~drizzle-trunk/drizzle/development

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

Copyright (C) 1996, 2009, Innobase Oy. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free Software

Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with

this program; if not, write to the Free Software Foundation, Inc., 51 Franklin

St, Fifth Floor, Boston, MA 02110-1301 USA

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

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

@file trx/trx0undo.c

Transaction undo log

Created 3/26/1996 Heikki Tuuri

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

#include "trx0undo.h"

#ifdef UNIV_NONINL

#include "trx0undo.ic"

#endif

#include "fsp0fsp.h"

#ifndef UNIV_HOTBACKUP

#include "mach0data.h"

#include "mtr0log.h"

#include "trx0rseg.h"

#include "trx0trx.h"

#include "srv0srv.h"

#include "trx0rec.h"

#include "trx0purge.h"

/* How should the old versions in the history list be managed?

   ----------------------------------------------------------

If each transaction is given a whole page for its update undo log, file

space consumption can be 10 times higher than necessary. Therefore,

partly filled update undo log pages should be reusable. But then there

is no way individual pages can be ordered so that the ordering agrees

with the serialization numbers of the transactions on the pages. Thus,

the history list must be formed of undo logs, not their header pages as

it was in the old implementation.

	However, on a single header page the transactions are placed in

the order of their serialization numbers. As old versions are purged, we

may free the page when the last transaction on the page has been purged.

	A problem is that the purge has to go through the transactions

in the serialization order. This means that we have to look through all

rollback segments for the one that has the smallest transaction number

in its history list.

	When should we do a purge? A purge is necessary when space is

running out in any of the rollback segments. Then we may have to purge

also old version which might be needed by some consistent read. How do

we trigger the start of a purge? When a transaction writes to an undo log,

it may notice that the space is running out. When a read view is closed,

it may make some history superfluous. The server can have an utility which

periodically checks if it can purge some history.

	In a parallellized purge we have the problem that a query thread

can remove a delete marked clustered index record before another query

thread has processed an earlier version of the record, which cannot then

be done because the row cannot be constructed from the clustered index

record. To avoid this problem, we will store in the update and delete mark

undo record also the columns necessary to construct the secondary index

entries which are modified.

	We can latch the stack of versions of a single clustered index record

by taking a latch on the clustered index page. As long as the latch is held,

no new versions can be added and no versions removed by undo. But, a purge

can still remove old versions from the bottom of the stack. */

/* How to protect rollback segments, undo logs, and history lists with

   -------------------------------------------------------------------

latches?

-------

The contention of the kernel mutex should be minimized. When a transaction

does its first insert or modify in an index, an undo log is assigned for it.

Then we must have an x-latch to the rollback segment header.

	When the transaction does more modifys or rolls back, the undo log is

protected with undo_mutex in the transaction.

	When the transaction commits, its insert undo log is either reset and

cached for a fast reuse, or freed. In these cases we must have an x-latch on

the rollback segment page. The update undo log is put to the history list. If

it is not suitable for reuse, its slot in the rollback segment is reset. In

both cases, an x-latch must be acquired on the rollback segment.

	The purge operation steps through the history list without modifying

it until a truncate operation occurs, which can remove undo logs from the end

of the list and release undo log segments. In stepping through the list,

s-latches on the undo log pages are enough, but in a truncate, x-latches must

be obtained on the rollback segment and individual pages. */

#endif /* !UNIV_HOTBACKUP */

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

Initializes the fields in an undo log segment page. */

static

void

trx_undo_page_init(

/*===============*/

	page_t* undo_page,	/*!< in: undo log segment page */

	ulint	type,		/*!< in: undo log segment type */

	mtr_t*	mtr);		/*!< in: mtr */

#ifndef UNIV_HOTBACKUP

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

Creates and initializes an undo log memory object.

@return	own: the undo log memory object */

static

trx_undo_t*

trx_undo_mem_create(

/*================*/

	trx_rseg_t*	rseg,	/*!< in: rollback segment memory object */

	ulint		id,	/*!< in: slot index within rseg */

	ulint		type,	/*!< in: type of the log: TRX_UNDO_INSERT or

				TRX_UNDO_UPDATE */

	trx_id_t	trx_id,	/*!< in: id of the trx for which the undo log

				is created */

	const XID*	xid,	/*!< in: X/Open XA transaction identification*/

	ulint		page_no,/*!< in: undo log header page number */

	ulint		offset);/*!< in: undo log header byte offset on page */

#endif /* !UNIV_HOTBACKUP */

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

Initializes a cached insert undo log header page for new use. NOTE that this

function has its own log record type MLOG_UNDO_HDR_REUSE. You must NOT change

the operation of this function!

