~drizzle-trunk/drizzle/development

/*   Innobase relational database engine; Copyright (C) 2001 Innobase Oy

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

     it under the terms of the GNU General Public License 2

     as published by the Free Software Foundation in June 1991.

     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 2

     along with this program (in file COPYING); if not, write to the Free

     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

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

The database buffer pool high-level routines

(c) 1995 Innobase Oy

Created 11/5/1995 Heikki Tuuri

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

#ifndef buf0buf_h

#define buf0buf_h

#include "univ.i"

#include "fil0fil.h"

#include "mtr0types.h"

#include "buf0types.h"

#include "sync0rw.h"

#include "hash0hash.h"

#include "ut0byte.h"

#include "os0proc.h"

/* Flags for flush types */

#define BUF_FLUSH_LRU		1

#define BUF_FLUSH_SINGLE_PAGE	2

#define BUF_FLUSH_LIST		3	/* An array in the pool struct

					has size BUF_FLUSH_LIST + 1: if you

					add more flush types, put them in

					the middle! */

/* Modes for buf_page_get_gen */

#define BUF_GET			10	/* get always */

#define	BUF_GET_IF_IN_POOL	11	/* get if in pool */

#define	BUF_GET_NOWAIT		12	/* get if can set the latch without

					waiting */

#define BUF_GET_NO_LATCH	14	/* get and bufferfix, but set no latch;

					we have separated this case, because

					it is error-prone programming not to

					set a latch, and it should be used

					with care */

/* Modes for buf_page_get_known_nowait */

#define BUF_MAKE_YOUNG	51

#define BUF_KEEP_OLD	52

/* Magic value to use instead of checksums when they are disabled */

#define BUF_NO_CHECKSUM_MAGIC 0xDEADBEEFUL

extern buf_pool_t*	buf_pool;	/* The buffer pool of the database */

#ifdef UNIV_DEBUG

extern ibool		buf_debug_prints;/* If this is set TRUE, the program

					prints info whenever read or flush

					occurs */

#endif /* UNIV_DEBUG */

extern ulint srv_buf_pool_write_requests; /* variable to count write request

					  issued */

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

Creates the buffer pool. */

buf_pool_t*

buf_pool_init(

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

				/* out, own: buf_pool object, NULL if not

				enough memory or error */

	ulint	max_size,	/* in: maximum size of the buf_pool in

				blocks */

	ulint	curr_size,	/* in: current size to use, must be <=

				max_size, currently must be equal to

				max_size */

	ulint	n_frames);	/* in: number of frames; if AWE is used,

				this is the size of the address space window

				where physical memory pages are mapped; if

				AWE is not used then this must be the same

				as max_size */

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

Gets the current size of buffer buf_pool in bytes. In the case of AWE, the

size of AWE window (= the frames). */

UNIV_INLINE

ulint

buf_pool_get_curr_size(void);

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

			/* out: size in bytes */

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

Gets the maximum size of buffer pool in bytes. In the case of AWE, the

size of AWE window (= the frames). */

UNIV_INLINE

ulint

buf_pool_get_max_size(void);

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

			/* out: size in bytes */

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

Gets the smallest oldest_modification lsn for any page in the pool. Returns

ut_dulint_zero if all modified pages have been flushed to disk. */

UNIV_INLINE

dulint

buf_pool_get_oldest_modification(void);

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

				/* out: oldest modification in pool,

				ut_dulint_zero if none */

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

Allocates a buffer frame. */

buf_frame_t*

buf_frame_alloc(void);

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

				/* out: buffer frame */

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

Frees a buffer frame which does not contain a file page. */

void

buf_frame_free(

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

	buf_frame_t*	frame);	/* in: buffer frame */

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

Copies contents of a buffer frame to a given buffer. */

UNIV_INLINE

byte*

buf_frame_copy(

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

				/* out: buf */

	byte*		buf,	/* in: buffer to copy to */

	buf_frame_t*	frame);	/* in: buffer frame */

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

NOTE! The following macros should be used instead of buf_page_get_gen,

to improve debugging. Only values RW_S_LATCH and RW_X_LATCH are allowed

in LA! */

#define buf_page_get(SP, OF, LA, MTR)	 buf_page_get_gen(\

				SP, OF, LA, NULL,\

				BUF_GET, __FILE__, __LINE__, MTR)

