storage - n_dense
+		* (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+	ut_ad(*n_blobs == 0);
+
+	do {
+		const rec_t*	rec = *recs++;
+
+		offsets = rec_get_offsets(rec, index, offsets, index->n_fields,
+					  ULINT_UNDEFINED, &heap);
+		ut_ad(rec_offs_n_fields(offsets)
+		      == dict_index_get_n_fields(index));
+		MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+		MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+				  rec_offs_extra_size(offsets));
+
+		/* Compress the extra bytes. */
+		c_stream->avail_in = static_cast<uInt>(
+			rec - REC_N_NEW_EXTRA_BYTES
+			- c_stream->next_in);
+
+		if (c_stream->avail_in) {
+			err = deflate(c_stream, Z_NO_FLUSH);
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+
+				goto func_exit;
+			}
+		}
+		ut_ad(!c_stream->avail_in);
+		ut_ad(c_stream->next_in == rec - REC_N_NEW_EXTRA_BYTES);
+
+		/* Compress the data bytes. */
+
+		c_stream->next_in = (byte*) rec;
+
+		/* Check if there are any externally stored columns.
+		For each externally stored column, store the
+		BTR_EXTERN_FIELD_REF separately. */
+		if (rec_offs_any_extern(offsets)) {
+			ut_ad(dict_index_is_clust(index));
+
+			err = page_zip_compress_clust_ext(
+				LOGFILE
+				c_stream, rec, offsets, trx_id_col,
+				deleted, storage, &externs, n_blobs);
+
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+
+				goto func_exit;
+			}
+		} else {
+			ulint		len;
+			const byte*	src;
+
+			/* Store trx_id and roll_ptr in uncompressed form. */
+			src = rec_get_nth_field(rec, offsets,
+						trx_id_col, &len);
+			ut_ad(src + DATA_TRX_ID_LEN
+			      == rec_get_nth_field(rec, offsets,
+						   trx_id_col + 1, &len));
+			ut_ad(len == DATA_ROLL_PTR_LEN);
+			MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+			MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+					  rec_offs_extra_size(offsets));
+
+			/* Compress any preceding bytes. */
+			c_stream->avail_in = static_cast<uInt>(
+				src - c_stream->next_in);
+
+			if (c_stream->avail_in) {
+				err = deflate(c_stream, Z_NO_FLUSH);
+				if (UNIV_UNLIKELY(err != Z_OK)) {
+
+					return(err);
+				}
+			}
+
+			ut_ad(!c_stream->avail_in);
+			ut_ad(c_stream->next_in == src);
+
+			memcpy(storage
+			       - (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN)
+			       * (rec_get_heap_no_new(rec) - 1),
+			       c_stream->next_in,
+			       DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+			c_stream->next_in
+				+= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+
+			/* Skip also roll_ptr */
+			ut_ad(trx_id_col + 1 < rec_offs_n_fields(offsets));
+		}
+
+		/* Compress the last bytes of the record. */
+		c_stream->avail_in = static_cast<uInt>(
+			rec + rec_offs_data_size(offsets) - c_stream->next_in);
+
+		if (c_stream->avail_in) {
+			err = deflate(c_stream, Z_NO_FLUSH);
+			if (UNIV_UNLIKELY(err != Z_OK)) {
+
+				goto func_exit;
+			}
+		}
+		ut_ad(!c_stream->avail_in);
+	} while (--n_dense);
+
+func_exit:
+	return(err);}
+
+/** Attempt to compress a ROW_FORMAT=COMPRESSED page.
+@retval true on success
+@retval false on failure; block->page.zip will be left intact. */
+bool
+page_zip_compress(
+	buf_block_t*		block,	/*!< in/out: buffer block */
+	dict_index_t*		index,	/*!< in: index of the B-tree node */
+	ulint			level,	/*!< in: commpression level */
+	mtr_t*			mtr)	/*!< in/out: mini-transaction */
+{
+	z_stream		c_stream;
+	int			err;
+	byte*			fields;		/*!< index field information */
+	byte*			buf;		/*!< compressed payload of the
+						page */
+	byte*			buf_end;	/* end of buf */
+	ulint			n_dense;
+	ulint			slot_size;	/* amount of uncompressed bytes
+						per record */
+	const rec_t**		recs;		/*!< dense page directory,
+						sorted by address */
+	mem_heap_t*		heap;
+	ulint			trx_id_col = ULINT_UNDEFINED;
+	ulint			n_blobs	= 0;
+	byte*			storage;	/* storage of uncompressed
+						columns */
+	const ulonglong		ns = my_interval_timer();
+#ifdef PAGE_ZIP_COMPRESS_DBG
+	FILE*			logfile = NULL;
+#endif
+	/* A local copy of srv_cmp_per_index_enabled to avoid reading that
+	variable multiple times in this function since it can be changed at
+	anytime. */
+	my_bool			cmp_per_index_enabled;
+	cmp_per_index_enabled	= srv_cmp_per_index_enabled;
+
+	page_t* page = block->page.frame;
+	page_zip_des_t* page_zip = &block->page.zip;
+
+	ut_a(page_is_comp(page));
+	ut_a(fil_page_index_page_check(page));
+	ut_ad(page_simple_validate_new((page_t*) page));
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(dict_table_is_comp(index->table));
+	ut_ad(!dict_index_is_ibuf(index));
+
+	MEM_CHECK_DEFINED(page, srv_page_size);
+
+	/* Check the data that will be omitted. */
+	ut_a(!memcmp(page + (PAGE_NEW_INFIMUM - REC_N_NEW_EXTRA_BYTES),
+		     infimum_extra, sizeof infimum_extra));
+	ut_a(!memcmp(page + PAGE_NEW_INFIMUM,
+		     infimum_data, sizeof infimum_data));
+	ut_a(page[PAGE_NEW_SUPREMUM - REC_N_NEW_EXTRA_BYTES]
+	     /* info_bits == 0, n_owned <= max */
+	     <= PAGE_DIR_SLOT_MAX_N_OWNED);
+	ut_a(!memcmp(page + (PAGE_NEW_SUPREMUM - REC_N_NEW_EXTRA_BYTES + 1),
+		     supremum_extra_data, sizeof supremum_extra_data));
+
+	if (page_is_empty(page)) {
+		ut_a(rec_get_next_offs(page + PAGE_NEW_INFIMUM, TRUE)
+		     == PAGE_NEW_SUPREMUM);
+	}
+
+	const ulint n_fields = page_is_leaf(page)
+		? dict_index_get_n_fields(index)
+		: dict_index_get_n_unique_in_tree_nonleaf(index);
+	index_id_t ind_id = index->id;
+
+	/* The dense directory excludes the infimum and supremum records. */
+	n_dense = ulint(page_dir_get_n_heap(page)) - PAGE_HEAP_NO_USER_LOW;
+#ifdef PAGE_ZIP_COMPRESS_DBG
+	if (UNIV_UNLIKELY(page_zip_compress_dbg)) {
+		ib::info() << "compress "
+			<< static_cast<void*>(page_zip) << " "
+			<< static_cast<const void*>(page) << " "
+			<< page_is_leaf(page) << " "
+			<< n_fields << " " << n_dense;
+	}
+
+	if (UNIV_UNLIKELY(page_zip_compress_log)) {
+		/* Create a log file for every compression attempt. */
+		char	logfilename[9];
+		snprintf(logfilename, sizeof logfilename,
+			 "%08x", page_zip_compress_log++);
+		logfile = fopen(logfilename, "wb");
+
+		if (logfile) {
+			/* Write the uncompressed page to the log. */
+			if (fwrite(page, 1, srv_page_size, logfile)
+			    != srv_page_size) {
+				perror("fwrite");
+			}
+			/* Record the compressed size as zero.
+			This will be overwritten at successful exit. */
+			putc(0, logfile);
+			putc(0, logfile);
+			putc(0, logfile);
+			putc(0, logfile);
+		}
+	}
+#endif /* PAGE_ZIP_COMPRESS_DBG */
+	page_zip_stat[page_zip->ssize - 1].compressed++;
+	if (cmp_per_index_enabled) {
+		mysql_mutex_lock(&page_zip_stat_per_index_mutex);
+		page_zip_stat_per_index[ind_id].compressed++;
+		mysql_mutex_unlock(&page_zip_stat_per_index_mutex);
+	}
+
+	if (UNIV_UNLIKELY(n_dense * PAGE_ZIP_DIR_SLOT_SIZE
+			  >= page_zip_get_size(page_zip))) {
+
+		goto err_exit;
+	}
+
+	MONITOR_INC(MONITOR_PAGE_COMPRESS);
+
+	heap = mem_heap_create(page_zip_get_size(page_zip)
+			       + n_fields * (2 + sizeof(ulint))
+			       + REC_OFFS_HEADER_SIZE
+			       + n_dense * ((sizeof *recs)
+					    - PAGE_ZIP_DIR_SLOT_SIZE)
+			       + srv_page_size * 4
+			       + (512 << MAX_MEM_LEVEL));
+
+	recs = static_cast<const rec_t**>(
+		mem_heap_zalloc(heap, n_dense * sizeof *recs));
+
+	fields = static_cast<byte*>(mem_heap_alloc(heap, (n_fields + 1) * 2));
+
+	buf = static_cast<byte*>(
+		mem_heap_alloc(heap, page_zip_get_size(page_zip) - PAGE_DATA));
+
+	buf_end = buf + page_zip_get_size(page_zip) - PAGE_DATA;
+
+	/* Compress the data payload. */
+	page_zip_set_alloc(&c_stream, heap);
+
+	err = deflateInit2(&c_stream, static_cast<int>(level),
+			   Z_DEFLATED, static_cast<int>(srv_page_size_shift),
+			   MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY);
+	ut_a(err == Z_OK);
+
+	c_stream.next_out = buf;
+
+	/* Subtract the space reserved for uncompressed data. */
+	/* Page header and the end marker of the modification log */
+	c_stream.avail_out = static_cast<uInt>(buf_end - buf - 1);
+
+	/* Dense page directory and uncompressed columns, if any */
+	if (page_is_leaf(page)) {
+		if (dict_index_is_clust(index)) {
+			trx_id_col = index->db_trx_id();
+
+			slot_size = PAGE_ZIP_DIR_SLOT_SIZE
+				+ DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+
+		} else {
+			/* Signal the absence of trx_id
+			in page_zip_fields_encode() */
+			trx_id_col = 0;
+			slot_size = PAGE_ZIP_DIR_SLOT_SIZE;
+		}
+	} else {
+		slot_size = PAGE_ZIP_DIR_SLOT_SIZE + REC_NODE_PTR_SIZE;
+		trx_id_col = ULINT_UNDEFINED;
+	}
+
+	if (UNIV_UNLIKELY(c_stream.avail_out <= n_dense * slot_size
+			  + 6/* sizeof(zlib header and footer) */)) {
+		goto zlib_error;
+	}
+
+	c_stream.avail_out -= uInt(n_dense * slot_size);
+	c_stream.avail_in = uInt(page_zip_fields_encode(n_fields, index,
+							trx_id_col, fields));
+	c_stream.next_in = fields;
+
+	if (UNIV_LIKELY(!trx_id_col)) {
+		trx_id_col = ULINT_UNDEFINED;
+	}
+
+	MEM_CHECK_DEFINED(c_stream.next_in, c_stream.avail_in);
+	err = deflate(&c_stream, Z_FULL_FLUSH);
+	if (err != Z_OK) {
+		goto zlib_error;
+	}
+
+	ut_ad(!c_stream.avail_in);
+
+	page_zip_dir_encode(page, buf_end, recs);
+
+	c_stream.next_in = (byte*) page + PAGE_ZIP_START;
+
+	storage = buf_end - n_dense * PAGE_ZIP_DIR_SLOT_SIZE;
+
+	/* Compress the records in heap_no order. */
+	if (UNIV_UNLIKELY(!n_dense)) {
+	} else if (!page_is_leaf(page)) {
+		/* This is a node pointer page. */
+		err = page_zip_compress_node_ptrs(LOGFILE
+						  &c_stream, recs, n_dense,
+						  index, storage, heap);
+		if (UNIV_UNLIKELY(err != Z_OK)) {
+			goto zlib_error;
+		}
+	} else if (UNIV_LIKELY(trx_id_col == ULINT_UNDEFINED)) {
+		/* This is a leaf page in a secondary index. */
+		err = page_zip_compress_sec(LOGFILE
+					    &c_stream, recs, n_dense);
+		if (UNIV_UNLIKELY(err != Z_OK)) {
+			goto zlib_error;
+		}
+	} else {
+		/* This is a leaf page in a clustered index. */
+		err = page_zip_compress_clust(LOGFILE
+					      &c_stream, recs, n_dense,
+					      index, &n_blobs, trx_id_col,
+					      buf_end - PAGE_ZIP_DIR_SLOT_SIZE
+					      * page_get_n_recs(page),
+					      storage, heap);
+		if (UNIV_UNLIKELY(err != Z_OK)) {
+			goto zlib_error;
+		}
+	}
+
+	/* Finish the compression. */
+	ut_ad(!c_stream.avail_in);
+	/* Compress any trailing garbage, in case the last record was
+	allocated from an originally longer space on the free list,
+	or the data of the last record from page_zip_compress_sec(). */
+	c_stream.avail_in = static_cast<uInt>(
+		page_header_get_field(page, PAGE_HEAP_TOP)
+		- (c_stream.next_in - page));
+	ut_a(c_stream.avail_in <= srv_page_size - PAGE_ZIP_START - PAGE_DIR);
+
+	MEM_CHECK_DEFINED(c_stream.next_in, c_stream.avail_in);
+	err = deflate(&c_stream, Z_FINISH);
+
+	if (UNIV_UNLIKELY(err != Z_STREAM_END)) {
+zlib_error:
+		deflateEnd(&c_stream);
+		mem_heap_free(heap);
+err_exit:
+#ifdef PAGE_ZIP_COMPRESS_DBG
+		if (logfile) {
+			fclose(logfile);
+		}
+#endif /* PAGE_ZIP_COMPRESS_DBG */
+		if (page_is_leaf(page)) {
+			dict_index_zip_failure(index);
+		}
+
+		const uint64_t time_diff = (my_interval_timer() - ns) / 1000;
+		page_zip_stat[page_zip->ssize - 1].compressed_usec
+			+= time_diff;
+		if (cmp_per_index_enabled) {
+			mysql_mutex_lock(&page_zip_stat_per_index_mutex);
+			page_zip_stat_per_index[ind_id].compressed_usec
+				+= time_diff;
+			mysql_mutex_unlock(&page_zip_stat_per_index_mutex);
+		}
+		return false;
+	}
+
+	err = deflateEnd(&c_stream);
+	ut_a(err == Z_OK);
+
+	ut_ad(buf + c_stream.total_out == c_stream.next_out);
+	ut_ad((ulint) (storage - c_stream.next_out) >= c_stream.avail_out);
+
+#if defined HAVE_valgrind && !__has_feature(memory_sanitizer)
+	/* Valgrind believes that zlib does not initialize some bits
+	in the last 7 or 8 bytes of the stream.  Make Valgrind happy. */
+	MEM_MAKE_DEFINED(buf, c_stream.total_out);
+#endif /* HAVE_valgrind && !memory_sanitizer */
+
+	/* Zero out the area reserved for the modification log.
+	Space for the end marker of the modification log is not
+	included in avail_out. */
+	memset(c_stream.next_out, 0, c_stream.avail_out + 1/* end marker */);
+
+#ifdef UNIV_DEBUG
+	page_zip->m_start =
+#endif /* UNIV_DEBUG */
+		page_zip->m_end = uint16_t(PAGE_DATA + c_stream.total_out);
+	page_zip->m_nonempty = FALSE;
+	page_zip->n_blobs = unsigned(n_blobs) & ((1U << 12) - 1);
+	/* Copy those header fields that will not be written
+	in buf_flush_init_for_writing() */
+	memcpy_aligned<8>(page_zip->data + FIL_PAGE_PREV, page + FIL_PAGE_PREV,
+			  FIL_PAGE_LSN - FIL_PAGE_PREV);
+	memcpy_aligned<2>(page_zip->data + FIL_PAGE_TYPE, page + FIL_PAGE_TYPE,
+			  2);
+	memcpy_aligned<2>(page_zip->data + FIL_PAGE_DATA, page + FIL_PAGE_DATA,
+			  PAGE_DATA - FIL_PAGE_DATA);
+	/* Copy the rest of the compressed page */
+	memcpy_aligned<2>(page_zip->data + PAGE_DATA, buf,
+			  page_zip_get_size(page_zip) - PAGE_DATA);
+	mem_heap_free(heap);
+#ifdef UNIV_ZIP_DEBUG
+	ut_a(page_zip_validate(page_zip, page, index));
+#endif /* UNIV_ZIP_DEBUG */
+
+	page_zip_compress_write_log(block, index, mtr);
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+
+#ifdef PAGE_ZIP_COMPRESS_DBG
+	if (logfile) {
+		/* Record the compressed size of the block. */
+		byte sz[4];
+		mach_write_to_4(sz, c_stream.total_out);
+		fseek(logfile, srv_page_size, SEEK_SET);
+		if (fwrite(sz, 1, sizeof sz, logfile) != sizeof sz) {
+			perror("fwrite");
+		}
+		fclose(logfile);
+	}
+#endif /* PAGE_ZIP_COMPRESS_DBG */
+	const uint64_t time_diff = (my_interval_timer() - ns) / 1000;
+	page_zip_stat[page_zip->ssize - 1].compressed_ok++;
+	page_zip_stat[page_zip->ssize - 1].compressed_usec += time_diff;
+	if (cmp_per_index_enabled) {
+		mysql_mutex_lock(&page_zip_stat_per_index_mutex);
+		page_zip_stat_per_index[ind_id].compressed_ok++;
+		page_zip_stat_per_index[ind_id].compressed_usec += time_diff;
+		mysql_mutex_unlock(&page_zip_stat_per_index_mutex);
+	}
+
+	if (page_is_leaf(page)) {
+		dict_index_zip_success(index);
+	}
+
+	return true;
+}
+
+/**********************************************************************//**
+Deallocate the index information initialized by page_zip_fields_decode(). */
+static
+void
+page_zip_fields_free(
+/*=================*/
+	dict_index_t*	index)	/*!< in: dummy index to be freed */
+{
+	if (index) {
+		dict_table_t*	table = index->table;
+		index->zip_pad.mutex.~mutex();
+		mem_heap_free(index->heap);
+
+		dict_mem_table_free(table);
+	}
+}
+
+/**********************************************************************//**
+Read the index information for the compressed page.