@return	undo log header byte offset on page */

static

ulint

trx_undo_insert_header_reuse(

/*=========================*/

	page_t*		undo_page,	/*!< in/out: insert undo log segment

					header page, x-latched */

	trx_id_t	trx_id,		/*!< in: transaction id */

	mtr_t*		mtr);		/*!< in: mtr */

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

If an update undo log can be discarded immediately, this function frees the

space, resetting the page to the proper state for caching. */

static

void

trx_undo_discard_latest_update_undo(

/*================================*/

	page_t*	undo_page,	/*!< in: header page of an undo log of size 1 */

	mtr_t*	mtr);		/*!< in: mtr */

#ifndef UNIV_HOTBACKUP

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

Gets the previous record in an undo log from the previous page.

@return	undo log record, the page s-latched, NULL if none */

static

trx_undo_rec_t*

trx_undo_get_prev_rec_from_prev_page(

/*=================================*/

	trx_undo_rec_t*	rec,	/*!< in: undo record */

	ulint		page_no,/*!< in: undo log header page number */

	ulint		offset,	/*!< in: undo log header offset on page */

	mtr_t*		mtr)	/*!< in: mtr */

{

	ulint	space;

	ulint	zip_size;

	ulint	prev_page_no;

	page_t* prev_page;

	page_t*	undo_page;

	undo_page = page_align(rec);

	prev_page_no = flst_get_prev_addr(undo_page + TRX_UNDO_PAGE_HDR

					  + TRX_UNDO_PAGE_NODE, mtr)

		.page;

	if (prev_page_no == FIL_NULL) {

		return(NULL);

	}

	space = page_get_space_id(undo_page);

	zip_size = fil_space_get_zip_size(space);

	prev_page = trx_undo_page_get_s_latched(space, zip_size,

						prev_page_no, mtr);

	return(trx_undo_page_get_last_rec(prev_page, page_no, offset));

}

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

Gets the previous record in an undo log.

@return	undo log record, the page s-latched, NULL if none */

UNIV_INTERN

trx_undo_rec_t*

trx_undo_get_prev_rec(

/*==================*/

	trx_undo_rec_t*	rec,	/*!< in: undo record */

	ulint		page_no,/*!< in: undo log header page number */

	ulint		offset,	/*!< in: undo log header offset on page */

	mtr_t*		mtr)	/*!< in: mtr */

{

	trx_undo_rec_t*	prev_rec;

	prev_rec = trx_undo_page_get_prev_rec(rec, page_no, offset);

	if (prev_rec) {

		return(prev_rec);

	}

	/* We have to go to the previous undo log page to look for the

	previous record */

	return(trx_undo_get_prev_rec_from_prev_page(rec, page_no, offset,

						    mtr));

}

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

Gets the next record in an undo log from the next page.

@return	undo log record, the page latched, NULL if none */

static

trx_undo_rec_t*

trx_undo_get_next_rec_from_next_page(

/*=================================*/

	ulint	space,	/*!< in: undo log header space */

	ulint	zip_size,/*!< in: compressed page size in bytes

			or 0 for uncompressed pages */

	page_t*	undo_page, /*!< in: undo log page */

	ulint	page_no,/*!< in: undo log header page number */

	ulint	offset,	/*!< in: undo log header offset on page */

	ulint	mode,	/*!< in: latch mode: RW_S_LATCH or RW_X_LATCH */

	mtr_t*	mtr)	/*!< in: mtr */

{

	trx_ulogf_t*	log_hdr;

	ulint		next_page_no;

	page_t*		next_page;

	ulint		next;

	if (page_no == page_get_page_no(undo_page)) {

		log_hdr = undo_page + offset;

		next = mach_read_from_2(log_hdr + TRX_UNDO_NEXT_LOG);

		if (next != 0) {

			return(NULL);