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

Use these macros to bufferfix a page with no latching. Remember not to

read the contents of the page unless you know it is safe. Do not modify

the contents of the page! We have separated this case, because it is

error-prone programming not to set a latch, and it should be used

with care. */

#define buf_page_get_with_no_latch(SP, OF, MTR)	   buf_page_get_gen(\

				SP, OF, RW_NO_LATCH, NULL,\

				BUF_GET_NO_LATCH, __FILE__, __LINE__, MTR)

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

NOTE! The following macros should be used instead of buf_page_get_gen, to

improve debugging. Only values RW_S_LATCH and RW_X_LATCH are allowed as LA! */

#define buf_page_get_nowait(SP, OF, LA, MTR)	buf_page_get_gen(\

				SP, OF, LA, NULL,\

				BUF_GET_NOWAIT, __FILE__, __LINE__, MTR)

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

NOTE! The following macros should be used instead of

buf_page_optimistic_get_func, to improve debugging. Only values RW_S_LATCH and

RW_X_LATCH are allowed as LA! */

#define buf_page_optimistic_get(LA, BL, G, MC, MTR)			     \

	buf_page_optimistic_get_func(LA, BL, G, MC, __FILE__, __LINE__, MTR)

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

This is the general function used to get optimistic access to a database

page. */

ibool

buf_page_optimistic_get_func(

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

				/* out: TRUE if success */

	ulint		rw_latch,/* in: RW_S_LATCH, RW_X_LATCH */

	buf_block_t*	block,	/* in: guessed block */

	buf_frame_t*	guess,	/* in: guessed frame; note that AWE may move

				frames */

	dulint		modify_clock,/* in: modify clock value if mode is

				..._GUESS_ON_CLOCK */

	const char*	file,	/* in: file name */

	ulint		line,	/* in: line where called */

	mtr_t*		mtr);	/* in: mini-transaction */

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

Tries to get the page, but if file io is required, releases all latches

in mtr down to the given savepoint. If io is required, this function

retrieves the page to buffer buf_pool, but does not bufferfix it or latch

it. */

UNIV_INLINE

buf_frame_t*

buf_page_get_release_on_io(

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

				/* out: pointer to the frame, or NULL

				if not in buffer buf_pool */

	ulint	space,		/* in: space id */

	ulint	offset,		/* in: offset of the page within space

				in units of a page */

	buf_frame_t* guess,	/* in: guessed frame or NULL */

	ulint	rw_latch,	/* in: RW_X_LATCH, RW_S_LATCH,

				or RW_NO_LATCH */

	ulint	savepoint,	/* in: mtr savepoint */

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

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

This is used to get access to a known database page, when no waiting can be

done. */

ibool

buf_page_get_known_nowait(

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

				/* out: TRUE if success */

	ulint		rw_latch,/* in: RW_S_LATCH, RW_X_LATCH */

	buf_frame_t*	guess,	/* in: the known page frame */

	ulint		mode,	/* in: BUF_MAKE_YOUNG or BUF_KEEP_OLD */

	const char*	file,	/* in: file name */

	ulint		line,	/* in: line where called */

	mtr_t*		mtr);	/* in: mini-transaction */

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

This is the general function used to get access to a database page. */

buf_frame_t*

buf_page_get_gen(

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

				/* out: pointer to the frame or NULL */

	ulint		space,	/* in: space id */

	ulint		offset,	/* in: page number */

	ulint		rw_latch,/* in: RW_S_LATCH, RW_X_LATCH, RW_NO_LATCH */

	buf_frame_t*	guess,	/* in: guessed frame or NULL */

	ulint		mode,	/* in: BUF_GET, BUF_GET_IF_IN_POOL,

				BUF_GET_NO_LATCH */

	const char*	file,	/* in: file name */

	ulint		line,	/* in: line where called */

	mtr_t*		mtr);	/* in: mini-transaction */

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

Initializes a page to the buffer buf_pool. The page is usually not read

from a file even if it cannot be found in the buffer buf_pool. This is one

of the functions which perform to a block a state transition NOT_USED =>

FILE_PAGE (the other is buf_page_init_for_read above). */

buf_frame_t*

buf_page_create(

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

			/* out: pointer to the frame, page bufferfixed */

	ulint	space,	/* in: space id */

	ulint	offset,	/* in: offset of the page within space in units of

			a page */

	mtr_t*	mtr);	/* in: mini-transaction handle */

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