+@return own: dummy index describing the page, or NULL on error */
+static
+dict_index_t*
+page_zip_fields_decode(
+/*===================*/
+	const byte*	buf,	/*!< in: index information */
+	const byte*	end,	/*!< in: end of buf */
+	ulint*		trx_id_col,/*!< in: NULL for non-leaf pages;
+				for leaf pages, pointer to where to store
+				the position of the trx_id column */
+	bool		is_spatial)/*< in: is spatial index or not */
+{
+	const byte*	b;
+	ulint		n;
+	ulint		i;
+	ulint		val;
+	dict_table_t*	table;
+	dict_index_t*	index;
+
+	/* Determine the number of fields. */
+	for (b = buf, n = 0; b < end; n++) {
+		if (*b++ & 0x80) {
+			b++; /* skip the second byte */
+		}
+	}
+
+	n--; /* n_nullable or trx_id */
+
+	if (UNIV_UNLIKELY(n > REC_MAX_N_FIELDS)) {
+
+		page_zip_fail(("page_zip_fields_decode: n = %lu\n",
+			       (ulong) n));
+		return(NULL);
+	}
+
+	if (UNIV_UNLIKELY(b > end)) {
+
+		page_zip_fail(("page_zip_fields_decode: %p > %p\n",
+			       (const void*) b, (const void*) end));
+		return(NULL);
+	}
+
+	table = dict_table_t::create({C_STRING_WITH_LEN("ZIP_DUMMY")},
+				     nullptr, n, 0, DICT_TF_COMPACT, 0);
+	index = dict_mem_index_create(table, "ZIP_DUMMY", 0, n);
+	index->n_uniq = static_cast<unsigned>(n) & dict_index_t::MAX_N_FIELDS;
+	/* avoid ut_ad(index->cached) in dict_index_get_n_unique_in_tree */
+	index->cached = TRUE;
+
+	/* Initialize the fields. */
+	for (b = buf, i = 0; i < n; i++) {
+		ulint	mtype;
+		ulint	len;
+
+		val = *b++;
+
+		if (UNIV_UNLIKELY(val & 0x80)) {
+			/* fixed length > 62 bytes */
+			val = (val & 0x7f) << 8 | *b++;
+			len = val >> 1;
+			mtype = DATA_FIXBINARY;
+		} else if (UNIV_UNLIKELY(val >= 126)) {
+			/* variable length with max > 255 bytes */
+			len = 0x7fff;
+			mtype = DATA_BINARY;
+		} else if (val <= 1) {
+			/* variable length with max <= 255 bytes */
+			len = 0;
+			mtype = DATA_BINARY;
+		} else {
+			/* fixed length < 62 bytes */
+			len = val >> 1;
+			mtype = DATA_FIXBINARY;
+		}
+
+		dict_mem_table_add_col(table, NULL, NULL, mtype,
+				       val & 1 ? DATA_NOT_NULL : 0, len);
+		dict_index_add_col(index, table,
+				   dict_table_get_nth_col(table, i), 0);
+	}
+
+	val = *b++;
+	if (UNIV_UNLIKELY(val & 0x80)) {
+		val = (val & 0x7f) << 8 | *b++;
+	}
+
+	/* Decode the position of the trx_id column. */
+	if (trx_id_col) {
+		if (!val) {
+			val = ULINT_UNDEFINED;
+		} else if (UNIV_UNLIKELY(val >= n)) {
+fail:
+			page_zip_fields_free(index);
+			return NULL;
+		} else {
+			index->type = DICT_CLUSTERED;
+		}
+
+		*trx_id_col = val;
+	} else {
+		/* Decode the number of nullable fields. */
+		if (UNIV_UNLIKELY(index->n_nullable > val)) {
+			goto fail;
+		} else {
+			index->n_nullable = static_cast<unsigned>(val)
+				& dict_index_t::MAX_N_FIELDS;
+		}
+	}
+
+	/* ROW_FORMAT=COMPRESSED does not support instant ADD COLUMN */
+	index->n_core_fields = index->n_fields;
+	index->n_core_null_bytes = static_cast<uint8_t>(
+		UT_BITS_IN_BYTES(unsigned(index->n_nullable)));
+
+	ut_ad(b == end);
+
+	if (is_spatial) {
+		index->type |= DICT_SPATIAL;
+	}
+
+	return(index);
+}
+
+/**********************************************************************//**
+Populate the sparse page directory from the dense directory.
+@return TRUE on success, FALSE on failure */
+static MY_ATTRIBUTE((nonnull, warn_unused_result))
+ibool
+page_zip_dir_decode(
+/*================*/
+	const page_zip_des_t*	page_zip,/*!< in: dense page directory on
+					compressed page */
+	page_t*			page,	/*!< in: compact page with valid header;
+					out: trailer and sparse page directory
+					filled in */
+	rec_t**			recs,	/*!< out: dense page directory sorted by
+					ascending address (and heap_no) */
+	ulint			n_dense)/*!< in: number of user records, and
+					size of recs[] */
+{
+	ulint	i;
+	ulint	n_recs;
+	byte*	slot;
+
+	n_recs = page_get_n_recs(page);
+
+	if (UNIV_UNLIKELY(n_recs > n_dense)) {
+		page_zip_fail(("page_zip_dir_decode 1: %lu > %lu\n",
+			       (ulong) n_recs, (ulong) n_dense));
+		return(FALSE);
+	}
+
+	/* Traverse the list of stored records in the sorting order,
+	starting from the first user record. */
+
+	slot = page + (srv_page_size - PAGE_DIR - PAGE_DIR_SLOT_SIZE);
+	UNIV_PREFETCH_RW(slot);
+
+	/* Zero out the page trailer. */
+	memset(slot + PAGE_DIR_SLOT_SIZE, 0, PAGE_DIR);
+
+	mach_write_to_2(slot, PAGE_NEW_INFIMUM);
+	slot -= PAGE_DIR_SLOT_SIZE;
+	UNIV_PREFETCH_RW(slot);
+
+	/* Initialize the sparse directory and copy the dense directory. */
+	for (i = 0; i < n_recs; i++) {
+		ulint	offs = page_zip_dir_get(page_zip, i);
+
+		if (offs & PAGE_ZIP_DIR_SLOT_OWNED) {
+			mach_write_to_2(slot, offs & PAGE_ZIP_DIR_SLOT_MASK);
+			slot -= PAGE_DIR_SLOT_SIZE;
+			UNIV_PREFETCH_RW(slot);
+		}
+
+		if (UNIV_UNLIKELY((offs & PAGE_ZIP_DIR_SLOT_MASK)
+				  < PAGE_ZIP_START + REC_N_NEW_EXTRA_BYTES)) {
+			page_zip_fail(("page_zip_dir_decode 2: %u %u %lx\n",
+				       (unsigned) i, (unsigned) n_recs,
+				       (ulong) offs));
+			return(FALSE);
+		}
+
+		recs[i] = page + (offs & PAGE_ZIP_DIR_SLOT_MASK);
+	}
+
+	mach_write_to_2(slot, PAGE_NEW_SUPREMUM);
+	{
+		const page_dir_slot_t*	last_slot = page_dir_get_nth_slot(
+			page, page_dir_get_n_slots(page) - 1U);
+
+		if (UNIV_UNLIKELY(slot != last_slot)) {
+			page_zip_fail(("page_zip_dir_decode 3: %p != %p\n",
+				       (const void*) slot,
+				       (const void*) last_slot));
+			return(FALSE);
+		}
+	}
+
+	/* Copy the rest of the dense directory. */
+	for (; i < n_dense; i++) {
+		ulint	offs = page_zip_dir_get(page_zip, i);
+
+		if (UNIV_UNLIKELY(offs & ~PAGE_ZIP_DIR_SLOT_MASK)) {
+			page_zip_fail(("page_zip_dir_decode 4: %u %u %lx\n",
+				       (unsigned) i, (unsigned) n_dense,
+				       (ulong) offs));
+			return(FALSE);
+		}
+
+		recs[i] = page + offs;
+	}
+
+	std::sort(recs, recs + n_dense);
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Initialize the REC_N_NEW_EXTRA_BYTES of each record.
+@return TRUE on success, FALSE on failure */
+static
+ibool
+page_zip_set_extra_bytes(
+/*=====================*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	page_t*			page,	/*!< in/out: uncompressed page */
+	ulint			info_bits)/*!< in: REC_INFO_MIN_REC_FLAG or 0 */
+{
+	ulint	n;
+	ulint	i;
+	ulint	n_owned = 1;
+	ulint	offs;
+	rec_t*	rec;
+
+	n = page_get_n_recs(page);
+	rec = page + PAGE_NEW_INFIMUM;
+
+	for (i = 0; i < n; i++) {
+		offs = page_zip_dir_get(page_zip, i);
+
+		if (offs & PAGE_ZIP_DIR_SLOT_DEL) {
+			info_bits |= REC_INFO_DELETED_FLAG;
+		}
+		if (UNIV_UNLIKELY(offs & PAGE_ZIP_DIR_SLOT_OWNED)) {
+			info_bits |= n_owned;
+			n_owned = 1;
+		} else {
+			n_owned++;
+		}
+		offs &= PAGE_ZIP_DIR_SLOT_MASK;
+		if (UNIV_UNLIKELY(offs < PAGE_ZIP_START
+				  + REC_N_NEW_EXTRA_BYTES)) {
+			page_zip_fail(("page_zip_set_extra_bytes 1:"
+				       " %u %u %lx\n",
+				       (unsigned) i, (unsigned) n,
+				       (ulong) offs));
+			return(FALSE);
+		}
+
+		rec_set_next_offs_new(rec, offs);
+		rec = page + offs;
+		rec[-REC_N_NEW_EXTRA_BYTES] = (byte) info_bits;
+		info_bits = 0;
+	}
+
+	/* Set the next pointer of the last user record. */
+	rec_set_next_offs_new(rec, PAGE_NEW_SUPREMUM);
+
+	/* Set n_owned of the supremum record. */
+	page[PAGE_NEW_SUPREMUM - REC_N_NEW_EXTRA_BYTES] = (byte) n_owned;
+
+	/* The dense directory excludes the infimum and supremum records. */
+	n = ulint(page_dir_get_n_heap(page)) - PAGE_HEAP_NO_USER_LOW;
+
+	if (i >= n) {
+		if (UNIV_LIKELY(i == n)) {
+			return(TRUE);
+		}
+
+		page_zip_fail(("page_zip_set_extra_bytes 2: %u != %u\n",
+			       (unsigned) i, (unsigned) n));
+		return(FALSE);
+	}
+
+	offs = page_zip_dir_get(page_zip, i);
+
+	/* Set the extra bytes of deleted records on the free list. */
+	for (;;) {
+		if (UNIV_UNLIKELY(!offs)
+		    || UNIV_UNLIKELY(offs & ~PAGE_ZIP_DIR_SLOT_MASK)) {
+
+			page_zip_fail(("page_zip_set_extra_bytes 3: %lx\n",
+				       (ulong) offs));
+			return(FALSE);
+		}
+
+		rec = page + offs;
+		rec[-REC_N_NEW_EXTRA_BYTES] = 0; /* info_bits and n_owned */
+
+		if (++i == n) {
+			break;
+		}
+
+		offs = page_zip_dir_get(page_zip, i);
+		rec_set_next_offs_new(rec, offs);
+	}
+
+	/* Terminate the free list. */
+	rec[-REC_N_NEW_EXTRA_BYTES] = 0; /* info_bits and n_owned */
+	rec_set_next_offs_new(rec, 0);
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Apply the modification log to a record containing externally stored
+columns.  Do not copy the fields that are stored separately.
+@return pointer to modification log, or NULL on failure */
+static
+const byte*
+page_zip_apply_log_ext(
+/*===================*/
+	rec_t*		rec,		/*!< in/out: record */
+	const rec_offs*	offsets,	/*!< in: rec_get_offsets(rec) */
+	ulint		trx_id_col,	/*!< in: position of of DB_TRX_ID */
+	const byte*	data,		/*!< in: modification log */
+	const byte*	end)		/*!< in: end of modification log */
+{
+	ulint	i;
+	ulint	len;
+	byte*	next_out = rec;
+
+	/* Check if there are any externally stored columns.
+	For each externally stored column, skip the
+	BTR_EXTERN_FIELD_REF. */
+
+	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
+		byte*	dst;
+
+		if (UNIV_UNLIKELY(i == trx_id_col)) {
+			/* Skip trx_id and roll_ptr */
+			dst = rec_get_nth_field(rec, offsets,
+						i, &len);
+			if (UNIV_UNLIKELY(dst - next_out >= end - data)
+			    || UNIV_UNLIKELY
+			    (len < (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN))
+			    || rec_offs_nth_extern(offsets, i)) {
+				page_zip_fail(("page_zip_apply_log_ext:"
+					       " trx_id len %lu,"
+					       " %p - %p >= %p - %p\n",
+					       (ulong) len,
+					       (const void*) dst,
+					       (const void*) next_out,
+					       (const void*) end,
+					       (const void*) data));
+				return(NULL);
+			}
+
+			memcpy(next_out, data, ulint(dst - next_out));
+			data += ulint(dst - next_out);
+			next_out = dst + (DATA_TRX_ID_LEN
+					  + DATA_ROLL_PTR_LEN);
+		} else if (rec_offs_nth_extern(offsets, i)) {
+			dst = rec_get_nth_field(rec, offsets,
+						i, &len);
+			ut_ad(len
+			      >= BTR_EXTERN_FIELD_REF_SIZE);
+
+			len += ulint(dst - next_out)
+				- BTR_EXTERN_FIELD_REF_SIZE;
+
+			if (UNIV_UNLIKELY(data + len >= end)) {
+				page_zip_fail(("page_zip_apply_log_ext:"
+					       " ext %p+%lu >= %p\n",
+					       (const void*) data,
+					       (ulong) len,
+					       (const void*) end));
+				return(NULL);
+			}
+
+			memcpy(next_out, data, len);
+			data += len;
+			next_out += len
+				+ BTR_EXTERN_FIELD_REF_SIZE;
+		}
+	}
+
+	/* Copy the last bytes of the record. */
+	len = ulint(rec_get_end(rec, offsets) - next_out);
+	if (UNIV_UNLIKELY(data + len >= end)) {
+		page_zip_fail(("page_zip_apply_log_ext:"
+			       " last %p+%lu >= %p\n",
+			       (const void*) data,
+			       (ulong) len,
+			       (const void*) end));
+		return(NULL);
+	}
+	memcpy(next_out, data, len);
+	data += len;
+
+	return(data);
+}
+
+/**********************************************************************//**
+Apply the modification log to an uncompressed page.
+Do not copy the fields that are stored separately.