		}

	}

	next_page_no = flst_get_next_addr(undo_page + TRX_UNDO_PAGE_HDR

					  + TRX_UNDO_PAGE_NODE, mtr)

		.page;

	if (next_page_no == FIL_NULL) {

		return(NULL);

	}

	if (mode == RW_S_LATCH) {

		next_page = trx_undo_page_get_s_latched(space, zip_size,

							next_page_no, mtr);

	} else {

		ut_ad(mode == RW_X_LATCH);

		next_page = trx_undo_page_get(space, zip_size,

					      next_page_no, mtr);

	}

	return(trx_undo_page_get_first_rec(next_page, page_no, offset));

}

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

Gets the next record in an undo log.

@return	undo log record, the page s-latched, NULL if none */

UNIV_INTERN

trx_undo_rec_t*

trx_undo_get_next_rec(

/*==================*/

	trx_undo_rec_t*	rec,	/*!< in: undo record */

	ulint		page_no,/*!< in: undo log header page number */

	ulint		offset,	/*!< in: undo log header offset on page */

	mtr_t*		mtr)	/*!< in: mtr */

{

	ulint		space;

	ulint		zip_size;

	trx_undo_rec_t*	next_rec;

	next_rec = trx_undo_page_get_next_rec(rec, page_no, offset);

	if (next_rec) {

		return(next_rec);

	}

	space = page_get_space_id(page_align(rec));

	zip_size = fil_space_get_zip_size(space);

	return(trx_undo_get_next_rec_from_next_page(space, zip_size,

						    page_align(rec),

						    page_no, offset,

						    RW_S_LATCH, mtr));

}

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

Gets the first record in an undo log.

@return	undo log record, the page latched, NULL if none */

UNIV_INTERN

trx_undo_rec_t*

trx_undo_get_first_rec(

/*===================*/

	ulint	space,	/*!< in: undo log header space */

	ulint	zip_size,/*!< in: compressed page size in bytes

			or 0 for uncompressed pages */

	ulint	page_no,/*!< in: undo log header page number */

	ulint	offset,	/*!< in: undo log header offset on page */

	ulint	mode,	/*!< in: latching mode: RW_S_LATCH or RW_X_LATCH */

	mtr_t*	mtr)	/*!< in: mtr */

{

	page_t*		undo_page;

	trx_undo_rec_t*	rec;

	if (mode == RW_S_LATCH) {

		undo_page = trx_undo_page_get_s_latched(space, zip_size,

							page_no, mtr);

	} else {

		undo_page = trx_undo_page_get(space, zip_size, page_no, mtr);

	}

	rec = trx_undo_page_get_first_rec(undo_page, page_no, offset);

	if (rec) {

		return(rec);

	}

	return(trx_undo_get_next_rec_from_next_page(space, zip_size,

						    undo_page, page_no, offset,

						    mode, mtr));

}

/*============== UNDO LOG FILE COPY CREATION AND FREEING ==================*/

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

Writes the mtr log entry of an undo log page initialization. */

UNIV_INLINE

void

trx_undo_page_init_log(

/*===================*/

	page_t* undo_page,	/*!< in: undo log page */

	ulint	type,		/*!< in: undo log type */

	mtr_t*	mtr)		/*!< in: mtr */

{

	mlog_write_initial_log_record(undo_page, MLOG_UNDO_INIT, mtr);

	mlog_catenate_ulint_compressed(mtr, type);

}

#else /* !UNIV_HOTBACKUP */

# define trx_undo_page_init_log(undo_page,type,mtr) ((void) 0)

#endif /* !UNIV_HOTBACKUP */

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

Parses the redo log entry of an undo log page initialization.