Inits a page to the buffer buf_pool, for use in ibbackup --restore. */

void

buf_page_init_for_backup_restore(

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

	ulint		space,	/* in: space id */

	ulint		offset,	/* in: offset of the page within space

				in units of a page */

	buf_block_t*	block);	/* in: block to init */

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

Decrements the bufferfix count of a buffer control block and releases

a latch, if specified. */

UNIV_INLINE

void

buf_page_release(

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

	buf_block_t*	block,		/* in: buffer block */

	ulint		rw_latch,	/* in: RW_S_LATCH, RW_X_LATCH,

					RW_NO_LATCH */

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

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

Moves a page to the start of the buffer pool LRU list. This high-level

function can be used to prevent an important page from from slipping out of

the buffer pool. */

void

buf_page_make_young(

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

	buf_frame_t*	frame);	/* in: buffer frame of a file page */

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

Returns TRUE if the page can be found in the buffer pool hash table. NOTE

that it is possible that the page is not yet read from disk, though. */

ibool

buf_page_peek(

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

			/* out: TRUE if found from page hash table,

			NOTE that the page is not necessarily yet read

			from disk! */

	ulint	space,	/* in: space id */

	ulint	offset);/* in: page number */

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

Returns the buffer control block if the page can be found in the buffer

pool. NOTE that it is possible that the page is not yet read

from disk, though. This is a very low-level function: use with care! */

buf_block_t*

buf_page_peek_block(

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

			/* out: control block if found from page hash table,

			otherwise NULL; NOTE that the page is not necessarily

			yet read from disk! */

	ulint	space,	/* in: space id */

	ulint	offset);/* in: page number */

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

Resets the check_index_page_at_flush field of a page if found in the buffer

pool. */

void

buf_reset_check_index_page_at_flush(

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

	ulint	space,	/* in: space id */

	ulint	offset);/* in: page number */

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

Sets file_page_was_freed TRUE if the page is found in the buffer pool.

This function should be called when we free a file page and want the

debug version to check that it is not accessed any more unless

reallocated. */

buf_block_t*

buf_page_set_file_page_was_freed(

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

			/* out: control block if found from page hash table,

			otherwise NULL */

	ulint	space,	/* in: space id */

	ulint	offset);	/* in: page number */

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

Sets file_page_was_freed FALSE if the page is found in the buffer pool.

This function should be called when we free a file page and want the

debug version to check that it is not accessed any more unless

reallocated. */

buf_block_t*

buf_page_reset_file_page_was_freed(

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

			/* out: control block if found from page hash table,

			otherwise NULL */

	ulint	space,	/* in: space id */

	ulint	offset);	/* in: page number */

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

Recommends a move of a block to the start of the LRU list if there is danger

of dropping from the buffer pool. NOTE: does not reserve the buffer pool

mutex. */

UNIV_INLINE

ibool

buf_block_peek_if_too_old(

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

				/* out: TRUE if should be made younger */

	buf_block_t*	block);	/* in: block to make younger */

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

Returns the current state of is_hashed of a page. FALSE if the page is

not in the pool. NOTE that this operation does not fix the page in the

pool if it is found there. */

ibool

buf_page_peek_if_search_hashed(

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

			/* out: TRUE if page hash index is built in search

			system */

	ulint	space,	/* in: space id */

	ulint	offset);/* in: page number */

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

Gets the youngest modification log sequence number for a frame.