+@return pointer to end of modification log, or NULL on failure */
+static
+const byte*
+page_zip_apply_log(
+/*===============*/
+	const byte*	data,	/*!< in: modification log */
+	ulint		size,	/*!< in: maximum length of the log, in bytes */
+	rec_t**		recs,	/*!< in: dense page directory,
+				sorted by address (indexed by
+				heap_no - PAGE_HEAP_NO_USER_LOW) */
+	ulint		n_dense,/*!< in: size of recs[] */
+	ulint		n_core,	/*!< in: index->n_fields, or 0 for non-leaf */
+	ulint		trx_id_col,/*!< in: column number of trx_id in the index,
+				or ULINT_UNDEFINED if none */
+	ulint		heap_status,
+				/*!< in: heap_no and status bits for
+				the next record to uncompress */
+	dict_index_t*	index,	/*!< in: index of the page */
+	rec_offs*	offsets)/*!< in/out: work area for
+				rec_get_offsets_reverse() */
+{
+	const byte* const end = data + size;
+
+	for (;;) {
+		ulint	val;
+		rec_t*	rec;
+		ulint	len;
+		ulint	hs;
+
+		val = *data++;
+		if (UNIV_UNLIKELY(!val)) {
+			return(data - 1);
+		}
+		if (val & 0x80) {
+			val = (val & 0x7f) << 8 | *data++;
+			if (UNIV_UNLIKELY(!val)) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " invalid val %x%x\n",
+					       data[-2], data[-1]));
+				return(NULL);
+			}
+		}
+		if (UNIV_UNLIKELY(data >= end)) {
+			page_zip_fail(("page_zip_apply_log: %p >= %p\n",
+				       (const void*) data,
+				       (const void*) end));
+			return(NULL);
+		}
+		if (UNIV_UNLIKELY((val >> 1) > n_dense)) {
+			page_zip_fail(("page_zip_apply_log: %lu>>1 > %lu\n",
+				       (ulong) val, (ulong) n_dense));
+			return(NULL);
+		}
+
+		/* Determine the heap number and status bits of the record. */
+		rec = recs[(val >> 1) - 1];
+
+		hs = ((val >> 1) + 1) << REC_HEAP_NO_SHIFT;
+		hs |= heap_status & ((1 << REC_HEAP_NO_SHIFT) - 1);
+
+		/* This may either be an old record that is being
+		overwritten (updated in place, or allocated from
+		the free list), or a new record, with the next
+		available_heap_no. */
+		if (UNIV_UNLIKELY(hs > heap_status)) {
+			page_zip_fail(("page_zip_apply_log: %lu > %lu\n",
+				       (ulong) hs, (ulong) heap_status));
+			return(NULL);
+		} else if (hs == heap_status) {
+			/* A new record was allocated from the heap. */
+			if (UNIV_UNLIKELY(val & 1)) {
+				/* Only existing records may be cleared. */
+				page_zip_fail(("page_zip_apply_log:"
+					       " attempting to create"
+					       " deleted rec %lu\n",
+					       (ulong) hs));
+				return(NULL);
+			}
+			heap_status += 1 << REC_HEAP_NO_SHIFT;
+		}
+
+		mach_write_to_2(rec - REC_NEW_HEAP_NO, hs);
+
+		if (val & 1) {
+			/* Clear the data bytes of the record. */
+			mem_heap_t*	heap	= NULL;
+			rec_offs*	offs;
+			offs = rec_get_offsets(rec, index, offsets, n_core,
+					       ULINT_UNDEFINED, &heap);
+			memset(rec, 0, rec_offs_data_size(offs));
+
+			if (UNIV_LIKELY_NULL(heap)) {
+				mem_heap_free(heap);
+			}
+			continue;
+		}
+
+		compile_time_assert(REC_STATUS_NODE_PTR == TRUE);
+		rec_get_offsets_reverse(data, index,
+					hs & REC_STATUS_NODE_PTR,
+					offsets);
+		/* Silence a debug assertion in rec_offs_make_valid().
+		This will be overwritten in page_zip_set_extra_bytes(),
+		called by page_zip_decompress_low(). */
+		ut_d(rec[-REC_NEW_INFO_BITS] = 0);
+		rec_offs_make_valid(rec, index, n_core != 0, offsets);
+
+		/* Copy the extra bytes (backwards). */
+		{
+			byte*	start	= rec_get_start(rec, offsets);
+			byte*	b	= rec - REC_N_NEW_EXTRA_BYTES;
+			while (b != start) {
+				*--b = *data++;
+			}
+		}
+
+		/* Copy the data bytes. */
+		if (UNIV_UNLIKELY(rec_offs_any_extern(offsets))) {
+			/* Non-leaf nodes should not contain any
+			externally stored columns. */
+			if (UNIV_UNLIKELY(hs & REC_STATUS_NODE_PTR)) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " %lu&REC_STATUS_NODE_PTR\n",
+					       (ulong) hs));
+				return(NULL);
+			}
+
+			data = page_zip_apply_log_ext(
+				rec, offsets, trx_id_col, data, end);
+
+			if (UNIV_UNLIKELY(!data)) {
+				return(NULL);
+			}
+		} else if (UNIV_UNLIKELY(hs & REC_STATUS_NODE_PTR)) {
+			len = rec_offs_data_size(offsets)
+				- REC_NODE_PTR_SIZE;
+			/* Copy the data bytes, except node_ptr. */
+			if (UNIV_UNLIKELY(data + len >= end)) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " node_ptr %p+%lu >= %p\n",
+					       (const void*) data,
+					       (ulong) len,
+					       (const void*) end));
+				return(NULL);
+			}
+			memcpy(rec, data, len);
+			data += len;
+		} else if (UNIV_LIKELY(trx_id_col == ULINT_UNDEFINED)) {
+			len = rec_offs_data_size(offsets);
+
+			/* Copy all data bytes of
+			a record in a secondary index. */
+			if (UNIV_UNLIKELY(data + len >= end)) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " sec %p+%lu >= %p\n",
+					       (const void*) data,
+					       (ulong) len,
+					       (const void*) end));
+				return(NULL);
+			}
+
+			memcpy(rec, data, len);
+			data += len;
+		} else {
+			/* Skip DB_TRX_ID and DB_ROLL_PTR. */
+			ulint	l = rec_get_nth_field_offs(offsets,
+							   trx_id_col, &len);
+			byte*	b;
+
+			if (UNIV_UNLIKELY(data + l >= end)
+			    || UNIV_UNLIKELY(len < (DATA_TRX_ID_LEN
+						    + DATA_ROLL_PTR_LEN))) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " trx_id %p+%lu >= %p\n",
+					       (const void*) data,
+					       (ulong) l,
+					       (const void*) end));
+				return(NULL);
+			}
+
+			/* Copy any preceding data bytes. */
+			memcpy(rec, data, l);
+			data += l;
+
+			/* Copy any bytes following DB_TRX_ID, DB_ROLL_PTR. */
+			b = rec + l + (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+			len = ulint(rec_get_end(rec, offsets) - b);
+			if (UNIV_UNLIKELY(data + len >= end)) {
+				page_zip_fail(("page_zip_apply_log:"
+					       " clust %p+%lu >= %p\n",
+					       (const void*) data,
+					       (ulong) len,
+					       (const void*) end));
+				return(NULL);
+			}
+			memcpy(b, data, len);
+			data += len;
+		}
+	}
+}
+
+/**********************************************************************//**
+Set the heap_no in a record, and skip the fixed-size record header
+that is not included in the d_stream.
+@return TRUE on success, FALSE if d_stream does not end at rec */
+static
+ibool
+page_zip_decompress_heap_no(
+/*========================*/
+	z_stream*	d_stream,	/*!< in/out: compressed page stream */
+	rec_t*		rec,		/*!< in/out: record */
+	ulint&		heap_status)	/*!< in/out: heap_no and status bits */
+{
+	if (d_stream->next_out != rec - REC_N_NEW_EXTRA_BYTES) {
+		/* n_dense has grown since the page was last compressed. */
+		return(FALSE);
+	}
+
+	/* Skip the REC_N_NEW_EXTRA_BYTES. */
+	d_stream->next_out = rec;
+
+	/* Set heap_no and the status bits. */
+	mach_write_to_2(rec - REC_NEW_HEAP_NO, heap_status);
+	heap_status += 1 << REC_HEAP_NO_SHIFT;
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Decompress the records of a node pointer page.
+@return TRUE on success, FALSE on failure */
+static
+ibool
+page_zip_decompress_node_ptrs(
+/*==========================*/
+	page_zip_des_t*	page_zip,	/*!< in/out: compressed page */
+	z_stream*	d_stream,	/*!< in/out: compressed page stream */
+	rec_t**		recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense,	/*!< in: size of recs[] */
+	dict_index_t*	index,		/*!< in: the index of the page */
+	rec_offs*	offsets,	/*!< in/out: temporary offsets */
+	mem_heap_t*	heap)		/*!< in: temporary memory heap */
+{
+	ulint		heap_status = REC_STATUS_NODE_PTR
+		| PAGE_HEAP_NO_USER_LOW << REC_HEAP_NO_SHIFT;
+	ulint		slot;
+	const byte*	storage;
+
+	/* Subtract the space reserved for uncompressed data. */
+	d_stream->avail_in -= static_cast<uInt>(
+		n_dense * (PAGE_ZIP_DIR_SLOT_SIZE + REC_NODE_PTR_SIZE));
+
+	/* Decompress the records in heap_no order. */
+	for (slot = 0; slot < n_dense; slot++) {
+		rec_t*	rec = recs[slot];
+
+		d_stream->avail_out = static_cast<uInt>(
+			rec - REC_N_NEW_EXTRA_BYTES - d_stream->next_out);
+
+		ut_ad(d_stream->avail_out < srv_page_size
+		      - PAGE_ZIP_START - PAGE_DIR);
+		switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+		case Z_STREAM_END:
+			page_zip_decompress_heap_no(
+				d_stream, rec, heap_status);
+			goto zlib_done;
+		case Z_OK:
+		case Z_BUF_ERROR:
+			if (!d_stream->avail_out) {
+				break;
+			}
+			/* fall through */
+		default:
+			page_zip_fail(("page_zip_decompress_node_ptrs:"
+				       " 1 inflate(Z_SYNC_FLUSH)=%s\n",
+				       d_stream->msg));
+			goto zlib_error;
+		}
+
+		if (!page_zip_decompress_heap_no(
+			    d_stream, rec, heap_status)) {
+			ut_ad(0);
+		}
+
+		/* Read the offsets. The status bits are needed here. */
+		offsets = rec_get_offsets(rec, index, offsets, 0,
+					  ULINT_UNDEFINED, &heap);
+
+		/* Non-leaf nodes should not have any externally
+		stored columns. */
+		ut_ad(!rec_offs_any_extern(offsets));
+
+		/* Decompress the data bytes, except node_ptr. */
+		d_stream->avail_out =static_cast<uInt>(
+			rec_offs_data_size(offsets) - REC_NODE_PTR_SIZE);
+
+		switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+		case Z_STREAM_END:
+			goto zlib_done;
+		case Z_OK:
+		case Z_BUF_ERROR:
+			if (!d_stream->avail_out) {
+				break;
+			}
+			/* fall through */
+		default:
+			page_zip_fail(("page_zip_decompress_node_ptrs:"
+				       " 2 inflate(Z_SYNC_FLUSH)=%s\n",
+				       d_stream->msg));
+			goto zlib_error;
+		}
+
+		/* Clear the node pointer in case the record
+		will be deleted and the space will be reallocated
+		to a smaller record. */
+		memset(d_stream->next_out, 0, REC_NODE_PTR_SIZE);
+		d_stream->next_out += REC_NODE_PTR_SIZE;
+
+		ut_ad(d_stream->next_out == rec_get_end(rec, offsets));
+	}
+
+	/* Decompress any trailing garbage, in case the last record was
+	allocated from an originally longer space on the free list. */
+	d_stream->avail_out = static_cast<uInt>(
+		page_header_get_field(page_zip->data, PAGE_HEAP_TOP)
+		- page_offset(d_stream->next_out));
+	if (UNIV_UNLIKELY(d_stream->avail_out > srv_page_size
+			  - PAGE_ZIP_START - PAGE_DIR)) {
+
+		page_zip_fail(("page_zip_decompress_node_ptrs:"
+			       " avail_out = %u\n",
+			       d_stream->avail_out));
+		goto zlib_error;
+	}
+
+	if (UNIV_UNLIKELY(inflate(d_stream, Z_FINISH) != Z_STREAM_END)) {
+		page_zip_fail(("page_zip_decompress_node_ptrs:"
+			       " inflate(Z_FINISH)=%s\n",
+			       d_stream->msg));
+zlib_error:
+		inflateEnd(d_stream);
+		return(FALSE);
+	}
+
+	/* Note that d_stream->avail_out > 0 may hold here
+	if the modification log is nonempty. */
+
+zlib_done:
+	if (UNIV_UNLIKELY(inflateEnd(d_stream) != Z_OK)) {
+		ut_error;
+	}
+
+	{
+		page_t*	page = page_align(d_stream->next_out);
+
+		/* Clear the unused heap space on the uncompressed page. */
+		memset(d_stream->next_out, 0,
+		       ulint(page_dir_get_nth_slot(page,
+						   page_dir_get_n_slots(page)
+						   - 1U)
+			     - d_stream->next_out));
+	}
+
+#ifdef UNIV_DEBUG
+	page_zip->m_start = uint16_t(PAGE_DATA + d_stream->total_in);
+#endif /* UNIV_DEBUG */
+
+	/* Apply the modification log. */
+	{
+		const byte*	mod_log_ptr;
+		mod_log_ptr = page_zip_apply_log(d_stream->next_in,
+						 d_stream->avail_in + 1,
+						 recs, n_dense, 0,
+						 ULINT_UNDEFINED, heap_status,
+						 index, offsets);
+
+		if (UNIV_UNLIKELY(!mod_log_ptr)) {
+			return(FALSE);
+		}
+		page_zip->m_end = uint16_t(mod_log_ptr - page_zip->data);
+		page_zip->m_nonempty = mod_log_ptr != d_stream->next_in;
+	}
+
+	if (UNIV_UNLIKELY
+	    (page_zip_get_trailer_len(page_zip,
+				      dict_index_is_clust(index))
+	     + page_zip->m_end >= page_zip_get_size(page_zip))) {
+		page_zip_fail(("page_zip_decompress_node_ptrs:"
+			       " %lu + %lu >= %lu, %lu\n",
+			       (ulong) page_zip_get_trailer_len(
+				       page_zip, dict_index_is_clust(index)),
+			       (ulong) page_zip->m_end,
+			       (ulong) page_zip_get_size(page_zip),
+			       (ulong) dict_index_is_clust(index)));
+		return(FALSE);
+	}
+
+	/* Restore the uncompressed columns in heap_no order. */
+	storage = page_zip_dir_start_low(page_zip, n_dense);
+
+	for (slot = 0; slot < n_dense; slot++) {
+		rec_t*		rec	= recs[slot];
+
+		offsets = rec_get_offsets(rec, index, offsets, 0,
+					  ULINT_UNDEFINED, &heap);
+		/* Non-leaf nodes should not have any externally
+		stored columns. */
+		ut_ad(!rec_offs_any_extern(offsets));
+		storage -= REC_NODE_PTR_SIZE;
+
+		memcpy(rec_get_end(rec, offsets) - REC_NODE_PTR_SIZE,
+		       storage, REC_NODE_PTR_SIZE);
+	}
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Decompress the records of a leaf node of a secondary index.
+@return TRUE on success, FALSE on failure */
+static
+ibool
+page_zip_decompress_sec(
+/*====================*/
+	page_zip_des_t*	page_zip,	/*!< in/out: compressed page */
+	z_stream*	d_stream,	/*!< in/out: compressed page stream */
+	rec_t**		recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense,	/*!< in: size of recs[] */
+	dict_index_t*	index,		/*!< in: the index of the page */
+	rec_offs*	offsets)	/*!< in/out: temporary offsets */
+{
+	ulint	heap_status	= REC_STATUS_ORDINARY
+		| PAGE_HEAP_NO_USER_LOW << REC_HEAP_NO_SHIFT;
+	ulint	slot;
+
+	ut_a(!dict_index_is_clust(index));
+
+	/* Subtract the space reserved for uncompressed data. */
+	d_stream->avail_in -= static_cast<uint>(
+		n_dense * PAGE_ZIP_DIR_SLOT_SIZE);
+
+	for (slot = 0; slot < n_dense; slot++) {
+		rec_t*	rec = recs[slot];
+
+		/* Decompress everything up to this record. */
+		d_stream->avail_out = static_cast<uint>(
+			rec - REC_N_NEW_EXTRA_BYTES - d_stream->next_out);
+
+		if (UNIV_LIKELY(d_stream->avail_out)) {
+			switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+			case Z_STREAM_END:
+				page_zip_decompress_heap_no(
+					d_stream, rec, heap_status);
+				goto zlib_done;
+			case Z_OK:
+			case Z_BUF_ERROR:
+				if (!d_stream->avail_out) {
+					break;
+				}
+				/* fall through */
+			default:
+				page_zip_fail(("page_zip_decompress_sec:"
+					       " inflate(Z_SYNC_FLUSH)=%s\n",
+					       d_stream->msg));
+				goto zlib_error;
+			}
+		}
+
+		if (!page_zip_decompress_heap_no(
+			    d_stream, rec, heap_status)) {
+			ut_ad(0);
+		}
+	}
+
+	/* Decompress the data of the last record and any trailing garbage,
+	in case the last record was allocated from an originally longer space
+	on the free list. */
+	d_stream->avail_out = static_cast<uInt>(
+		page_header_get_field(page_zip->data, PAGE_HEAP_TOP)
+		- page_offset(d_stream->next_out));
+	if (UNIV_UNLIKELY(d_stream->avail_out > srv_page_size
+			  - PAGE_ZIP_START - PAGE_DIR)) {
+
+		page_zip_fail(("page_zip_decompress_sec:"
+			       " avail_out = %u\n",
+			       d_stream->avail_out));
+		goto zlib_error;
+	}
+
+	if (UNIV_UNLIKELY(inflate(d_stream, Z_FINISH) != Z_STREAM_END)) {
+		page_zip_fail(("page_zip_decompress_sec:"
+			       " inflate(Z_FINISH)=%s\n",
+			       d_stream->msg));
+zlib_error:
+		inflateEnd(d_stream);
+		return(FALSE);
+	}
+
+	/* Note that d_stream->avail_out > 0 may hold here
+	if the modification log is nonempty. */
+
+zlib_done:
+	if (UNIV_UNLIKELY(inflateEnd(d_stream) != Z_OK)) {
+		ut_error;
+	}
+
+	{
+		page_t*	page = page_align(d_stream->next_out);
+
+		/* Clear the unused heap space on the uncompressed page. */
+		memset(d_stream->next_out, 0,
+		       ulint(page_dir_get_nth_slot(page,
+						   page_dir_get_n_slots(page)
+						   - 1U)
+			     - d_stream->next_out));
+	}
+
+	ut_d(page_zip->m_start = uint16_t(PAGE_DATA + d_stream->total_in));
+
+	/* Apply the modification log. */
+	{
+		const byte*	mod_log_ptr;
+		mod_log_ptr = page_zip_apply_log(d_stream->next_in,
+						 d_stream->avail_in + 1,
+						 recs, n_dense,
+						 index->n_fields,
+						 ULINT_UNDEFINED, heap_status,
+						 index, offsets);
+
+		if (UNIV_UNLIKELY(!mod_log_ptr)) {
+			return(FALSE);
+		}
+		page_zip->m_end = uint16_t(mod_log_ptr - page_zip->data);
+		page_zip->m_nonempty = mod_log_ptr != d_stream->next_in;
+	}
+
+	if (UNIV_UNLIKELY(page_zip_get_trailer_len(page_zip, FALSE)
+			  + page_zip->m_end >= page_zip_get_size(page_zip))) {
+
+		page_zip_fail(("page_zip_decompress_sec: %lu + %lu >= %lu\n",
+			       (ulong) page_zip_get_trailer_len(
+				       page_zip, FALSE),
+			       (ulong) page_zip->m_end,
+			       (ulong) page_zip_get_size(page_zip)));
+		return(FALSE);
+	}
+
+	/* There are no uncompressed columns on leaf pages of
+	secondary indexes. */
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Decompress a record of a leaf node of a clustered index that contains
+externally stored columns.