@return	end of log record or NULL */

UNIV_INTERN

byte*

trx_undo_parse_page_init(

/*=====================*/

	byte*	ptr,	/*!< in: buffer */

	byte*	end_ptr,/*!< in: buffer end */

	page_t*	page,	/*!< in: page or NULL */

	mtr_t*	mtr)	/*!< in: mtr or NULL */

{

	ulint	type;

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

	if (ptr == NULL) {

		return(NULL);

	}

	if (page) {

		trx_undo_page_init(page, type, mtr);

	}

	return(ptr);

}

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

Initializes the fields in an undo log segment page. */

static

void

trx_undo_page_init(

/*===============*/

	page_t* undo_page,	/*!< in: undo log segment page */

	ulint	type,		/*!< in: undo log segment type */

	mtr_t*	mtr)		/*!< in: mtr */

{

	trx_upagef_t*	page_hdr;

	page_hdr = undo_page + TRX_UNDO_PAGE_HDR;

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_TYPE, type);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_START,

			TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_HDR_SIZE);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_FREE,

			TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_HDR_SIZE);

	fil_page_set_type(undo_page, FIL_PAGE_UNDO_LOG);

	trx_undo_page_init_log(undo_page, type, mtr);

}

#ifndef UNIV_HOTBACKUP

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

Creates a new undo log segment in file.

@return DB_SUCCESS if page creation OK possible error codes are:

DB_TOO_MANY_CONCURRENT_TRXS DB_OUT_OF_FILE_SPACE */

static

ulint

trx_undo_seg_create(

/*================*/

	trx_rseg_t*	rseg __attribute__((unused)),/*!< in: rollback segment */

	trx_rsegf_t*	rseg_hdr,/*!< in: rollback segment header, page

				x-latched */

	ulint		type,	/*!< in: type of the segment: TRX_UNDO_INSERT or

				TRX_UNDO_UPDATE */

	ulint*		id,	/*!< out: slot index within rseg header */

	page_t**	undo_page,

				/*!< out: segment header page x-latched, NULL

				if there was an error */

	mtr_t*		mtr)	/*!< in: mtr */

{

	ulint		slot_no;

	ulint		space;

	buf_block_t*	block;

	trx_upagef_t*	page_hdr;

	trx_usegf_t*	seg_hdr;

	ulint		n_reserved;

	ibool		success;

	ulint		err = DB_SUCCESS;

	ut_ad(mtr && id && rseg_hdr);

	ut_ad(mutex_own(&(rseg->mutex)));

	/*	fputs(type == TRX_UNDO_INSERT

	? "Creating insert undo log segment\n"

	: "Creating update undo log segment\n", stderr); */

	slot_no = trx_rsegf_undo_find_free(rseg_hdr, mtr);

	if (slot_no == ULINT_UNDEFINED) {

		ut_print_timestamp(stderr);

		fprintf(stderr,

			"  InnoDB: Warning: cannot find a free slot for"

			" an undo log. Do you have too\n"

			"InnoDB: many active transactions"

			" running concurrently?\n");

		return(DB_TOO_MANY_CONCURRENT_TRXS);

	}

	space = page_get_space_id(page_align(rseg_hdr));

	success = fsp_reserve_free_extents(&n_reserved, space, 2, FSP_UNDO,

					   mtr);

	if (!success) {

		return(DB_OUT_OF_FILE_SPACE);

	}

	/* Allocate a new file segment for the undo log */

	block = fseg_create_general(space, 0,

				    TRX_UNDO_SEG_HDR

				    + TRX_UNDO_FSEG_HEADER, TRUE, mtr);

	fil_space_release_free_extents(space, n_reserved);

	if (block == NULL) {

		/* No space left */

		return(DB_OUT_OF_FILE_SPACE);

	}

	buf_block_dbg_add_level(block, SYNC_TRX_UNDO_PAGE);

	*undo_page = buf_block_get_frame(block);

	page_hdr = *undo_page + TRX_UNDO_PAGE_HDR;

	seg_hdr = *undo_page + TRX_UNDO_SEG_HDR;

	trx_undo_page_init(*undo_page, type, mtr);

	mlog_write_ulint(page_hdr + TRX_UNDO_PAGE_FREE,

			 TRX_UNDO_SEG_HDR + TRX_UNDO_SEG_HDR_SIZE,

			 MLOG_2BYTES, mtr);

	mlog_write_ulint(seg_hdr + TRX_UNDO_LAST_LOG, 0, MLOG_2BYTES, mtr);

	flst_init(seg_hdr + TRX_UNDO_PAGE_LIST, mtr);

	flst_add_last(seg_hdr + TRX_UNDO_PAGE_LIST,

		      page_hdr + TRX_UNDO_PAGE_NODE, mtr);

	trx_rsegf_set_nth_undo(rseg_hdr, slot_no,

			       page_get_page_no(*undo_page), mtr);