Returns zero if not file page or no modification occurred yet. */

UNIV_INLINE

dulint

buf_frame_get_newest_modification(

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

				/* out: newest modification to page */

	buf_frame_t*	frame);	/* in: pointer to a frame */

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

Increments the modify clock of a frame by 1. The caller must (1) own the

pool mutex and block bufferfix count has to be zero, (2) or own an x-lock

on the block. */

UNIV_INLINE

dulint

buf_frame_modify_clock_inc(

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

				/* out: new value */

	buf_frame_t*	frame);	/* in: pointer to a frame */

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

Increments the modify clock of a frame by 1. The caller must (1) own the

buf_pool mutex and block bufferfix count has to be zero, (2) or own an x-lock

on the block. */

UNIV_INLINE

dulint

buf_block_modify_clock_inc(

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

				/* out: new value */

	buf_block_t*	block);	/* in: block */

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

Returns the value of the modify clock. The caller must have an s-lock

or x-lock on the block. */

UNIV_INLINE

dulint

buf_block_get_modify_clock(

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

				/* out: value */

	buf_block_t*	block);	/* in: block */

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

Calculates a page checksum which is stored to the page when it is written

to a file. Note that we must be careful to calculate the same value

on 32-bit and 64-bit architectures. */

ulint

buf_calc_page_new_checksum(

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

			/* out: checksum */

	byte*	page);	/* in: buffer page */

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

In versions < 4.0.14 and < 4.1.1 there was a bug that the checksum only

looked at the first few bytes of the page. This calculates that old

checksum.

NOTE: we must first store the new formula checksum to

FIL_PAGE_SPACE_OR_CHKSUM before calculating and storing this old checksum

because this takes that field as an input! */

ulint

buf_calc_page_old_checksum(

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

			/* out: checksum */

	byte*	 page);	/* in: buffer page */

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

Checks if a page is corrupt. */

ibool

buf_page_is_corrupted(

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

				/* out: TRUE if corrupted */

	byte*	read_buf);	/* in: a database page */

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

Gets the page number of a pointer pointing within a buffer frame containing

a file page. */

UNIV_INLINE

ulint

buf_frame_get_page_no(

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

			/* out: page number */

	byte*	ptr);	/* in: pointer to within a buffer frame */

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

Gets the space id of a pointer pointing within a buffer frame containing a

file page. */

UNIV_INLINE

ulint

buf_frame_get_space_id(

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

			/* out: space id */

	byte*	ptr);	/* in: pointer to within a buffer frame */

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

Gets the space id, page offset, and byte offset within page of a

pointer pointing to a buffer frame containing a file page. */

UNIV_INLINE

void

buf_ptr_get_fsp_addr(

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

	byte*		ptr,	/* in: pointer to a buffer frame */

	ulint*		space,	/* out: space id */

	fil_addr_t*	addr);	/* out: page offset and byte offset */

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

Gets the hash value of the page the pointer is pointing to. This can be used

in searches in the lock hash table. */

UNIV_INLINE

ulint

buf_frame_get_lock_hash_val(

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

			/* out: lock hash value */

	byte*	ptr);	/* in: pointer to within a buffer frame */

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

Gets the mutex number protecting the page record lock hash chain in the lock

table. */

UNIV_INLINE

mutex_t*

buf_frame_get_mutex(

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

			/* out: mutex */

	byte*	ptr);	/* in: pointer to within a buffer frame */

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

Gets the frame the pointer is pointing to. */

UNIV_INLINE

buf_frame_t*

buf_frame_align(

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

			/* out: pointer to frame */

	byte*	ptr);	/* in: pointer to a frame */

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

Checks if a pointer points to the block array of the buffer pool (blocks, not

the frames). */

UNIV_INLINE

ibool

buf_pool_is_block(

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

			/* out: TRUE if pointer to block */

	void*	ptr);	/* in: pointer to memory */

#ifdef UNIV_DEBUG

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

Validates the buffer pool data structure. */

ibool

buf_validate(void);

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

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

Prints info of the buffer pool data structure. */

void

buf_print(void);

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

#endif /* UNIV_DEBUG */

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

Prints a page to stderr. */

void

buf_page_print(

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

	byte*	read_buf);	/* in: a database page */

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

Returns the number of latched pages in the buffer pool. */

ulint

buf_get_latched_pages_number(void);

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

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

Returns the number of pending buf pool ios. */

ulint

buf_get_n_pending_ios(void);