+@return TRUE on success */
+static
+ibool
+page_zip_decompress_clust_ext(
+/*==========================*/
+	z_stream*	d_stream,	/*!< in/out: compressed page stream */
+	rec_t*		rec,		/*!< in/out: record */
+	const rec_offs*	offsets,	/*!< in: rec_get_offsets(rec) */
+	ulint		trx_id_col)	/*!< in: position of of DB_TRX_ID */
+{
+	ulint	i;
+
+	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
+		ulint	len;
+		byte*	dst;
+
+		if (UNIV_UNLIKELY(i == trx_id_col)) {
+			/* Skip trx_id and roll_ptr */
+			dst = rec_get_nth_field(rec, offsets, i, &len);
+			if (UNIV_UNLIKELY(len < DATA_TRX_ID_LEN
+					  + DATA_ROLL_PTR_LEN)) {
+
+				page_zip_fail(("page_zip_decompress_clust_ext:"
+					       " len[%lu] = %lu\n",
+					       (ulong) i, (ulong) len));
+				return(FALSE);
+			}
+
+			if (rec_offs_nth_extern(offsets, i)) {
+
+				page_zip_fail(("page_zip_decompress_clust_ext:"
+					       " DB_TRX_ID at %lu is ext\n",
+					       (ulong) i));
+				return(FALSE);
+			}
+
+			d_stream->avail_out = static_cast<uInt>(
+				dst - d_stream->next_out);
+
+			switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+			case Z_STREAM_END:
+			case Z_OK:
+			case Z_BUF_ERROR:
+				if (!d_stream->avail_out) {
+					break;
+				}
+				/* fall through */
+			default:
+				page_zip_fail(("page_zip_decompress_clust_ext:"
+					       " 1 inflate(Z_SYNC_FLUSH)=%s\n",
+					       d_stream->msg));
+				return(FALSE);
+			}
+
+			ut_ad(d_stream->next_out == dst);
+
+			/* Clear DB_TRX_ID and DB_ROLL_PTR in order to
+			avoid uninitialized bytes in case the record
+			is affected by page_zip_apply_log(). */
+			memset(dst, 0, DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+			d_stream->next_out += DATA_TRX_ID_LEN
+				+ DATA_ROLL_PTR_LEN;
+		} else if (rec_offs_nth_extern(offsets, i)) {
+			dst = rec_get_nth_field(rec, offsets, i, &len);
+			ut_ad(len >= BTR_EXTERN_FIELD_REF_SIZE);
+			dst += len - BTR_EXTERN_FIELD_REF_SIZE;
+
+			d_stream->avail_out = static_cast<uInt>(
+				dst - d_stream->next_out);
+			switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+			case Z_STREAM_END:
+			case Z_OK:
+			case Z_BUF_ERROR:
+				if (!d_stream->avail_out) {
+					break;
+				}
+				/* fall through */
+			default:
+				page_zip_fail(("page_zip_decompress_clust_ext:"
+					       " 2 inflate(Z_SYNC_FLUSH)=%s\n",
+					       d_stream->msg));
+				return(FALSE);
+			}
+
+			ut_ad(d_stream->next_out == dst);
+
+			/* Clear the BLOB pointer in case
+			the record will be deleted and the
+			space will not be reused.  Note that
+			the final initialization of the BLOB
+			pointers (copying from "externs"
+			or clearing) will have to take place
+			only after the page modification log
+			has been applied.  Otherwise, we
+			could end up with an uninitialized
+			BLOB pointer when a record is deleted,
+			reallocated and deleted. */
+			memset(d_stream->next_out, 0,
+			       BTR_EXTERN_FIELD_REF_SIZE);
+			d_stream->next_out
+				+= BTR_EXTERN_FIELD_REF_SIZE;
+		}
+	}
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Compress the records of a leaf node of a clustered index.
+@return TRUE on success, FALSE on failure */
+static
+ibool
+page_zip_decompress_clust(
+/*======================*/
+	page_zip_des_t*	page_zip,	/*!< in/out: compressed page */
+	z_stream*	d_stream,	/*!< in/out: compressed page stream */
+	rec_t**		recs,		/*!< in: dense page directory
+					sorted by address */
+	ulint		n_dense,	/*!< in: size of recs[] */
+	dict_index_t*	index,		/*!< in: the index of the page */
+	ulint		trx_id_col,	/*!< index of the trx_id column */
+	rec_offs*	offsets,	/*!< in/out: temporary offsets */
+	mem_heap_t*	heap)		/*!< in: temporary memory heap */
+{
+	int		err;
+	ulint		slot;
+	ulint		heap_status	= REC_STATUS_ORDINARY
+		| PAGE_HEAP_NO_USER_LOW << REC_HEAP_NO_SHIFT;
+	const byte*	storage;
+	const byte*	externs;
+
+	ut_a(dict_index_is_clust(index));
+
+	/* Subtract the space reserved for uncompressed data. */
+	d_stream->avail_in -= static_cast<uInt>(n_dense)
+			    * (PAGE_ZIP_CLUST_LEAF_SLOT_SIZE);
+
+	/* Decompress the records in heap_no order. */
+	for (slot = 0; slot < n_dense; slot++) {
+		rec_t*	rec	= recs[slot];
+
+		d_stream->avail_out =static_cast<uInt>(
+			rec - REC_N_NEW_EXTRA_BYTES - d_stream->next_out);
+
+		ut_ad(d_stream->avail_out < srv_page_size
+		      - PAGE_ZIP_START - PAGE_DIR);
+		err = inflate(d_stream, Z_SYNC_FLUSH);
+		switch (err) {
+		case Z_STREAM_END:
+			page_zip_decompress_heap_no(
+				d_stream, rec, heap_status);
+			goto zlib_done;
+		case Z_OK:
+		case Z_BUF_ERROR:
+			if (UNIV_LIKELY(!d_stream->avail_out)) {
+				break;
+			}
+			/* fall through */
+		default:
+			page_zip_fail(("page_zip_decompress_clust:"
+				       " 1 inflate(Z_SYNC_FLUSH)=%s\n",
+				       d_stream->msg));
+			goto zlib_error;
+		}
+
+		if (!page_zip_decompress_heap_no(
+			    d_stream, rec, heap_status)) {
+			ut_ad(0);
+		}
+
+		/* Read the offsets. The status bits are needed here. */
+		offsets = rec_get_offsets(rec, index, offsets, index->n_fields,
+					  ULINT_UNDEFINED, &heap);
+
+		/* This is a leaf page in a clustered index. */
+
+		/* Check if there are any externally stored columns.
+		For each externally stored column, restore the
+		BTR_EXTERN_FIELD_REF separately. */
+
+		if (rec_offs_any_extern(offsets)) {
+			if (UNIV_UNLIKELY
+			    (!page_zip_decompress_clust_ext(
+				    d_stream, rec, offsets, trx_id_col))) {
+
+				goto zlib_error;
+			}
+		} else {
+			/* Skip trx_id and roll_ptr */
+			ulint	len;
+			byte*	dst = rec_get_nth_field(rec, offsets,
+							trx_id_col, &len);
+			if (UNIV_UNLIKELY(len < DATA_TRX_ID_LEN
+					  + DATA_ROLL_PTR_LEN)) {
+
+				page_zip_fail(("page_zip_decompress_clust:"
+					       " len = %lu\n", (ulong) len));
+				goto zlib_error;
+			}
+
+			d_stream->avail_out = static_cast<uInt>(
+				dst - d_stream->next_out);
+
+			switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+			case Z_STREAM_END:
+			case Z_OK:
+			case Z_BUF_ERROR:
+				if (!d_stream->avail_out) {
+					break;
+				}
+				/* fall through */
+			default:
+				page_zip_fail(("page_zip_decompress_clust:"
+					       " 2 inflate(Z_SYNC_FLUSH)=%s\n",
+					       d_stream->msg));
+				goto zlib_error;
+			}
+
+			ut_ad(d_stream->next_out == dst);
+
+			/* Clear DB_TRX_ID and DB_ROLL_PTR in order to
+			avoid uninitialized bytes in case the record
+			is affected by page_zip_apply_log(). */
+			memset(dst, 0, DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+			d_stream->next_out += DATA_TRX_ID_LEN
+				+ DATA_ROLL_PTR_LEN;
+		}
+
+		/* Decompress the last bytes of the record. */
+		d_stream->avail_out = static_cast<uInt>(
+			rec_get_end(rec, offsets) - d_stream->next_out);
+
+		switch (inflate(d_stream, Z_SYNC_FLUSH)) {
+		case Z_STREAM_END:
+		case Z_OK:
+		case Z_BUF_ERROR:
+			if (!d_stream->avail_out) {
+				break;
+			}
+			/* fall through */
+		default:
+			page_zip_fail(("page_zip_decompress_clust:"
+				       " 3 inflate(Z_SYNC_FLUSH)=%s\n",
+				       d_stream->msg));
+			goto zlib_error;
+		}
+	}
+
+	/* Decompress any trailing garbage, in case the last record was
+	allocated from an originally longer space on the free list. */
+	d_stream->avail_out = static_cast<uInt>(
+		page_header_get_field(page_zip->data, PAGE_HEAP_TOP)
+		- page_offset(d_stream->next_out));
+	if (UNIV_UNLIKELY(d_stream->avail_out > srv_page_size
+			  - PAGE_ZIP_START - PAGE_DIR)) {
+
+		page_zip_fail(("page_zip_decompress_clust:"
+			       " avail_out = %u\n",
+			       d_stream->avail_out));
+		goto zlib_error;
+	}
+
+	if (UNIV_UNLIKELY(inflate(d_stream, Z_FINISH) != Z_STREAM_END)) {
+		page_zip_fail(("page_zip_decompress_clust:"
+			       " inflate(Z_FINISH)=%s\n",
+			       d_stream->msg));
+zlib_error:
+		inflateEnd(d_stream);
+		return(FALSE);
+	}
+
+	/* Note that d_stream->avail_out > 0 may hold here
+	if the modification log is nonempty. */
+
+zlib_done:
+	if (UNIV_UNLIKELY(inflateEnd(d_stream) != Z_OK)) {
+		ut_error;
+	}
+
+	{
+		page_t*	page = page_align(d_stream->next_out);
+
+		/* Clear the unused heap space on the uncompressed page. */
+		memset(d_stream->next_out, 0,
+		       ulint(page_dir_get_nth_slot(page,
+						   page_dir_get_n_slots(page)
+						   - 1U)
+			     - d_stream->next_out));
+	}
+
+	ut_d(page_zip->m_start = uint16_t(PAGE_DATA + d_stream->total_in));
+
+	/* Apply the modification log. */
+	{
+		const byte*	mod_log_ptr;
+		mod_log_ptr = page_zip_apply_log(d_stream->next_in,
+						 d_stream->avail_in + 1,
+						 recs, n_dense,
+						 index->n_fields,
+						 trx_id_col, heap_status,
+						 index, offsets);
+
+		if (UNIV_UNLIKELY(!mod_log_ptr)) {
+			return(FALSE);
+		}
+		page_zip->m_end = uint16_t(mod_log_ptr - page_zip->data);
+		page_zip->m_nonempty = mod_log_ptr != d_stream->next_in;
+	}
+
+	if (UNIV_UNLIKELY(page_zip_get_trailer_len(page_zip, TRUE)
+			  + page_zip->m_end >= page_zip_get_size(page_zip))) {
+
+		page_zip_fail(("page_zip_decompress_clust: %lu + %lu >= %lu\n",
+			       (ulong) page_zip_get_trailer_len(
+				       page_zip, TRUE),
+			       (ulong) page_zip->m_end,
+			       (ulong) page_zip_get_size(page_zip)));
+		return(FALSE);
+	}
+
+	storage = page_zip_dir_start_low(page_zip, n_dense);
+
+	externs = storage - n_dense
+		* (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+	/* Restore the uncompressed columns in heap_no order. */
+
+	for (slot = 0; slot < n_dense; slot++) {
+		ulint	i;
+		ulint	len;
+		byte*	dst;
+		rec_t*	rec	= recs[slot];
+		bool	exists	= !page_zip_dir_find_free(
+			page_zip, page_offset(rec));
+		offsets = rec_get_offsets(rec, index, offsets, index->n_fields,
+					  ULINT_UNDEFINED, &heap);
+
+		dst = rec_get_nth_field(rec, offsets,
+					trx_id_col, &len);
+		ut_ad(len >= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+		storage -= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+		memcpy(dst, storage,
+		       DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+		/* Check if there are any externally stored
+		columns in this record.  For each externally
+		stored column, restore or clear the
+		BTR_EXTERN_FIELD_REF. */
+		if (!rec_offs_any_extern(offsets)) {
+			continue;
+		}
+
+		for (i = 0; i < rec_offs_n_fields(offsets); i++) {
+			if (!rec_offs_nth_extern(offsets, i)) {
+				continue;
+			}
+			dst = rec_get_nth_field(rec, offsets, i, &len);
+
+			if (UNIV_UNLIKELY(len < BTR_EXTERN_FIELD_REF_SIZE)) {
+				page_zip_fail(("page_zip_decompress_clust:"
+					       " %lu < 20\n",
+					       (ulong) len));
+				return(FALSE);
+			}
+
+			dst += len - BTR_EXTERN_FIELD_REF_SIZE;
+
+			if (UNIV_LIKELY(exists)) {
+				/* Existing record:
+				restore the BLOB pointer */
+				externs -= BTR_EXTERN_FIELD_REF_SIZE;
+
+				if (UNIV_UNLIKELY
+				    (externs < page_zip->data
+				     + page_zip->m_end)) {
+					page_zip_fail(("page_zip_"
+						       "decompress_clust:"
+						       " %p < %p + %lu\n",
+						       (const void*) externs,
+						       (const void*)
+						       page_zip->data,
+						       (ulong)
+						       page_zip->m_end));
+					return(FALSE);
+				}
+
+				memcpy(dst, externs,
+				       BTR_EXTERN_FIELD_REF_SIZE);
+
+				page_zip->n_blobs++;
+			} else {
+				/* Deleted record:
+				clear the BLOB pointer */
+				memset(dst, 0,
+				       BTR_EXTERN_FIELD_REF_SIZE);
+			}
+		}
+	}
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Decompress a page.  This function should tolerate errors on the compressed
+page.  Instead of letting assertions fail, it will return FALSE if an
+inconsistency is detected.