	*id = slot_no;

	return(err);

}

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

Writes the mtr log entry of an undo log header initialization. */

UNIV_INLINE

void

trx_undo_header_create_log(

/*=======================*/

	const page_t*	undo_page,	/*!< in: undo log header page */

	trx_id_t	trx_id,		/*!< in: transaction id */

	mtr_t*		mtr)		/*!< in: mtr */

{

	mlog_write_initial_log_record(undo_page, MLOG_UNDO_HDR_CREATE, mtr);

	mlog_catenate_ull_compressed(mtr, trx_id);

}

#else /* !UNIV_HOTBACKUP */

# define trx_undo_header_create_log(undo_page,trx_id,mtr) ((void) 0)

#endif /* !UNIV_HOTBACKUP */

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

Creates a new undo log header in file. NOTE that this function has its own

log record type MLOG_UNDO_HDR_CREATE. You must NOT change the operation of

this function!

@return	header byte offset on page */

static

ulint

trx_undo_header_create(

/*===================*/

	page_t*		undo_page,	/*!< in/out: undo log segment

					header page, x-latched; it is

					assumed that there is

					TRX_UNDO_LOG_XA_HDR_SIZE bytes

					free space on it */

	trx_id_t	trx_id,		/*!< in: transaction id */

	mtr_t*		mtr)		/*!< in: mtr */

{

	trx_upagef_t*	page_hdr;

	trx_usegf_t*	seg_hdr;

	trx_ulogf_t*	log_hdr;

	trx_ulogf_t*	prev_log_hdr;

	ulint		prev_log;

	ulint		free;

	ulint		new_free;

	ut_ad(mtr && undo_page);

	page_hdr = undo_page + TRX_UNDO_PAGE_HDR;

	seg_hdr = undo_page + TRX_UNDO_SEG_HDR;

	free = mach_read_from_2(page_hdr + TRX_UNDO_PAGE_FREE);

	log_hdr = undo_page + free;

	new_free = free + TRX_UNDO_LOG_OLD_HDR_SIZE;

	ut_a(free + TRX_UNDO_LOG_XA_HDR_SIZE < UNIV_PAGE_SIZE - 100);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_START, new_free);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_FREE, new_free);

	mach_write_to_2(seg_hdr + TRX_UNDO_STATE, TRX_UNDO_ACTIVE);

	prev_log = mach_read_from_2(seg_hdr + TRX_UNDO_LAST_LOG);

	if (prev_log != 0) {

		prev_log_hdr = undo_page + prev_log;

		mach_write_to_2(prev_log_hdr + TRX_UNDO_NEXT_LOG, free);

	}

	mach_write_to_2(seg_hdr + TRX_UNDO_LAST_LOG, free);

	log_hdr = undo_page + free;

	mach_write_to_2(log_hdr + TRX_UNDO_DEL_MARKS, TRUE);

	mach_write_to_8(log_hdr + TRX_UNDO_TRX_ID, trx_id);

	mach_write_to_2(log_hdr + TRX_UNDO_LOG_START, new_free);

	mach_write_to_1(log_hdr + TRX_UNDO_XID_EXISTS, FALSE);

	mach_write_to_1(log_hdr + TRX_UNDO_DICT_TRANS, FALSE);

	mach_write_to_2(log_hdr + TRX_UNDO_NEXT_LOG, 0);

	mach_write_to_2(log_hdr + TRX_UNDO_PREV_LOG, prev_log);

	/* Write the log record about the header creation */

	trx_undo_header_create_log(undo_page, trx_id, mtr);

	return(free);

}

#ifndef UNIV_HOTBACKUP

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

Write X/Open XA Transaction Identification (XID) to undo log header */

static

void

trx_undo_write_xid(

/*===============*/

	trx_ulogf_t*	log_hdr,/*!< in: undo log header */

	const XID*	xid,	/*!< in: X/Open XA Transaction Identification */

	mtr_t*		mtr)	/*!< in: mtr */

{

	mlog_write_ulint(log_hdr + TRX_UNDO_XA_FORMAT,

			 (ulint)xid->formatID, MLOG_4BYTES, mtr);

	mlog_write_ulint(log_hdr + TRX_UNDO_XA_TRID_LEN,

			 (ulint)xid->gtrid_length, MLOG_4BYTES, mtr);

	mlog_write_ulint(log_hdr + TRX_UNDO_XA_BQUAL_LEN,

			 (ulint)xid->bqual_length, MLOG_4BYTES, mtr);

	mlog_write_string(log_hdr + TRX_UNDO_XA_XID, (const byte*) xid->data,

			  XIDDATASIZE, mtr);