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

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

Prints info of the buffer i/o. */

void

buf_print_io(

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

	FILE*	file);	/* in: file where to print */

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

Returns the ratio in percents of modified pages in the buffer pool /

database pages in the buffer pool. */

ulint

buf_get_modified_ratio_pct(void);

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

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

Refreshes the statistics used to print per-second averages. */

void

buf_refresh_io_stats(void);

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

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

Checks that all file pages in the buffer are in a replaceable state. */

ibool

buf_all_freed(void);

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

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

Checks that there currently are no pending i/o-operations for the buffer

pool. */

ibool

buf_pool_check_no_pending_io(void);

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

				/* out: TRUE if there is no pending i/o */

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

Invalidates the file pages in the buffer pool when an archive recovery is

completed. All the file pages buffered must be in a replaceable state when

this function is called: not latched and not modified. */

void

buf_pool_invalidate(void);

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

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

--------------------------- LOWER LEVEL ROUTINES -------------------------

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

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

Maps the page of block to a frame, if not mapped yet. Unmaps some page

from the end of the awe_LRU_free_mapped. */

void

buf_awe_map_page_to_frame(

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

	buf_block_t*	block,		/* in: block whose page should be

					mapped to a frame */

	ibool		add_to_mapped_list);/* in: TRUE if we in the case

					we need to map the page should also

					add the block to the

					awe_LRU_free_mapped list */

#ifdef UNIV_SYNC_DEBUG

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

Adds latch level info for the rw-lock protecting the buffer frame. This

should be called in the debug version after a successful latching of a

page if we know the latching order level of the acquired latch. */

UNIV_INLINE

void

buf_page_dbg_add_level(

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

	buf_frame_t*	frame,	/* in: buffer page where we have acquired

				a latch */

	ulint		level);	/* in: latching order level */

#endif /* UNIV_SYNC_DEBUG */

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

Gets a pointer to the memory frame of a block. */

UNIV_INLINE

buf_frame_t*

buf_block_get_frame(

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

				/* out: pointer to the frame */

	buf_block_t*	block);	/* in: pointer to the control block */

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

Gets the space id of a block. */

UNIV_INLINE

ulint

buf_block_get_space(

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

				/* out: space id */

	buf_block_t*	block);	/* in: pointer to the control block */

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

Gets the page number of a block. */

UNIV_INLINE

ulint

buf_block_get_page_no(

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

				/* out: page number */

	buf_block_t*	block);	/* in: pointer to the control block */

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

Gets the block to whose frame the pointer is pointing to. */

UNIV_INLINE

buf_block_t*

buf_block_align(

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

			/* out: pointer to block */

	byte*	ptr);	/* in: pointer to a frame */

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

This function is used to get info if there is an io operation

going on on a buffer page. */

UNIV_INLINE

ibool

buf_page_io_query(

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

				/* out: TRUE if io going on */

	buf_block_t*	block);	/* in: pool block, must be bufferfixed */

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

Accessor function for block array. */

UNIV_INLINE

buf_block_t*

buf_pool_get_nth_block(

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

				/* out: pointer to block */

	buf_pool_t*	pool,	/* in: pool */

	ulint		i);	/* in: index of the block */

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

Function which inits a page for read to the buffer buf_pool. If the page is

(1) already in buf_pool, or

(2) if we specify to read only ibuf pages and the page is not an ibuf page, or

(3) if the space is deleted or being deleted,

then this function does nothing.