+@return TRUE on success, FALSE on failure */
+static
+ibool
+page_zip_decompress_low(
+/*====================*/
+	page_zip_des_t*	page_zip,/*!< in: data, ssize;
+				out: m_start, m_end, m_nonempty, n_blobs */
+	page_t*		page,	/*!< out: uncompressed page, may be trashed */
+	ibool		all)	/*!< in: TRUE=decompress the whole page;
+				FALSE=verify but do not copy some
+				page header fields that should not change
+				after page creation */
+{
+	z_stream	d_stream;
+	dict_index_t*	index	= NULL;
+	rec_t**		recs;	/*!< dense page directory, sorted by address */
+	ulint		n_dense;/* number of user records on the page */
+	ulint		trx_id_col = ULINT_UNDEFINED;
+	mem_heap_t*	heap;
+	rec_offs*	offsets;
+
+	ut_ad(page_zip_simple_validate(page_zip));
+	MEM_CHECK_ADDRESSABLE(page, srv_page_size);
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+
+	/* The dense directory excludes the infimum and supremum records. */
+	n_dense = page_dir_get_n_heap(page_zip->data) - PAGE_HEAP_NO_USER_LOW;
+	if (UNIV_UNLIKELY(n_dense * PAGE_ZIP_DIR_SLOT_SIZE
+			  >= page_zip_get_size(page_zip))) {
+		page_zip_fail(("page_zip_decompress 1: %lu %lu\n",
+			       (ulong) n_dense,
+			       (ulong) page_zip_get_size(page_zip)));
+		return(FALSE);
+	}
+
+	heap = mem_heap_create(n_dense * (3 * sizeof *recs) + srv_page_size);
+
+	recs = static_cast<rec_t**>(
+		mem_heap_alloc(heap, n_dense * sizeof *recs));
+
+	if (all) {
+		/* Copy the page header. */
+		memcpy_aligned<2>(page, page_zip->data, PAGE_DATA);
+	} else {
+		/* Check that the bytes that we skip are identical. */
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+		ut_a(!memcmp(FIL_PAGE_TYPE + page,
+			     FIL_PAGE_TYPE + page_zip->data,
+			     PAGE_HEADER - FIL_PAGE_TYPE));
+		ut_a(!memcmp(PAGE_HEADER + PAGE_LEVEL + page,
+			     PAGE_HEADER + PAGE_LEVEL + page_zip->data,
+			     PAGE_DATA - (PAGE_HEADER + PAGE_LEVEL)));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+
+		/* Copy the mutable parts of the page header. */
+		memcpy_aligned<8>(page, page_zip->data, FIL_PAGE_TYPE);
+		memcpy_aligned<2>(PAGE_HEADER + page,
+				  PAGE_HEADER + page_zip->data,
+				  PAGE_LEVEL - PAGE_N_DIR_SLOTS);
+
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+		/* Check that the page headers match after copying. */
+		ut_a(!memcmp(page, page_zip->data, PAGE_DATA));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+	}
+
+#ifdef UNIV_ZIP_DEBUG
+	/* Clear the uncompressed page, except the header. */
+	memset(PAGE_DATA + page, 0x55, srv_page_size - PAGE_DATA);
+#endif /* UNIV_ZIP_DEBUG */
+	MEM_UNDEFINED(PAGE_DATA + page, srv_page_size - PAGE_DATA);
+
+	/* Copy the page directory. */
+	if (UNIV_UNLIKELY(!page_zip_dir_decode(page_zip, page, recs,
+					       n_dense))) {
+zlib_error:
+		mem_heap_free(heap);
+		return(FALSE);
+	}
+
+	/* Copy the infimum and supremum records. */
+	memcpy(page + (PAGE_NEW_INFIMUM - REC_N_NEW_EXTRA_BYTES),
+	       infimum_extra, sizeof infimum_extra);
+	if (page_is_empty(page)) {
+		rec_set_next_offs_new(page + PAGE_NEW_INFIMUM,
+				      PAGE_NEW_SUPREMUM);
+	} else {
+		rec_set_next_offs_new(page + PAGE_NEW_INFIMUM,
+				      page_zip_dir_get(page_zip, 0)
+				      & PAGE_ZIP_DIR_SLOT_MASK);
+	}
+	memcpy(page + PAGE_NEW_INFIMUM, infimum_data, sizeof infimum_data);
+	memcpy_aligned<4>(PAGE_NEW_SUPREMUM - REC_N_NEW_EXTRA_BYTES + 1
+			  + page, supremum_extra_data,
+			  sizeof supremum_extra_data);
+
+	page_zip_set_alloc(&d_stream, heap);
+
+	d_stream.next_in = page_zip->data + PAGE_DATA;
+	/* Subtract the space reserved for
+	the page header and the end marker of the modification log. */
+	d_stream.avail_in = static_cast<uInt>(
+		page_zip_get_size(page_zip) - (PAGE_DATA + 1));
+	d_stream.next_out = page + PAGE_ZIP_START;
+	d_stream.avail_out = uInt(srv_page_size - PAGE_ZIP_START);
+
+	if (UNIV_UNLIKELY(inflateInit2(&d_stream, int(srv_page_size_shift))
+			  != Z_OK)) {
+		ut_error;
+	}
+
+	/* Decode the zlib header and the index information. */
+	if (UNIV_UNLIKELY(inflate(&d_stream, Z_BLOCK) != Z_OK)) {
+
+		page_zip_fail(("page_zip_decompress:"
+			       " 1 inflate(Z_BLOCK)=%s\n", d_stream.msg));
+		goto zlib_error;
+	}
+
+	if (UNIV_UNLIKELY(inflate(&d_stream, Z_BLOCK) != Z_OK)) {
+
+		page_zip_fail(("page_zip_decompress:"
+			       " 2 inflate(Z_BLOCK)=%s\n", d_stream.msg));
+		goto zlib_error;
+	}
+
+	index = page_zip_fields_decode(
+		page + PAGE_ZIP_START, d_stream.next_out,
+		page_is_leaf(page) ? &trx_id_col : NULL,
+		fil_page_get_type(page) == FIL_PAGE_RTREE);
+
+	if (UNIV_UNLIKELY(!index)) {
+
+		goto zlib_error;
+	}
+
+	/* Decompress the user records. */
+	page_zip->n_blobs = 0;
+	d_stream.next_out = page + PAGE_ZIP_START;
+
+	{
+		/* Pre-allocate the offsets for rec_get_offsets_reverse(). */
+		ulint	n = 1 + 1/* node ptr */ + REC_OFFS_HEADER_SIZE
+			+ dict_index_get_n_fields(index);
+
+		offsets = static_cast<rec_offs*>(
+			mem_heap_alloc(heap, n * sizeof(ulint)));
+
+		rec_offs_set_n_alloc(offsets, n);
+	}
+
+	/* Decompress the records in heap_no order. */
+	if (!page_is_leaf(page)) {
+		/* This is a node pointer page. */
+		ulint	info_bits;
+
+		if (UNIV_UNLIKELY
+		    (!page_zip_decompress_node_ptrs(page_zip, &d_stream,
+						    recs, n_dense, index,
+						    offsets, heap))) {
+			goto err_exit;
+		}
+
+		info_bits = page_has_prev(page) ? 0 : REC_INFO_MIN_REC_FLAG;
+
+		if (UNIV_UNLIKELY(!page_zip_set_extra_bytes(page_zip, page,
+							    info_bits))) {
+			goto err_exit;
+		}
+	} else if (UNIV_LIKELY(trx_id_col == ULINT_UNDEFINED)) {
+		/* This is a leaf page in a secondary index. */
+		if (UNIV_UNLIKELY(!page_zip_decompress_sec(page_zip, &d_stream,
+							   recs, n_dense,
+							   index, offsets))) {
+			goto err_exit;
+		}
+
+		if (UNIV_UNLIKELY(!page_zip_set_extra_bytes(page_zip,
+							    page, 0))) {
+err_exit:
+			page_zip_fields_free(index);
+			mem_heap_free(heap);
+			return(FALSE);
+		}
+	} else {
+		/* This is a leaf page in a clustered index. */
+		if (UNIV_UNLIKELY(!page_zip_decompress_clust(page_zip,
+							     &d_stream, recs,
+							     n_dense, index,
+							     trx_id_col,
+							     offsets, heap))) {
+			goto err_exit;
+		}
+
+		if (UNIV_UNLIKELY(!page_zip_set_extra_bytes(page_zip,
+							    page, 0))) {
+			goto err_exit;
+		}
+	}
+
+	ut_a(page_is_comp(page));
+	MEM_CHECK_DEFINED(page, srv_page_size);
+
+	page_zip_fields_free(index);
+	mem_heap_free(heap);
+
+	return(TRUE);
+}
+
+/**********************************************************************//**
+Decompress a page.  This function should tolerate errors on the compressed
+page.  Instead of letting assertions fail, it will return FALSE if an
+inconsistency is detected.
+@return TRUE on success, FALSE on failure */
+ibool
+page_zip_decompress(
+/*================*/
+	page_zip_des_t*	page_zip,/*!< in: data, ssize;
+				out: m_start, m_end, m_nonempty, n_blobs */
+	page_t*		page,	/*!< out: uncompressed page, may be trashed */
+	ibool		all)	/*!< in: TRUE=decompress the whole page;
+				FALSE=verify but do not copy some
+				page header fields that should not change
+				after page creation */
+{
+	const ulonglong ns = my_interval_timer();
+
+	if (!page_zip_decompress_low(page_zip, page, all)) {
+		return(FALSE);
+	}
+
+	const uint64_t time_diff = (my_interval_timer() - ns) / 1000;
+	page_zip_stat[page_zip->ssize - 1].decompressed++;
+	page_zip_stat[page_zip->ssize - 1].decompressed_usec += time_diff;
+
+	index_id_t	index_id = btr_page_get_index_id(page);
+
+	if (srv_cmp_per_index_enabled) {
+		mysql_mutex_lock(&page_zip_stat_per_index_mutex);
+		page_zip_stat_per_index[index_id].decompressed++;
+		page_zip_stat_per_index[index_id].decompressed_usec += time_diff;
+		mysql_mutex_unlock(&page_zip_stat_per_index_mutex);
+	}
+
+	/* Update the stat counter for LRU policy. */
+	buf_LRU_stat_inc_unzip();
+
+	MONITOR_INC(MONITOR_PAGE_DECOMPRESS);
+
+	return(TRUE);
+}
+
+#ifdef UNIV_ZIP_DEBUG
+/**********************************************************************//**
+Dump a block of memory on the standard error stream. */
+static
+void
+page_zip_hexdump_func(
+/*==================*/
+	const char*	name,	/*!< in: name of the data structure */
+	const void*	buf,	/*!< in: data */
+	ulint		size)	/*!< in: length of the data, in bytes */
+{
+	const byte*	s	= static_cast<const byte*>(buf);
+	ulint		addr;
+	const ulint	width	= 32; /* bytes per line */
+
+	fprintf(stderr, "%s:\n", name);
+
+	for (addr = 0; addr < size; addr += width) {
+		ulint	i;
+
+		fprintf(stderr, "%04lx ", (ulong) addr);
+
+		i = ut_min(width, size - addr);
+
+		while (i--) {
+			fprintf(stderr, "%02x", *s++);
+		}
+
+		putc('\n', stderr);
+	}
+}
+
+/** Dump a block of memory on the standard error stream.
+@param buf in: data
+@param size in: length of the data, in bytes */
+#define page_zip_hexdump(buf, size) page_zip_hexdump_func(#buf, buf, size)
+
+/** Flag: make page_zip_validate() compare page headers only */
+bool	page_zip_validate_header_only;
+
+/**********************************************************************//**
+Check that the compressed and decompressed pages match.
+@return TRUE if valid, FALSE if not */
+ibool
+page_zip_validate_low(
+/*==================*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	const page_t*		page,	/*!< in: uncompressed page */
+	const dict_index_t*	index,	/*!< in: index of the page, if known */
+	ibool			sloppy)	/*!< in: FALSE=strict,
+					TRUE=ignore the MIN_REC_FLAG */
+{
+	page_zip_des_t	temp_page_zip;
+	ibool		valid;
+
+	if (memcmp(page_zip->data + FIL_PAGE_PREV, page + FIL_PAGE_PREV,
+		   FIL_PAGE_LSN - FIL_PAGE_PREV)
+	    || memcmp(page_zip->data + FIL_PAGE_TYPE, page + FIL_PAGE_TYPE, 2)
+	    || memcmp(page_zip->data + FIL_PAGE_DATA, page + FIL_PAGE_DATA,
+		      PAGE_ROOT_AUTO_INC)
+	    /* The PAGE_ROOT_AUTO_INC can be updated while holding an SX-latch
+	    on the clustered index root page (page number 3 in .ibd files).
+	    That allows concurrent readers (holding buf_block_t::lock S-latch).
+	    Because we do not know what type of a latch our caller is holding,
+	    we will ignore the field on clustered index root pages in order
+	    to avoid false positives. */
+	    || (page_get_page_no(page) != 3/* clustered index root page */
+		&& memcmp(&page_zip->data[FIL_PAGE_DATA + PAGE_ROOT_AUTO_INC],
+			  &page[FIL_PAGE_DATA + PAGE_ROOT_AUTO_INC], 8))
+	    || memcmp(&page_zip->data[FIL_PAGE_DATA + PAGE_HEADER_PRIV_END],
+		      &page[FIL_PAGE_DATA + PAGE_HEADER_PRIV_END],
+		      PAGE_DATA - FIL_PAGE_DATA - PAGE_HEADER_PRIV_END)) {
+		page_zip_fail(("page_zip_validate: page header\n"));
+		page_zip_hexdump(page_zip, sizeof *page_zip);
+		page_zip_hexdump(page_zip->data, page_zip_get_size(page_zip));
+		page_zip_hexdump(page, srv_page_size);
+		return(FALSE);
+	}
+
+	ut_a(page_is_comp(page));
+
+	if (page_zip_validate_header_only) {
+		return(TRUE);
+	}
+
+	/* page_zip_decompress() expects the uncompressed page to be
+	srv_page_size aligned. */
+	page_t* temp_page = static_cast<byte*>(aligned_malloc(srv_page_size,
+							      srv_page_size));
+
+	MEM_CHECK_DEFINED(page, srv_page_size);
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+
+	temp_page_zip = *page_zip;
+	valid = page_zip_decompress_low(&temp_page_zip, temp_page, TRUE);
+	if (!valid) {
+		fputs("page_zip_validate(): failed to decompress\n", stderr);
+		goto func_exit;
+	}
+	if (page_zip->n_blobs != temp_page_zip.n_blobs) {
+		page_zip_fail(("page_zip_validate: n_blobs: %u!=%u\n",
+			       page_zip->n_blobs, temp_page_zip.n_blobs));
+		valid = FALSE;
+	}
+#ifdef UNIV_DEBUG
+	if (page_zip->m_start != temp_page_zip.m_start) {
+		page_zip_fail(("page_zip_validate: m_start: %u!=%u\n",
+			       page_zip->m_start, temp_page_zip.m_start));
+		valid = FALSE;
+	}
+#endif /* UNIV_DEBUG */
+	if (page_zip->m_end != temp_page_zip.m_end) {
+		page_zip_fail(("page_zip_validate: m_end: %u!=%u\n",
+			       page_zip->m_end, temp_page_zip.m_end));
+		valid = FALSE;
+	}
+	if (page_zip->m_nonempty != temp_page_zip.m_nonempty) {
+		page_zip_fail(("page_zip_validate(): m_nonempty: %u!=%u\n",
+			       page_zip->m_nonempty,
+			       temp_page_zip.m_nonempty));
+		valid = FALSE;
+	}
+	if (memcmp(page + PAGE_HEADER, temp_page + PAGE_HEADER,
+		   srv_page_size - PAGE_HEADER - FIL_PAGE_DATA_END)) {
+
+		/* In crash recovery, the "minimum record" flag may be
+		set incorrectly until the mini-transaction is
+		committed.  Let us tolerate that difference when we
+		are performing a sloppy validation. */
+
+		rec_offs*	offsets;
+		mem_heap_t*	heap;
+		const rec_t*	rec;
+		const rec_t*	trec;
+		byte		info_bits_diff;
+		ulint		offset
+			= rec_get_next_offs(page + PAGE_NEW_INFIMUM, TRUE);
+		ut_a(offset >= PAGE_NEW_SUPREMUM);
+		offset -= 5/*REC_NEW_INFO_BITS*/;
+
+		info_bits_diff = page[offset] ^ temp_page[offset];
+
+		if (info_bits_diff == REC_INFO_MIN_REC_FLAG) {
+			temp_page[offset] = page[offset];
+
+			if (!memcmp(page + PAGE_HEADER,
+				    temp_page + PAGE_HEADER,
+				    srv_page_size - PAGE_HEADER
+				    - FIL_PAGE_DATA_END)) {
+
+				/* Only the minimum record flag
+				differed.  Let us ignore it. */
+				page_zip_fail(("page_zip_validate:"
+					       " min_rec_flag"
+					       " (%s" UINT32PF "," UINT32PF
+					       ",0x%02x)\n",
+					       sloppy ? "ignored, " : "",
+					       page_get_space_id(page),
+					       page_get_page_no(page),
+					       page[offset]));
+				/* We don't check for spatial index, since
+				the "minimum record" could be deleted when
+				doing rtr_update_mbr_field.
+				GIS_FIXME: need to validate why
+				rtr_update_mbr_field.() could affect this */
+				if (index && dict_index_is_spatial(index)) {
+					valid = true;
+				} else {
+					valid = sloppy;
+				}
+				goto func_exit;
+			}
+		}
+
+		/* Compare the pointers in the PAGE_FREE list. */
+		rec = page_header_get_ptr(page, PAGE_FREE);
+		trec = page_header_get_ptr(temp_page, PAGE_FREE);
+
+		while (rec || trec) {
+			if (page_offset(rec) != page_offset(trec)) {
+				page_zip_fail(("page_zip_validate:"
+					       " PAGE_FREE list: %u!=%u\n",
+					       (unsigned) page_offset(rec),
+					       (unsigned) page_offset(trec)));
+				valid = FALSE;
+				goto func_exit;
+			}
+
+			rec = page_rec_get_next_low(rec, TRUE);
+			trec = page_rec_get_next_low(trec, TRUE);
+		}
+
+		/* Compare the records. */
+		heap = NULL;
+		offsets = NULL;
+		rec = page_rec_get_next_low(
+			page + PAGE_NEW_INFIMUM, TRUE);
+		trec = page_rec_get_next_low(
+			temp_page + PAGE_NEW_INFIMUM, TRUE);
+		const ulint n_core = (index && page_is_leaf(page))
+			? index->n_fields : 0;
+
+		do {
+			if (page_offset(rec) != page_offset(trec)) {
+				page_zip_fail(("page_zip_validate:"
+					       " record list: 0x%02x!=0x%02x\n",
+					       (unsigned) page_offset(rec),
+					       (unsigned) page_offset(trec)));
+				valid = FALSE;
+				break;
+			}
+
+			if (index) {
+				/* Compare the data. */
+				offsets = rec_get_offsets(
+					rec, index, offsets, n_core,
+					ULINT_UNDEFINED, &heap);
+
+				if (memcmp(rec - rec_offs_extra_size(offsets),
+					   trec - rec_offs_extra_size(offsets),
+					   rec_offs_size(offsets))) {
+					page_zip_fail(
+						("page_zip_validate:"
+						 " record content: 0x%02x",
+						 (unsigned) page_offset(rec)));
+					valid = FALSE;
+					break;
+				}
+			}
+
+			rec = page_rec_get_next_low(rec, TRUE);
+			trec = page_rec_get_next_low(trec, TRUE);
+		} while (rec || trec);
+
+		if (heap) {
+			mem_heap_free(heap);
+		}
+	}
+
+func_exit:
+	if (!valid) {
+		page_zip_hexdump(page_zip, sizeof *page_zip);
+		page_zip_hexdump(page_zip->data, page_zip_get_size(page_zip));
+		page_zip_hexdump(page, srv_page_size);
+		page_zip_hexdump(temp_page, srv_page_size);
+	}
+	aligned_free(temp_page);
+	return(valid);
+}
+
+/**********************************************************************//**
+Check that the compressed and decompressed pages match.