}

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

Read X/Open XA Transaction Identification (XID) from undo log header */

static

void

trx_undo_read_xid(

/*==============*/

	trx_ulogf_t*	log_hdr,/*!< in: undo log header */

	XID*		xid)	/*!< out: X/Open XA Transaction Identification */

{

	xid->formatID = (long)mach_read_from_4(log_hdr + TRX_UNDO_XA_FORMAT);

	xid->gtrid_length

		= (long) mach_read_from_4(log_hdr + TRX_UNDO_XA_TRID_LEN);

	xid->bqual_length

		= (long) mach_read_from_4(log_hdr + TRX_UNDO_XA_BQUAL_LEN);

	memcpy(xid->data, log_hdr + TRX_UNDO_XA_XID, XIDDATASIZE);

}

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

Adds space for the XA XID after an undo log old-style header. */

static

void

trx_undo_header_add_space_for_xid(

/*==============================*/

	page_t*		undo_page,/*!< in: undo log segment header page */

	trx_ulogf_t*	log_hdr,/*!< in: undo log header */

	mtr_t*		mtr)	/*!< in: mtr */

{

	trx_upagef_t*	page_hdr;

	ulint		free;

	ulint		new_free;

	page_hdr = undo_page + TRX_UNDO_PAGE_HDR;

	free = mach_read_from_2(page_hdr + TRX_UNDO_PAGE_FREE);

	/* free is now the end offset of the old style undo log header */

	ut_a(free == (ulint)(log_hdr - undo_page) + TRX_UNDO_LOG_OLD_HDR_SIZE);

	new_free = free + (TRX_UNDO_LOG_XA_HDR_SIZE

			   - TRX_UNDO_LOG_OLD_HDR_SIZE);

	/* Add space for a XID after the header, update the free offset

	fields on the undo log page and in the undo log header */

	mlog_write_ulint(page_hdr + TRX_UNDO_PAGE_START, new_free,

			 MLOG_2BYTES, mtr);

	mlog_write_ulint(page_hdr + TRX_UNDO_PAGE_FREE, new_free,

			 MLOG_2BYTES, mtr);

	mlog_write_ulint(log_hdr + TRX_UNDO_LOG_START, new_free,

			 MLOG_2BYTES, mtr);

}

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

Writes the mtr log entry of an undo log header reuse. */

UNIV_INLINE

void

trx_undo_insert_header_reuse_log(

/*=============================*/

	const page_t*	undo_page,	/*!< in: undo log header page */

	trx_id_t	trx_id,		/*!< in: transaction id */

	mtr_t*		mtr)		/*!< in: mtr */

{

	mlog_write_initial_log_record(undo_page, MLOG_UNDO_HDR_REUSE, mtr);

	mlog_catenate_ull_compressed(mtr, trx_id);

}

#else /* !UNIV_HOTBACKUP */

# define trx_undo_insert_header_reuse_log(undo_page,trx_id,mtr) ((void) 0)

#endif /* !UNIV_HOTBACKUP */

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

Parses the redo log entry of an undo log page header create or reuse.

@return	end of log record or NULL */

UNIV_INTERN

byte*

trx_undo_parse_page_header(

/*=======================*/

	ulint	type,	/*!< in: MLOG_UNDO_HDR_CREATE or MLOG_UNDO_HDR_REUSE */

	byte*	ptr,	/*!< in: buffer */

	byte*	end_ptr,/*!< in: buffer end */

	page_t*	page,	/*!< in: page or NULL */

	mtr_t*	mtr)	/*!< in: mtr or NULL */

{

	trx_id_t	trx_id;

	/* Silence a GCC warning about possibly uninitialized variable

	when mach_ull_parse_compressed() is not inlined. */

	ut_d(trx_id = 0);