+@return TRUE if valid, FALSE if not */
+ibool
+page_zip_validate(
+/*==============*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	const page_t*		page,	/*!< in: uncompressed page */
+	const dict_index_t*	index)	/*!< in: index of the page, if known */
+{
+	return(page_zip_validate_low(page_zip, page, index,
+				     recv_recovery_is_on()));
+}
+#endif /* UNIV_ZIP_DEBUG */
+
+#ifdef UNIV_DEBUG
+/**********************************************************************//**
+Assert that the compressed and decompressed page headers match.
+@return TRUE */
+static
+ibool
+page_zip_header_cmp(
+/*================*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	const byte*		page)	/*!< in: uncompressed page */
+{
+	ut_ad(!memcmp(page_zip->data + FIL_PAGE_PREV, page + FIL_PAGE_PREV,
+		      FIL_PAGE_LSN - FIL_PAGE_PREV));
+	ut_ad(!memcmp(page_zip->data + FIL_PAGE_TYPE, page + FIL_PAGE_TYPE,
+		      2));
+	ut_ad(!memcmp(page_zip->data + FIL_PAGE_DATA, page + FIL_PAGE_DATA,
+		      PAGE_DATA - FIL_PAGE_DATA));
+
+	return(TRUE);
+}
+#endif /* UNIV_DEBUG */
+
+/**********************************************************************//**
+Write a record on the compressed page that contains externally stored
+columns.  The data must already have been written to the uncompressed page.
+@return end of modification log */
+static
+byte*
+page_zip_write_rec_ext(
+/*===================*/
+	buf_block_t*	block,		/*!< in/out: compressed page */
+	const byte*	rec,		/*!< in: record being written */
+	const dict_index_t*index,	/*!< in: record descriptor */
+	const rec_offs*	offsets,	/*!< in: rec_get_offsets(rec, index) */
+	ulint		create,		/*!< in: nonzero=insert, zero=update */
+	ulint		trx_id_col,	/*!< in: position of DB_TRX_ID */
+	ulint		heap_no,	/*!< in: heap number of rec */
+	byte*		storage,	/*!< in: end of dense page directory */
+	byte*		data,		/*!< in: end of modification log */
+	mtr_t*		mtr)		/*!< in/out: mini-transaction */
+{
+	const byte*	start	= rec;
+	ulint		i;
+	ulint		len;
+	byte*		externs	= storage;
+	ulint		n_ext	= rec_offs_n_extern(offsets);
+	const page_t* const page = block->page.frame;
+	page_zip_des_t* const page_zip = &block->page.zip;
+
+	ut_ad(rec_offs_validate(rec, index, offsets));
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+
+	externs -= (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN)
+		* (page_dir_get_n_heap(page) - PAGE_HEAP_NO_USER_LOW);
+
+	/* Note that this will not take into account
+	the BLOB columns of rec if create==TRUE. */
+	ut_ad(data + rec_offs_data_size(offsets)
+	      - (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN)
+	      - n_ext * FIELD_REF_SIZE
+	      < externs - FIELD_REF_SIZE * page_zip->n_blobs);
+
+	if (n_ext) {
+		ulint	blob_no = page_zip_get_n_prev_extern(
+			page_zip, rec, index);
+		byte*	ext_end = externs - page_zip->n_blobs * FIELD_REF_SIZE;
+		ut_ad(blob_no <= page_zip->n_blobs);
+		externs -= blob_no * FIELD_REF_SIZE;
+
+		if (create) {
+			page_zip->n_blobs = (page_zip->n_blobs + n_ext)
+				& ((1U << 12) - 1);
+			ASSERT_ZERO_BLOB(ext_end - n_ext * FIELD_REF_SIZE);
+			if (ulint len = ulint(externs - ext_end)) {
+				byte* ext_start = ext_end
+					- n_ext * FIELD_REF_SIZE;
+				memmove(ext_start, ext_end, len);
+				mtr->memmove(*block,
+					     ext_start - page_zip->data,
+					     ext_end - page_zip->data, len);
+			}
+		}
+
+		ut_a(blob_no + n_ext <= page_zip->n_blobs);
+	}
+
+	for (i = 0; i < rec_offs_n_fields(offsets); i++) {
+		const byte*	src;
+
+		if (UNIV_UNLIKELY(i == trx_id_col)) {
+			ut_ad(!rec_offs_nth_extern(offsets,
+						   i));
+			ut_ad(!rec_offs_nth_extern(offsets,
+						   i + 1));
+			/* Locate trx_id and roll_ptr. */
+			src = rec_get_nth_field(rec, offsets,
+						i, &len);
+			ut_ad(len == DATA_TRX_ID_LEN);
+			ut_ad(src + DATA_TRX_ID_LEN
+			      == rec_get_nth_field(
+				      rec, offsets,
+				      i + 1, &len));
+			ut_ad(len == DATA_ROLL_PTR_LEN);
+
+			/* Log the preceding fields. */
+			ASSERT_ZERO(data, src - start);
+			memcpy(data, start, ulint(src - start));
+			data += src - start;
+			start = src + (DATA_TRX_ID_LEN
+				       + DATA_ROLL_PTR_LEN);
+
+			/* Store trx_id and roll_ptr. */
+			constexpr ulint sys_len = DATA_TRX_ID_LEN
+				+ DATA_ROLL_PTR_LEN;
+			byte* sys = storage - sys_len * (heap_no - 1);
+			memcpy(sys, src, sys_len);
+			i++; /* skip also roll_ptr */
+			mtr->zmemcpy(*block, sys - page_zip->data, sys_len);
+		} else if (rec_offs_nth_extern(offsets, i)) {
+			src = rec_get_nth_field(rec, offsets,
+						i, &len);
+
+			ut_ad(dict_index_is_clust(index));
+			ut_ad(len >= FIELD_REF_SIZE);
+			src += len - FIELD_REF_SIZE;
+
+			ASSERT_ZERO(data, src - start);
+			memcpy(data, start, ulint(src - start));
+			data += src - start;
+			start = src + FIELD_REF_SIZE;
+
+			/* Store the BLOB pointer. */
+			externs -= FIELD_REF_SIZE;
+			ut_ad(data < externs);
+			memcpy(externs, src, FIELD_REF_SIZE);
+			mtr->zmemcpy(*block, externs - page_zip->data,
+				     FIELD_REF_SIZE);
+		}
+	}
+
+	/* Log the last bytes of the record. */
+	len = rec_offs_data_size(offsets) - ulint(start - rec);
+
+	ASSERT_ZERO(data, len);
+	memcpy(data, start, len);
+	data += len;
+
+	return(data);
+}
+
+/** Write an entire record to the ROW_FORMAT=COMPRESSED page.
+The data must already have been written to the uncompressed page.
+@param[in,out]	block		ROW_FORMAT=COMPRESSED page
+@param[in]	rec		record in the uncompressed page
+@param[in]	index		the index that the page belongs to
+@param[in]	offsets		rec_get_offsets(rec, index)
+@param[in]	create		nonzero=insert, zero=update
+@param[in,out]	mtr		mini-transaction */
+void page_zip_write_rec(buf_block_t *block, const byte *rec,
+                        const dict_index_t *index, const rec_offs *offsets,
+                        ulint create, mtr_t *mtr)
+{
+	const page_t* const page = block->page.frame;
+	page_zip_des_t* const page_zip = &block->page.zip;
+	byte*		data;
+	byte*		storage;
+	ulint		heap_no;
+	byte*		slot;
+
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(page_zip_get_size(page_zip)
+	      > PAGE_DATA + page_zip_dir_size(page_zip));
+	ut_ad(rec_offs_comp(offsets));
+	ut_ad(rec_offs_validate(rec, index, offsets));
+
+	ut_ad(page_zip->m_start >= PAGE_DATA);
+
+	ut_ad(page_zip_header_cmp(page_zip, page));
+	ut_ad(page_simple_validate_new((page_t*) page));
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+
+	slot = page_zip_dir_find(page_zip, page_offset(rec));
+	ut_a(slot);
+	byte s = *slot;
+	/* Copy the delete mark. */
+	if (rec_get_deleted_flag(rec, TRUE)) {
+		/* In delete-marked records, DB_TRX_ID must
+		always refer to an existing undo log record.
+		On non-leaf pages, the delete-mark flag is garbage. */
+		ut_ad(!index->is_primary() || !page_is_leaf(page)
+		      || row_get_rec_trx_id(rec, index, offsets));
+		s |= PAGE_ZIP_DIR_SLOT_DEL >> 8;
+	} else {
+		s &= byte(~(PAGE_ZIP_DIR_SLOT_DEL >> 8));
+	}
+
+	if (s != *slot) {
+		*slot = s;
+		mtr->zmemcpy(*block, slot - page_zip->data, 1);
+	}
+
+	ut_ad(rec_get_start((rec_t*) rec, offsets) >= page + PAGE_ZIP_START);
+	ut_ad(rec_get_end((rec_t*) rec, offsets) <= page + srv_page_size
+	      - PAGE_DIR - PAGE_DIR_SLOT_SIZE
+	      * page_dir_get_n_slots(page));
+
+	heap_no = rec_get_heap_no_new(rec);
+	ut_ad(heap_no >= PAGE_HEAP_NO_USER_LOW); /* not infimum or supremum */
+	ut_ad(heap_no < page_dir_get_n_heap(page));
+
+	/* Append to the modification log. */
+	data = page_zip->data + page_zip->m_end;
+	ut_ad(!*data);
+
+	/* Identify the record by writing its heap number - 1.
+	0 is reserved to indicate the end of the modification log. */
+
+	if (UNIV_UNLIKELY(heap_no - 1 >= 64)) {
+		*data++ = (byte) (0x80 | (heap_no - 1) >> 7);
+		ut_ad(!*data);
+	}
+	*data++ = (byte) ((heap_no - 1) << 1);
+	ut_ad(!*data);
+
+	{
+		const byte*	start	= rec - rec_offs_extra_size(offsets);
+		const byte*	b	= rec - REC_N_NEW_EXTRA_BYTES;
+
+		/* Write the extra bytes backwards, so that
+		rec_offs_extra_size() can be easily computed in
+		page_zip_apply_log() by invoking
+		rec_get_offsets_reverse(). */
+
+		while (b != start) {
+			*data++ = *--b;
+			ut_ad(!*data);
+		}
+	}
+
+	/* Write the data bytes.  Store the uncompressed bytes separately. */
+	storage = page_zip_dir_start(page_zip);
+
+	if (page_is_leaf(page)) {
+		if (dict_index_is_clust(index)) {
+			/* Store separately trx_id, roll_ptr and
+			the BTR_EXTERN_FIELD_REF of each BLOB column. */
+			if (rec_offs_any_extern(offsets)) {
+				data = page_zip_write_rec_ext(
+					block,
+					rec, index, offsets, create,
+					index->db_trx_id(), heap_no,
+					storage, data, mtr);
+			} else {
+				/* Locate trx_id and roll_ptr. */
+				ulint len;
+				const byte*	src
+					= rec_get_nth_field(rec, offsets,
+							    index->db_trx_id(),
+							    &len);
+				ut_ad(len == DATA_TRX_ID_LEN);
+				ut_ad(src + DATA_TRX_ID_LEN
+				      == rec_get_nth_field(
+					      rec, offsets,
+					      index->db_roll_ptr(), &len));
+				ut_ad(len == DATA_ROLL_PTR_LEN);
+
+				/* Log the preceding fields. */
+				ASSERT_ZERO(data, src - rec);
+				memcpy(data, rec, ulint(src - rec));
+				data += src - rec;
+
+				/* Store trx_id and roll_ptr. */
+				constexpr ulint sys_len
+					= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+				byte* sys = storage - sys_len * (heap_no - 1);
+				memcpy(sys, src, sys_len);
+
+				src += sys_len;
+				mtr->zmemcpy(*block, sys - page_zip->data,
+					     sys_len);
+				/* Log the last bytes of the record. */
+				len = rec_offs_data_size(offsets)
+					- ulint(src - rec);
+
+				ASSERT_ZERO(data, len);
+				memcpy(data, src, len);
+				data += len;
+			}
+		} else {
+			/* Leaf page of a secondary index:
+			no externally stored columns */
+			ut_ad(!rec_offs_any_extern(offsets));
+
+			/* Log the entire record. */
+			ulint len = rec_offs_data_size(offsets);
+
+			ASSERT_ZERO(data, len);
+			memcpy(data, rec, len);
+			data += len;
+		}
+	} else {
+		/* This is a node pointer page. */
+		/* Non-leaf nodes should not have any externally
+		stored columns. */
+		ut_ad(!rec_offs_any_extern(offsets));
+
+		/* Copy the data bytes, except node_ptr. */
+		ulint len = rec_offs_data_size(offsets) - REC_NODE_PTR_SIZE;
+		ut_ad(data + len < storage - REC_NODE_PTR_SIZE
+		      * (page_dir_get_n_heap(page) - PAGE_HEAP_NO_USER_LOW));
+		ASSERT_ZERO(data, len);
+		memcpy(data, rec, len);
+		data += len;
+
+		/* Copy the node pointer to the uncompressed area. */
+		byte* node_ptr = storage - REC_NODE_PTR_SIZE * (heap_no - 1);
+		mtr->zmemcpy<mtr_t::MAYBE_NOP>(*block, node_ptr,
+					       rec + len, REC_NODE_PTR_SIZE);
+	}
+
+	ut_a(!*data);
+	ut_ad((ulint) (data - page_zip->data) < page_zip_get_size(page_zip));
+	mtr->zmemcpy(*block, page_zip->m_end,
+		     data - page_zip->data - page_zip->m_end);
+	page_zip->m_end = uint16_t(data - page_zip->data);
+	page_zip->m_nonempty = TRUE;
+
+#ifdef UNIV_ZIP_DEBUG
+	ut_a(page_zip_validate(page_zip, page_align(rec), index));
+#endif /* UNIV_ZIP_DEBUG */
+}
+
+/**********************************************************************//**
+Write a BLOB pointer of a record on the leaf page of a clustered index.
+The information must already have been updated on the uncompressed page. */
+void
+page_zip_write_blob_ptr(
+/*====================*/
+	buf_block_t*	block,	/*!< in/out: ROW_FORMAT=COMPRESSED page */
+	const byte*	rec,	/*!< in/out: record whose data is being
+				written */
+	dict_index_t*	index,	/*!< in: index of the page */
+	const rec_offs*	offsets,/*!< in: rec_get_offsets(rec, index) */
+	ulint		n,	/*!< in: column index */
+	mtr_t*		mtr)	/*!< in/out: mini-transaction */
+{
+	const byte*	field;
+	byte*		externs;
+	const page_t* const page = block->page.frame;
+	page_zip_des_t* const page_zip = &block->page.zip;
+	ulint		blob_no;
+	ulint		len;
+
+	ut_ad(page_align(rec) == page);
+	ut_ad(index != NULL);
+	ut_ad(offsets != NULL);
+	ut_ad(page_simple_validate_new((page_t*) page));
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(page_zip_get_size(page_zip)
+	      > PAGE_DATA + page_zip_dir_size(page_zip));
+	ut_ad(rec_offs_comp(offsets));
+	ut_ad(rec_offs_validate(rec, NULL, offsets));
+	ut_ad(rec_offs_any_extern(offsets));
+	ut_ad(rec_offs_nth_extern(offsets, n));
+
+	ut_ad(page_zip->m_start >= PAGE_DATA);
+	ut_ad(page_zip_header_cmp(page_zip, page));
+
+	ut_ad(page_is_leaf(page));
+	ut_ad(dict_index_is_clust(index));
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+
+	blob_no = page_zip_get_n_prev_extern(page_zip, rec, index)
+		+ rec_get_n_extern_new(rec, index, n);
+	ut_a(blob_no < page_zip->n_blobs);
+
+	externs = page_zip->data + page_zip_get_size(page_zip)
+		- (page_dir_get_n_heap(page) - PAGE_HEAP_NO_USER_LOW)
+		* PAGE_ZIP_CLUST_LEAF_SLOT_SIZE;
+
+	field = rec_get_nth_field(rec, offsets, n, &len);
+
+	externs -= (blob_no + 1) * BTR_EXTERN_FIELD_REF_SIZE;
+	field += len - BTR_EXTERN_FIELD_REF_SIZE;
+
+	mtr->zmemcpy<mtr_t::MAYBE_NOP>(*block, externs, field,
+				       BTR_EXTERN_FIELD_REF_SIZE);
+
+#ifdef UNIV_ZIP_DEBUG
+	ut_a(page_zip_validate(page_zip, page, index));
+#endif /* UNIV_ZIP_DEBUG */
+}
+
+/**********************************************************************//**
+Write the node pointer of a record on a non-leaf compressed page. */
+void
+page_zip_write_node_ptr(
+/*====================*/
+	buf_block_t*	block,	/*!< in/out: compressed page */
+	byte*		rec,	/*!< in/out: record */
+	ulint		size,	/*!< in: data size of rec */
+	ulint		ptr,	/*!< in: node pointer */
+	mtr_t*		mtr)	/*!< in/out: mini-transaction */
+{
+	byte*	field;
+	byte*	storage;
+	page_zip_des_t* const page_zip = &block->page.zip;
+
+	ut_d(const page_t* const page = block->page.frame);
+	ut_ad(page_simple_validate_new(page));
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(page_zip_get_size(page_zip)
+	      > PAGE_DATA + page_zip_dir_size(page_zip));
+	ut_ad(page_rec_is_comp(rec));
+
+	ut_ad(page_zip->m_start >= PAGE_DATA);
+	ut_ad(page_zip_header_cmp(page_zip, page));
+
+	ut_ad(!page_is_leaf(page));
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+	MEM_CHECK_DEFINED(rec, size);
+
+	storage = page_zip_dir_start(page_zip)
+		- (rec_get_heap_no_new(rec) - 1) * REC_NODE_PTR_SIZE;
+	field = rec + size - REC_NODE_PTR_SIZE;
+
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+	ut_a(!memcmp(storage, field, REC_NODE_PTR_SIZE));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+	compile_time_assert(REC_NODE_PTR_SIZE == 4);
+	mach_write_to_4(field, ptr);
+	mtr->zmemcpy(*block, storage, field, REC_NODE_PTR_SIZE);
+}
+
+/** Write the DB_TRX_ID,DB_ROLL_PTR into a clustered index leaf page record.
+@param[in,out]	block		ROW_FORMAT=COMPRESSED page
+@param[in,out]	rec		record
+@param[in]	offsets		rec_get_offsets(rec, index)
+@param[in]	trx_id_field	field number of DB_TRX_ID (number of PK fields)
+@param[in]	trx_id		DB_TRX_ID value (transaction identifier)
+@param[in]	roll_ptr	DB_ROLL_PTR value (undo log pointer)
+@param[in,out]	mtr		mini-transaction */
+void
+page_zip_write_trx_id_and_roll_ptr(
+	buf_block_t*	block,
+	byte*		rec,
+	const rec_offs*	offsets,
+	ulint		trx_id_col,
+	trx_id_t	trx_id,
+	roll_ptr_t	roll_ptr,
+	mtr_t*		mtr)
+{
+	page_zip_des_t* const page_zip = &block->page.zip;
+
+	ut_d(const page_t* const page = block->page.frame);
+	ut_ad(page_align(rec) == page);
+	ut_ad(page_simple_validate_new(page));
+	ut_ad(page_zip_simple_validate(page_zip));
+	ut_ad(page_zip_get_size(page_zip)
+	      > PAGE_DATA + page_zip_dir_size(page_zip));
+	ut_ad(rec_offs_validate(rec, NULL, offsets));
+	ut_ad(rec_offs_comp(offsets));
+
+	ut_ad(page_zip->m_start >= PAGE_DATA);
+	ut_ad(page_zip_header_cmp(page_zip, page));
+
+	ut_ad(page_is_leaf(page));
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+
+	constexpr ulint sys_len = DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+	const ulint heap_no = rec_get_heap_no_new(rec);
+	ut_ad(heap_no >= PAGE_HEAP_NO_USER_LOW);
+	byte* storage = page_zip_dir_start(page_zip) - (heap_no - 1) * sys_len;
+
+	compile_time_assert(DATA_TRX_ID + 1 == DATA_ROLL_PTR);
+	ulint len;
+	byte* field = rec_get_nth_field(rec, offsets, trx_id_col, &len);
+	ut_ad(len == DATA_TRX_ID_LEN);
+	ut_ad(field + DATA_TRX_ID_LEN
+	      == rec_get_nth_field(rec, offsets, trx_id_col + 1, &len));
+	ut_ad(len == DATA_ROLL_PTR_LEN);
+	compile_time_assert(DATA_TRX_ID_LEN == 6);
+	mach_write_to_6(field, trx_id);
+	compile_time_assert(DATA_ROLL_PTR_LEN == 7);
+	mach_write_to_7(field + DATA_TRX_ID_LEN, roll_ptr);
+	len = 0;
+	if (heap_no > PAGE_HEAP_NO_USER_LOW) {
+		byte* prev = storage + sys_len;
+		for (; len < sys_len && prev[len] == field[len]; len++);
+		if (len > 4) {
+			/* We save space by replacing a single record
+
+			WRITE,offset(storage),byte[13]
+
+			with up to two records:
+
+			MEMMOVE,offset(storage),len(1 byte),+13(1 byte),
+			WRITE|0x80,0,byte[13-len]
+
+			The single WRITE record would be x+13 bytes long (x>2).
+			The MEMMOVE record would be x+1+1 = x+2 bytes, and
+			the second WRITE would be 1+1+13-len = 15-len bytes.
+
+			The total size is: x+13 versus x+2+15-len = x+17-len.
+			To save space, we must have len>4. */
+			memcpy(storage, prev, len);
+			mtr->memmove(*block, ulint(storage - page_zip->data),
+				     ulint(storage - page_zip->data) + sys_len,
+				     len);
+			storage += len;
+			field += len;
+			if (UNIV_LIKELY(len < sys_len)) {
+				goto write;
+			}
+		} else {
+			len = 0;
+			goto write;
+		}
+	} else {
+write:
+                mtr->zmemcpy<mtr_t::MAYBE_NOP>(*block, storage, field,
+					       sys_len - len);
+	}
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+	ut_a(!memcmp(storage - len, field - len, sys_len));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+}
+
+/**********************************************************************//**
+Clear an area on the uncompressed and compressed page.
+Do not clear the data payload, as that would grow the modification log. */
+static
+void
+page_zip_clear_rec(
+/*===============*/
+	buf_block_t*	block,		/*!< in/out: compressed page */
+	byte*		rec,		/*!< in: record to clear */
+	const dict_index_t*	index,	/*!< in: index of rec */
+	const rec_offs*	offsets,	/*!< in: rec_get_offsets(rec, index) */
+	mtr_t*		mtr)		/*!< in/out: mini-transaction */
+{
+	ulint	heap_no;
+	byte*	storage;
+	byte*	field;
+	ulint	len;
+
+	ut_ad(page_align(rec) == block->page.frame);
+	page_zip_des_t* const page_zip = &block->page.zip;
+
+	/* page_zip_validate() would fail here if a record
+	containing externally stored columns is being deleted. */
+	ut_ad(rec_offs_validate(rec, index, offsets));
+	ut_ad(!page_zip_dir_find(page_zip, page_offset(rec)));
+	ut_ad(page_zip_dir_find_free(page_zip, page_offset(rec)));
+	ut_ad(page_zip_header_cmp(page_zip, block->page.frame));
+
+	heap_no = rec_get_heap_no_new(rec);
+	ut_ad(heap_no >= PAGE_HEAP_NO_USER_LOW);
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+	MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+	MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+			  rec_offs_extra_size(offsets));
+
+	if (!page_is_leaf(block->page.frame)) {
+		/* Clear node_ptr. On the compressed page,
+		there is an array of node_ptr immediately before the
+		dense page directory, at the very end of the page. */
+		storage	= page_zip_dir_start(page_zip);
+		ut_ad(dict_index_get_n_unique_in_tree_nonleaf(index) ==
+		      rec_offs_n_fields(offsets) - 1);
+		field	= rec_get_nth_field(rec, offsets,
+					    rec_offs_n_fields(offsets) - 1,
+					    &len);
+		ut_ad(len == REC_NODE_PTR_SIZE);
+		ut_ad(!rec_offs_any_extern(offsets));
+		memset(field, 0, REC_NODE_PTR_SIZE);
+		storage -= (heap_no - 1) * REC_NODE_PTR_SIZE;
+		len = REC_NODE_PTR_SIZE;
+clear_page_zip:
+		memset(storage, 0, len);
+		mtr->memset(*block, storage - page_zip->data, len, 0);
+	} else if (index->is_clust()) {
+		/* Clear trx_id and roll_ptr. On the compressed page,
+		there is an array of these fields immediately before the
+		dense page directory, at the very end of the page. */
+		const ulint	trx_id_pos
+			= dict_col_get_clust_pos(
+			dict_table_get_sys_col(
+				index->table, DATA_TRX_ID), index);
+		field	= rec_get_nth_field(rec, offsets, trx_id_pos, &len);
+		ut_ad(len == DATA_TRX_ID_LEN);
+		memset(field, 0, DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+		if (rec_offs_any_extern(offsets)) {
+			ulint	i;
+
+			for (i = rec_offs_n_fields(offsets); i--; ) {
+				/* Clear all BLOB pointers in order to make
+				page_zip_validate() pass. */
+				if (rec_offs_nth_extern(offsets, i)) {
+					field = rec_get_nth_field(
+						rec, offsets, i, &len);
+					ut_ad(len
+					      == BTR_EXTERN_FIELD_REF_SIZE);
+					memset(field + len
+					       - BTR_EXTERN_FIELD_REF_SIZE,
+					       0, BTR_EXTERN_FIELD_REF_SIZE);
+				}
+			}
+		}
+
+		len = DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+		storage = page_zip_dir_start(page_zip)
+			- (heap_no - 1)
+			* (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+		goto clear_page_zip;
+	} else {
+		ut_ad(!rec_offs_any_extern(offsets));
+	}
+}
+
+/** Modify the delete-mark flag of a ROW_FORMAT=COMPRESSED record.
+@param[in,out]  block   buffer block
+@param[in,out]  rec     record on a physical index page
+@param[in]      flag    the value of the delete-mark flag
+@param[in,out]  mtr     mini-transaction  */
+void page_zip_rec_set_deleted(buf_block_t *block, rec_t *rec, bool flag,
+                              mtr_t *mtr)
+{
+  ut_ad(page_align(rec) == block->page.frame);
+  byte *slot= page_zip_dir_find(&block->page.zip, page_offset(rec));
+  byte b= *slot;
+  if (flag)
+    b|= (PAGE_ZIP_DIR_SLOT_DEL >> 8);
+  else
+    b&= byte(~(PAGE_ZIP_DIR_SLOT_DEL >> 8));
+  mtr->zmemcpy<mtr_t::MAYBE_NOP>(*block, slot, &b, 1);
+#ifdef UNIV_ZIP_DEBUG
+  ut_a(page_zip_validate(&block->page.zip, block->page.frame, nullptr));
+#endif /* UNIV_ZIP_DEBUG */
+}
+
+/**********************************************************************//**
+Write the "owned" flag of a record on a compressed page.  The n_owned field
+must already have been written on the uncompressed page. */
+void
+page_zip_rec_set_owned(
+/*===================*/
+	buf_block_t*	block,	/*!< in/out: ROW_FORMAT=COMPRESSED page */
+	const byte*	rec,	/*!< in: record on the uncompressed page */
+	ulint		flag,	/*!< in: the owned flag (nonzero=TRUE) */
+	mtr_t*		mtr)	/*!< in/out: mini-transaction */
+{
+  ut_ad(page_align(rec) == block->page.frame);
+  page_zip_des_t *const page_zip= &block->page.zip;
+  byte *slot= page_zip_dir_find(page_zip, page_offset(rec));
+  MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+  byte b= *slot;
+  if (flag)
+    b|= (PAGE_ZIP_DIR_SLOT_OWNED >> 8);
+  else
+    b&= byte(~(PAGE_ZIP_DIR_SLOT_OWNED >> 8));
+  mtr->zmemcpy<mtr_t::MAYBE_NOP>(*block, slot, &b, 1);
+}
+
+/**********************************************************************//**
+Insert a record to the dense page directory. */
+void
+page_zip_dir_insert(
+/*================*/
+	page_cur_t*	cursor,	/*!< in/out: page cursor */
+	uint16_t	free_rec,/*!< in: record from which rec was
+				allocated, or 0 */
+	byte*		rec,	/*!< in: record to insert */
+	mtr_t*		mtr)	/*!< in/out: mini-transaction */
+{
+	ut_ad(page_align(cursor->rec) == cursor->block->page.frame);
+	ut_ad(page_align(rec) == cursor->block->page.frame);
+	page_zip_des_t *const page_zip= &cursor->block->page.zip;
+
+	ulint	n_dense;
+	byte*	slot_rec;
+	byte*	slot_free;
+
+	ut_ad(cursor->rec != rec);
+	ut_ad(page_rec_get_next_const(cursor->rec) == rec);
+	ut_ad(page_zip_simple_validate(page_zip));
+
+	MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+
+	if (page_rec_is_infimum(cursor->rec)) {
+		/* Use the first slot. */
+		slot_rec = page_zip->data + page_zip_get_size(page_zip);
+	} else {
+		byte*	end	= page_zip->data + page_zip_get_size(page_zip);
+		byte*	start	= end - page_zip_dir_user_size(page_zip);
+
+		if (UNIV_LIKELY(!free_rec)) {
+			/* PAGE_N_RECS was already incremented
+			in page_cur_insert_rec_zip(), but the
+			dense directory slot at that position
+			contains garbage.  Skip it. */
+			start += PAGE_ZIP_DIR_SLOT_SIZE;
+		}
+
+		slot_rec = page_zip_dir_find_low(start, end,
+						 page_offset(cursor->rec));
+		ut_a(slot_rec);
+	}
+
+	/* Read the old n_dense (n_heap may have been incremented). */
+	n_dense = page_dir_get_n_heap(page_zip->data)
+		- (PAGE_HEAP_NO_USER_LOW + 1U);
+
+	if (UNIV_UNLIKELY(free_rec)) {
+		/* The record was allocated from the free list.
+		Shift the dense directory only up to that slot.
+		Note that in this case, n_dense is actually
+		off by one, because page_cur_insert_rec_zip()
+		did not increment n_heap. */
+		ut_ad(rec_get_heap_no_new(rec) < n_dense + 1
+		      + PAGE_HEAP_NO_USER_LOW);
+		ut_ad(page_offset(rec) >= free_rec);
+		slot_free = page_zip_dir_find(page_zip, free_rec);
+		ut_ad(slot_free);
+		slot_free += PAGE_ZIP_DIR_SLOT_SIZE;
+	} else {
+		/* The record was allocated from the heap.
+		Shift the entire dense directory. */
+		ut_ad(rec_get_heap_no_new(rec) == n_dense
+		      + PAGE_HEAP_NO_USER_LOW);
+
+		/* Shift to the end of the dense page directory. */
+		slot_free = page_zip->data + page_zip_get_size(page_zip)
+			- PAGE_ZIP_DIR_SLOT_SIZE * n_dense;
+	}
+
+	if (const ulint slot_len = ulint(slot_rec - slot_free)) {
+		/* Shift the dense directory to allocate place for rec. */
+		memmove_aligned<2>(slot_free - PAGE_ZIP_DIR_SLOT_SIZE,
+				   slot_free, slot_len);
+		mtr->memmove(*cursor->block, (slot_free - page_zip->data)
+			     - PAGE_ZIP_DIR_SLOT_SIZE,
+			     slot_free - page_zip->data, slot_len);
+	}
+
+	/* Write the entry for the inserted record.
+	The "owned" flag must be zero. */
+	uint16_t offs = page_offset(rec);
+	if (rec_get_deleted_flag(rec, true)) {
+		offs |= PAGE_ZIP_DIR_SLOT_DEL;
+	}
+
+	mach_write_to_2(slot_rec - PAGE_ZIP_DIR_SLOT_SIZE, offs);
+	mtr->zmemcpy(*cursor->block, slot_rec - page_zip->data
+		     - PAGE_ZIP_DIR_SLOT_SIZE, PAGE_ZIP_DIR_SLOT_SIZE);
+}
+
+/** Shift the dense page directory and the array of BLOB pointers
+when a record is deleted.
+@param[in,out]  block   index page
+@param[in,out]  rec     record being deleted
+@param[in]      index   the index that the page belongs to
+@param[in]      offsets rec_get_offsets(rec, index)
+@param[in]      free    previous start of the free list
+@param[in,out]  mtr     mini-transaction */
+void page_zip_dir_delete(buf_block_t *block, byte *rec,
+                         const dict_index_t *index, const rec_offs *offsets,
+                         const byte *free, mtr_t *mtr)
+{
+  ut_ad(page_align(rec) == block->page.frame);
+  page_zip_des_t *const page_zip= &block->page.zip;
+
+  ut_ad(rec_offs_validate(rec, index, offsets));
+  ut_ad(rec_offs_comp(offsets));
+
+  MEM_CHECK_DEFINED(page_zip->data, page_zip_get_size(page_zip));
+  MEM_CHECK_DEFINED(rec, rec_offs_data_size(offsets));
+  MEM_CHECK_DEFINED(rec - rec_offs_extra_size(offsets),
+		    rec_offs_extra_size(offsets));
+
+  mach_write_to_2(rec - REC_NEXT,
+                  free ? static_cast<uint16_t>(free - rec) : 0);
+  byte *page_free= my_assume_aligned<2>(PAGE_FREE + PAGE_HEADER +
+                                        block->page.frame);
+  mtr->write<2>(*block, page_free, page_offset(rec));
+  byte *garbage= my_assume_aligned<2>(PAGE_GARBAGE + PAGE_HEADER +
+                                      block->page.frame);
+  mtr->write<2>(*block, garbage, rec_offs_size(offsets) +
+                mach_read_from_2(garbage));
+  compile_time_assert(PAGE_GARBAGE == PAGE_FREE + 2);
+  memcpy_aligned<4>(PAGE_FREE + PAGE_HEADER + page_zip->data, page_free, 4);
+  byte *slot_rec= page_zip_dir_find(page_zip, page_offset(rec));
+  ut_a(slot_rec);
+  uint16_t n_recs= page_get_n_recs(block->page.frame);
+  ut_ad(n_recs);
+  ut_ad(n_recs > 1 || page_get_page_no(block->page.frame) == index->page);
+  /* This could not be done before page_zip_dir_find(). */
+  byte *page_n_recs= my_assume_aligned<2>(PAGE_N_RECS + PAGE_HEADER +
+                                          block->page.frame);
+  mtr->write<2>(*block, page_n_recs, n_recs - 1U);
+  memcpy_aligned<2>(PAGE_N_RECS + PAGE_HEADER + page_zip->data, page_n_recs,
+                    2);
+
+  byte *slot_free;
+
+  if (UNIV_UNLIKELY(!free))
+    /* Make the last slot the start of the free list. */
+    slot_free= page_zip->data + page_zip_get_size(page_zip) -
+      PAGE_ZIP_DIR_SLOT_SIZE * (page_dir_get_n_heap(page_zip->data) -
+                                PAGE_HEAP_NO_USER_LOW);
+  else
+  {
+    slot_free= page_zip_dir_find_free(page_zip, page_offset(free));
+    ut_a(slot_free < slot_rec);
+    /* Grow the free list by one slot by moving the start. */
+    slot_free+= PAGE_ZIP_DIR_SLOT_SIZE;
+  }
+
+  const ulint slot_len= slot_rec > slot_free ? ulint(slot_rec - slot_free) : 0;
+  if (slot_len)
+  {
+    memmove_aligned<2>(slot_free + PAGE_ZIP_DIR_SLOT_SIZE, slot_free,
+                       slot_len);
+    mtr->memmove(*block, (slot_free - page_zip->data) + PAGE_ZIP_DIR_SLOT_SIZE,
+                 slot_free - page_zip->data, slot_len);
+  }
+
+  /* Write the entry for the deleted record.