	/* Declare the variable uninitialized in Valgrind, so that the

	above initialization will not mask any bugs. */

	UNIV_MEM_INVALID(&trx_id, sizeof trx_id);

	ptr = mach_ull_parse_compressed(ptr, end_ptr, &trx_id);

	if (ptr == NULL) {

		return(NULL);

	}

	if (page) {

		if (type == MLOG_UNDO_HDR_CREATE) {

			trx_undo_header_create(page, trx_id, mtr);

		} else {

			ut_ad(type == MLOG_UNDO_HDR_REUSE);

			trx_undo_insert_header_reuse(page, trx_id, mtr);

		}

	}

	return(ptr);

}

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

Initializes a cached insert undo log header page for new use. NOTE that this

function has its own log record type MLOG_UNDO_HDR_REUSE. You must NOT change

the operation of this function!

@return	undo log header byte offset on page */

static

ulint

trx_undo_insert_header_reuse(

/*=========================*/

	page_t*		undo_page,	/*!< in/out: insert undo log segment

					header page, x-latched */

	trx_id_t	trx_id,		/*!< in: transaction id */

	mtr_t*		mtr)		/*!< in: mtr */

{

	trx_upagef_t*	page_hdr;

	trx_usegf_t*	seg_hdr;

	trx_ulogf_t*	log_hdr;

	ulint		free;

	ulint		new_free;

	ut_ad(mtr && undo_page);

	page_hdr = undo_page + TRX_UNDO_PAGE_HDR;

	seg_hdr = undo_page + TRX_UNDO_SEG_HDR;

	free = TRX_UNDO_SEG_HDR + TRX_UNDO_SEG_HDR_SIZE;

	ut_a(free + TRX_UNDO_LOG_XA_HDR_SIZE < UNIV_PAGE_SIZE - 100);

	log_hdr = undo_page + free;

	new_free = free + TRX_UNDO_LOG_OLD_HDR_SIZE;

	/* Insert undo data is not needed after commit: we may free all

	the space on the page */

	ut_a(mach_read_from_2(undo_page + TRX_UNDO_PAGE_HDR

			      + TRX_UNDO_PAGE_TYPE)

	     == TRX_UNDO_INSERT);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_START, new_free);

	mach_write_to_2(page_hdr + TRX_UNDO_PAGE_FREE, new_free);

	mach_write_to_2(seg_hdr + TRX_UNDO_STATE, TRX_UNDO_ACTIVE);

	log_hdr = undo_page + free;

	mach_write_to_8(log_hdr + TRX_UNDO_TRX_ID, trx_id);

	mach_write_to_2(log_hdr + TRX_UNDO_LOG_START, new_free);

	mach_write_to_1(log_hdr + TRX_UNDO_XID_EXISTS, FALSE);

	mach_write_to_1(log_hdr + TRX_UNDO_DICT_TRANS, FALSE);

	/* Write the log record MLOG_UNDO_HDR_REUSE */

	trx_undo_insert_header_reuse_log(undo_page, trx_id, mtr);

	return(free);

}

#ifndef UNIV_HOTBACKUP

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

Writes the redo log entry of an update undo log header discard. */

UNIV_INLINE

void

trx_undo_discard_latest_log(

/*========================*/

	page_t* undo_page,	/*!< in: undo log header page */

	mtr_t*	mtr)		/*!< in: mtr */

{

	mlog_write_initial_log_record(undo_page, MLOG_UNDO_HDR_DISCARD, mtr);

}

#else /* !UNIV_HOTBACKUP */

# define trx_undo_discard_latest_log(undo_page, mtr) ((void) 0)

#endif /* !UNIV_HOTBACKUP */

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

Parses the redo log entry of an undo log page header discard.

@return	end of log record or NULL */

UNIV_INTERN

byte*

trx_undo_parse_discard_latest(

/*==========================*/

	byte*	ptr,	/*!< in: buffer */

	byte*	end_ptr __attribute__((unused)), /*!< in: buffer end */

	page_t*	page,	/*!< in: page or NULL */

	mtr_t*	mtr)	/*!< in: mtr or NULL */

{

	ut_ad(end_ptr);

	if (page) {

		trx_undo_discard_latest_update_undo(page, mtr);

	}

	return(ptr);

}