+  The "owned" and "deleted" flags will be cleared. */
+  mach_write_to_2(slot_free, page_offset(rec));
+  mtr->zmemcpy(*block, slot_free - page_zip->data, 2);
+
+  if (const ulint n_ext= rec_offs_n_extern(offsets))
+  {
+    ut_ad(index->is_primary());
+    ut_ad(page_is_leaf(block->page.frame));
+
+    /* Shift and zero fill the array of BLOB pointers. */
+    ulint blob_no = page_zip_get_n_prev_extern(page_zip, rec, index);
+    ut_a(blob_no + n_ext <= page_zip->n_blobs);
+
+    byte *externs= page_zip->data + page_zip_get_size(page_zip) -
+      (page_dir_get_n_heap(block->page.frame) - PAGE_HEAP_NO_USER_LOW) *
+      PAGE_ZIP_CLUST_LEAF_SLOT_SIZE;
+    byte *ext_end= externs - page_zip->n_blobs * FIELD_REF_SIZE;
+
+    /* Shift and zero fill the array. */
+    if (const ulint ext_len= ulint(page_zip->n_blobs - n_ext - blob_no) *
+        BTR_EXTERN_FIELD_REF_SIZE)
+    {
+      memmove(ext_end + n_ext * FIELD_REF_SIZE, ext_end, ext_len);
+      mtr->memmove(*block, (ext_end - page_zip->data) + n_ext * FIELD_REF_SIZE,
+                   ext_end - page_zip->data, ext_len);
+    }
+    memset(ext_end, 0, n_ext * FIELD_REF_SIZE);
+    mtr->memset(*block, ext_end - page_zip->data, n_ext * FIELD_REF_SIZE, 0);
+    page_zip->n_blobs = (page_zip->n_blobs - n_ext) & ((1U << 12) - 1);
+  }
+
+  /* The compression algorithm expects info_bits and n_owned
+  to be 0 for deleted records. */
+  rec[-REC_N_NEW_EXTRA_BYTES]= 0; /* info_bits and n_owned */
+
+  page_zip_clear_rec(block, rec, index, offsets, mtr);
+}
+
+/**********************************************************************//**
+Reorganize and compress a page.  This is a low-level operation for
+compressed pages, to be used when page_zip_compress() fails.
+On success, redo log will be written.
+The function btr_page_reorganize() should be preferred whenever possible.
+IMPORTANT: if page_zip_reorganize() is invoked on a leaf page of a
+non-clustered index, the caller must update the insert buffer free
+bits in the same mini-transaction in such a way that the modification
+will be redo-logged.
+@return error code
+@retval DB_FAIL on overflow; the block_zip will be left intact */
+dberr_t
+page_zip_reorganize(
+	buf_block_t*	block,	/*!< in/out: page with compressed page;
+				on the compressed page, in: size;
+				out: data, n_blobs,
+				m_start, m_end, m_nonempty */
+	dict_index_t*	index,	/*!< in: index of the B-tree node */
+	ulint		z_level,/*!< in: compression level */
+	mtr_t*		mtr,	/*!< in: mini-transaction */
+	bool		restore)/*!< whether to restore on failure */
+{
+	page_t*		page		= buf_block_get_frame(block);
+	buf_block_t*	temp_block;
+	page_t*		temp_page;
+
+	ut_ad(mtr->memo_contains_flagged(block, MTR_MEMO_PAGE_X_FIX));
+	ut_ad(block->page.zip.data);
+	ut_ad(page_is_comp(page));
+	ut_ad(!dict_index_is_ibuf(index));
+	ut_ad(!index->table->is_temporary());
+	/* Note that page_zip_validate(page_zip, page, index) may fail here. */
+	MEM_CHECK_DEFINED(page, srv_page_size);
+	MEM_CHECK_DEFINED(buf_block_get_page_zip(block)->data,
+			  page_zip_get_size(buf_block_get_page_zip(block)));
+
+	/* Disable logging */
+	mtr_log_t	log_mode = mtr_set_log_mode(mtr, MTR_LOG_NONE);
+
+	temp_block = buf_block_alloc();
+	btr_search_drop_page_hash_index(block, false);
+	temp_page = temp_block->page.frame;
+
+	/* Copy the old page to temporary space */
+	memcpy_aligned<UNIV_PAGE_SIZE_MIN>(temp_page, block->page.frame,
+					   srv_page_size);
+
+	/* Recreate the page: note that global data on page (possible
+	segment headers, next page-field, etc.) is preserved intact */
+
+	page_create(block, mtr, true);
+	if (index->is_spatial()) {
+		mach_write_to_2(FIL_PAGE_TYPE + page, FIL_PAGE_RTREE);
+		memcpy_aligned<2>(block->page.zip.data + FIL_PAGE_TYPE,
+				  page + FIL_PAGE_TYPE, 2);
+		memset(FIL_RTREE_SPLIT_SEQ_NUM + page, 0, 8);
+		memset(FIL_RTREE_SPLIT_SEQ_NUM + block->page.zip.data, 0, 8);
+	}
+
+	/* Copy the records from the temporary space to the recreated page;
+	do not copy the lock bits yet */
+
+	dberr_t err = page_copy_rec_list_end_no_locks(
+		block, temp_block, page_get_infimum_rec(temp_page),
+		index, mtr);
+
+	/* Copy the PAGE_MAX_TRX_ID or PAGE_ROOT_AUTO_INC. */
+	memcpy_aligned<8>(page + (PAGE_HEADER + PAGE_MAX_TRX_ID),
+			  temp_page + (PAGE_HEADER + PAGE_MAX_TRX_ID), 8);
+	/* PAGE_MAX_TRX_ID must be set on secondary index leaf pages. */
+	ut_ad(err != DB_SUCCESS
+	      || index->is_clust() || !page_is_leaf(temp_page)
+	      || page_get_max_trx_id(page) != 0);
+	/* PAGE_MAX_TRX_ID must be zero on non-leaf pages other than
+	clustered index root pages. */
+	ut_ad(err != DB_SUCCESS
+	      || page_get_max_trx_id(page) == 0
+	      || (index->is_clust()
+		  ? !page_has_siblings(temp_page)
+		  : page_is_leaf(temp_page)));
+
+	/* Restore logging. */
+	mtr_set_log_mode(mtr, log_mode);
+
+	if (!page_zip_compress(block, index, z_level, mtr)) {
+		if (restore) {
+			/* Restore the old page and exit. */
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+			/* Check that the bytes that we skip are identical. */
+			ut_a(!memcmp(page, temp_page, PAGE_HEADER));
+			ut_a(!memcmp(PAGE_HEADER + PAGE_N_RECS + page,
+				     PAGE_HEADER + PAGE_N_RECS + temp_page,
+				     PAGE_DATA - (PAGE_HEADER + PAGE_N_RECS)));
+			ut_a(!memcmp(srv_page_size - FIL_PAGE_DATA_END + page,
+				     srv_page_size - FIL_PAGE_DATA_END
+				     + temp_page,
+				     FIL_PAGE_DATA_END));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+
+			memcpy(PAGE_HEADER + page, PAGE_HEADER + temp_page,
+			       PAGE_N_RECS - PAGE_N_DIR_SLOTS);
+			memcpy(PAGE_DATA + page, PAGE_DATA + temp_page,
+			       srv_page_size - PAGE_DATA - FIL_PAGE_DATA_END);
+
+#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
+			ut_a(!memcmp(page, temp_page, srv_page_size));
+#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
+		}
+
+		err = DB_FAIL;
+	} else {
+		lock_move_reorganize_page(block, temp_block);
+	}
+
+	buf_block_free(temp_block);
+	return err;
+}
+
+/**********************************************************************//**
+Copy the records of a page byte for byte.  Do not copy the page header
+or trailer, except those B-tree header fields that are directly
+related to the storage of records.  Also copy PAGE_MAX_TRX_ID.
+NOTE: The caller must update the lock table and the adaptive hash index. */
+void
+page_zip_copy_recs(
+	buf_block_t*		block,		/*!< in/out: buffer block */
+	const page_zip_des_t*	src_zip,	/*!< in: compressed page */
+	const page_t*		src,		/*!< in: page */
+	dict_index_t*		index,		/*!< in: index of the B-tree */
+	mtr_t*			mtr)		/*!< in: mini-transaction */
+{
+	page_t* page = block->page.frame;
+	page_zip_des_t* page_zip = &block->page.zip;
+
+	ut_ad(mtr->memo_contains_flagged(block, MTR_MEMO_PAGE_X_FIX));
+	ut_ad(mtr->memo_contains_page_flagged(src, MTR_MEMO_PAGE_X_FIX));
+	ut_ad(!dict_index_is_ibuf(index));
+	ut_ad(!index->table->is_temporary());
+#ifdef UNIV_ZIP_DEBUG
+	/* The B-tree operations that call this function may set
+	FIL_PAGE_PREV or PAGE_LEVEL, causing a temporary min_rec_flag
+	mismatch.  A strict page_zip_validate() will be executed later
+	during the B-tree operations. */
+	ut_a(page_zip_validate_low(src_zip, src, index, TRUE));
+#endif /* UNIV_ZIP_DEBUG */
+	ut_a(page_zip_get_size(page_zip) == page_zip_get_size(src_zip));
+	if (UNIV_UNLIKELY(src_zip->n_blobs)) {
+		ut_a(page_is_leaf(src));
+		ut_a(dict_index_is_clust(index));
+	}
+
+	MEM_CHECK_ADDRESSABLE(page, srv_page_size);
+	MEM_CHECK_ADDRESSABLE(page_zip->data, page_zip_get_size(page_zip));
+	MEM_CHECK_DEFINED(src, srv_page_size);
+	MEM_CHECK_DEFINED(src_zip->data, page_zip_get_size(page_zip));
+
+	/* Copy those B-tree page header fields that are related to
+	the records stored in the page.  Also copy the field
+	PAGE_MAX_TRX_ID.  Skip the rest of the page header and
+	trailer.  On the compressed page, there is no trailer. */
+	compile_time_assert(PAGE_MAX_TRX_ID + 8 == PAGE_HEADER_PRIV_END);
+	memcpy_aligned<2>(PAGE_HEADER + page, PAGE_HEADER + src,
+			  PAGE_HEADER_PRIV_END);
+	memcpy_aligned<2>(PAGE_DATA + page, PAGE_DATA + src,
+			  srv_page_size - (PAGE_DATA + FIL_PAGE_DATA_END));
+	memcpy_aligned<2>(PAGE_HEADER + page_zip->data,
+			  PAGE_HEADER + src_zip->data,
+			  PAGE_HEADER_PRIV_END);
+	memcpy_aligned<2>(PAGE_DATA + page_zip->data,
+			  PAGE_DATA + src_zip->data,
+			  page_zip_get_size(page_zip) - PAGE_DATA);
+
+	if (dict_index_is_clust(index)) {
+		/* Reset the PAGE_ROOT_AUTO_INC field when copying
+		from a root page. */
+		memset_aligned<8>(PAGE_HEADER + PAGE_ROOT_AUTO_INC
+				  + page, 0, 8);
+		memset_aligned<8>(PAGE_HEADER + PAGE_ROOT_AUTO_INC
+				  + page_zip->data, 0, 8);
+	} else {
+		/* The PAGE_MAX_TRX_ID must be nonzero on leaf pages
+		of secondary indexes, and 0 on others. */
+		ut_ad(!page_is_leaf(src) == !page_get_max_trx_id(src));
+	}
+
+	/* Copy all fields of src_zip to page_zip, except the pointer
+	to the compressed data page. */
+	{
+		page_zip_t*	data = page_zip->data;
+		new (page_zip) page_zip_des_t(*src_zip, false);
+		page_zip->data = data;
+	}
+	ut_ad(page_zip_get_trailer_len(page_zip, dict_index_is_clust(index))
+	      + page_zip->m_end < page_zip_get_size(page_zip));
+
+	if (!page_is_leaf(src)
+	    && UNIV_UNLIKELY(!page_has_prev(src))
+	    && UNIV_LIKELY(page_has_prev(page))) {
+		/* Clear the REC_INFO_MIN_REC_FLAG of the first user record. */
+		ulint	offs = rec_get_next_offs(page + PAGE_NEW_INFIMUM,
+						 TRUE);
+		if (UNIV_LIKELY(offs != PAGE_NEW_SUPREMUM)) {
+			rec_t*	rec = page + offs;
+			ut_a(rec[-REC_N_NEW_EXTRA_BYTES]
+			     & REC_INFO_MIN_REC_FLAG);
+			rec[-REC_N_NEW_EXTRA_BYTES]
+				&= byte(~REC_INFO_MIN_REC_FLAG);
+		}
+	}
+
+#ifdef UNIV_ZIP_DEBUG
+	ut_a(page_zip_validate(page_zip, page, index));
+#endif /* UNIV_ZIP_DEBUG */
+	page_zip_compress_write_log(block, index, mtr);
+}
+#endif /* !UNIV_INNOCHECKSUM */
+
+/** Calculate the compressed page checksum.
+@param data		compressed page
+@param size		size of compressed page
+@param use_adler	whether to use Adler32 instead of a XOR of 3 CRC-32C
+@return page checksum */
+uint32_t page_zip_calc_checksum(const void *data, size_t size, bool use_adler)
+{
+	uLong		adler;
+	const Bytef*	s = static_cast<const byte*>(data);
+
+	/* Exclude FIL_PAGE_SPACE_OR_CHKSUM, FIL_PAGE_LSN,
+	and FIL_PAGE_FILE_FLUSH_LSN from the checksum. */
+	ut_ad(size > FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
+
+	if (!use_adler) {
+		return my_crc32c(0, s + FIL_PAGE_OFFSET,
+				 FIL_PAGE_LSN - FIL_PAGE_OFFSET)
+			^ my_crc32c(0, s + FIL_PAGE_TYPE, 2)
+			^ my_crc32c(0, s + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID,
+				    size - FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
+	} else {
+		adler = adler32(0L, s + FIL_PAGE_OFFSET,
+				FIL_PAGE_LSN - FIL_PAGE_OFFSET);
+		adler = adler32(adler, s + FIL_PAGE_TYPE, 2);
+		adler = adler32(
+			adler, s + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID,
+			static_cast<uInt>(size)
+			- FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
+
+		return(uint32_t(adler));
+	}
+}
+
+/** Validate the checksum on a ROW_FORMAT=COMPRESSED page.
+@param data    ROW_FORMAT=COMPRESSED page
+@param size    size of the page, in bytes
+@return whether the stored checksum matches innodb_checksum_algorithm */
+bool page_zip_verify_checksum(const byte *data, size_t size)
+{
+	if (buf_is_zeroes(span<const byte>(data, size))) {
+		return true;
+	}
+
+	const uint32_t stored = mach_read_from_4(
+		data + FIL_PAGE_SPACE_OR_CHKSUM);
+
+	uint32_t calc = page_zip_calc_checksum(data, size, false);
+
+#ifdef UNIV_INNOCHECKSUM
+	extern FILE* log_file;
+	extern uint32_t cur_page_num;
+
+	if (log_file) {
+		fprintf(log_file, "page::" UINT32PF ";"
+			" checksum: calculated = " UINT32PF ";"
+			" recorded = " UINT32PF "\n", cur_page_num,
+			calc, stored);
+	}
+#endif /* UNIV_INNOCHECKSUM */
+
+	if (stored == calc) {
+		return(TRUE);
+	}
+
+#ifndef UNIV_INNOCHECKSUM
+	switch (srv_checksum_algorithm) {
+	case SRV_CHECKSUM_ALGORITHM_STRICT_FULL_CRC32:
+	case SRV_CHECKSUM_ALGORITHM_STRICT_CRC32:
+		break;
+	default:
+		if (stored == BUF_NO_CHECKSUM_MAGIC) {
+			return(TRUE);
+		}
+
+		return stored == page_zip_calc_checksum(data, size, true);
+	}
+#endif /* !UNIV_INNOCHECKSUM */
+
+	return FALSE;
+}