Sets the io_fix flag to BUF_IO_READ and sets a non-recursive exclusive lock

on the buffer frame. The io-handler must take care that the flag is cleared

and the lock released later. This is one of the functions which perform the

state transition NOT_USED => FILE_PAGE to a block (the other is

buf_page_create). */

buf_block_t*

buf_page_init_for_read(

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

				/* out: pointer to the block or NULL */

	ulint*		err,	/* out: DB_SUCCESS or DB_TABLESPACE_DELETED */

	ulint		mode,	/* in: BUF_READ_IBUF_PAGES_ONLY, ... */

	ulint		space,	/* in: space id */

	ib_longlong	tablespace_version,/* in: prevents reading from a wrong

				version of the tablespace in case we have done

				DISCARD + IMPORT */

	ulint		offset);/* in: page number */

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

Completes an asynchronous read or write request of a file page to or from

the buffer pool. */

void

buf_page_io_complete(

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

	buf_block_t*	block);	/* in: pointer to the block in question */

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

Calculates a folded value of a file page address to use in the page hash

table. */

UNIV_INLINE

ulint

buf_page_address_fold(

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

			/* out: the folded value */

	ulint	space,	/* in: space id */

	ulint	offset);/* in: offset of the page within space */

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

Returns the control block of a file page, NULL if not found. */

UNIV_INLINE

buf_block_t*

buf_page_hash_get(

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

			/* out: block, NULL if not found */

	ulint	space,	/* in: space id */

	ulint	offset);/* in: offset of the page within space */

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

Increments the pool clock by one and returns its new value. Remember that

in the 32 bit version the clock wraps around at 4 billion! */

UNIV_INLINE

ulint

buf_pool_clock_tic(void);

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

			/* out: new clock value */

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

Gets the current length of the free list of buffer blocks. */

ulint

buf_get_free_list_len(void);

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

/* The buffer control block structure */

struct buf_block_struct{

	/* 1. General fields */

	ulint		magic_n;	/* magic number to check */

	ulint		state;		/* state of the control block:

					BUF_BLOCK_NOT_USED, ...; changing

					this is only allowed when a thread

					has BOTH the buffer pool mutex AND

					block->mutex locked */

	byte*		frame;		/* pointer to buffer frame which

					is of size UNIV_PAGE_SIZE, and

					aligned to an address divisible by

					UNIV_PAGE_SIZE; if AWE is used, this

					will be NULL for the pages which are

					currently not mapped into the virtual

					address space window of the buffer

					pool */

	os_awe_t*	awe_info;	/* if AWE is used, then an array of

					awe page infos for

					UNIV_PAGE_SIZE / OS_AWE_X86_PAGE_SIZE

					(normally = 4) physical memory

					pages; otherwise NULL */

	ulint		space;		/* space id of the page */

	ulint		offset;		/* page number within the space */

	ulint		lock_hash_val;	/* hashed value of the page address

					in the record lock hash table */

	mutex_t		mutex;		/* mutex protecting this block:

					state (also protected by the buffer

					pool mutex), io_fix, buf_fix_count,

					and accessed; we introduce this new

					mutex in InnoDB-5.1 to relieve

					contention on the buffer pool mutex */

	rw_lock_t	lock;		/* read-write lock of the buffer

					frame */

	buf_block_t*	hash;		/* node used in chaining to the page

					hash table */

	ibool		check_index_page_at_flush;

					/* TRUE if we know that this is

					an index page, and want the database

					to check its consistency before flush;

					note that there may be pages in the

					buffer pool which are index pages,

					but this flag is not set because

					we do not keep track of all pages */

	/* 2. Page flushing fields */

	UT_LIST_NODE_T(buf_block_t) flush_list;

					/* node of the modified, not yet

					flushed blocks list */

	dulint		newest_modification;

					/* log sequence number of the youngest

					modification to this block, zero if

					not modified */

	dulint		oldest_modification;

					/* log sequence number of the START of

					the log entry written of the oldest

					modification to this block which has

					not yet been flushed on disk; zero if

					all modifications are on disk */

	ulint		flush_type;	/* if this block is currently being

					flushed to disk, this tells the

					flush_type: BUF_FLUSH_LRU or

					BUF_FLUSH_LIST */

	/* 3. LRU replacement algorithm fields */

	UT_LIST_NODE_T(buf_block_t) free;

					/* node of the free block list */

	ibool		in_free_list;	/* TRUE if in the free list; used in

					debugging */

	UT_LIST_NODE_T(buf_block_t) LRU;

					/* node of the LRU list */

	UT_LIST_NODE_T(buf_block_t) awe_LRU_free_mapped;

					/* in the AWE version node in the

					list of free and LRU blocks which are

					mapped to a frame */

	ibool		in_LRU_list;	/* TRUE of the page is in the LRU list;

					used in debugging */

	ulint		LRU_position;	/* value which monotonically

					decreases (or may stay constant if

					the block is in the old blocks) toward

					the end of the LRU list, if the pool

					ulint_clock has not wrapped around:

					NOTE that this value can only be used

					in heuristic algorithms, because of

					the possibility of a wrap-around! */

	ulint		freed_page_clock;/* the value of freed_page_clock

					of the buffer pool when this block was

					the last time put to the head of the

					LRU list; a thread is allowed to

					read this for heuristic purposes

					without holding any mutex or latch */

	ibool		old;		/* TRUE if the block is in the old

					blocks in the LRU list */

	ibool		accessed;	/* TRUE if the page has been accessed

					while in the buffer pool: read-ahead

					may read in pages which have not been

					accessed yet; this is protected by

					block->mutex; a thread is allowed to

					read this for heuristic purposes

					without holding any mutex or latch */

	ulint		buf_fix_count;	/* count of how manyfold this block

					is currently bufferfixed; this is

					protected by block->mutex */

	ulint		io_fix;		/* if a read is pending to the frame,

					io_fix is BUF_IO_READ, in the case

					of a write BUF_IO_WRITE, otherwise 0;

					this is protected by block->mutex */

	/* 4. Optimistic search field */

	dulint		modify_clock;	/* this clock is incremented every

					time a pointer to a record on the

					page may become obsolete; this is

					used in the optimistic cursor

					positioning: if the modify clock has

					not changed, we know that the pointer

					is still valid; this field may be

					changed if the thread (1) owns the

					pool mutex and the page is not

					bufferfixed, or (2) the thread has an

					x-latch on the block */

	/* 5. Hash search fields: NOTE that the first 4 fields are NOT

	protected by any semaphore! */

	ulint		n_hash_helps;	/* counter which controls building

					of a new hash index for the page */

	ulint		n_fields;	/* recommended prefix length for hash

					search: number of full fields */

	ulint		n_bytes;	/* recommended prefix: number of bytes

					in an incomplete field */

	ibool		left_side;	/* TRUE or FALSE, depending on

					whether the leftmost record of several

					records with the same prefix should be

					indexed in the hash index */

	/* These 6 fields may only be modified when we have

	an x-latch on btr_search_latch AND

	a) we are holding an s-latch or x-latch on block->lock or

	b) we know that block->buf_fix_count == 0.

	An exception to this is when we init or create a page

	in the buffer pool in buf0buf.c. */

	ibool		is_hashed;	/* TRUE if hash index has already been

					built on this page; note that it does

					not guarantee that the index is

					complete, though: there may have been

					hash collisions, record deletions,

					etc. */

	ulint		n_pointers;	/* used in debugging: the number of

					pointers in the adaptive hash index

					pointing to this frame */

	ulint		curr_n_fields;	/* prefix length for hash indexing:

					number of full fields */

	ulint		curr_n_bytes;	/* number of bytes in hash indexing */

	ibool		curr_left_side;	/* TRUE or FALSE in hash indexing */

	dict_index_t*	index;		/* Index for which the adaptive

					hash index has been created. */

	/* 6. Debug fields */

#ifdef UNIV_SYNC_DEBUG

	rw_lock_t	debug_latch;	/* in the debug version, each thread

					which bufferfixes the block acquires

					an s-latch here; so we can use the

					debug utilities in sync0rw */

#endif

	ibool		file_page_was_freed;

					/* this is set to TRUE when fsp

					frees a page in buffer pool */

};

#define BUF_BLOCK_MAGIC_N	41526563

/* The buffer pool structure. NOTE! The definition appears here only for

other modules of this directory (buf) to see it. Do not use from outside! */

struct buf_pool_struct{

	/* 1. General fields */

	mutex_t		mutex;		/* mutex protecting the buffer pool

					struct and control blocks, except the

					read-write lock in them */

	byte*		frame_mem;	/* pointer to the memory area which

					was allocated for the frames; in AWE

					this is the virtual address space

					window where we map pages stored

					in physical memory */

	byte*		frame_zero;	/* pointer to the first buffer frame:

					this may differ from frame_mem, because

					this is aligned by the frame size */

	byte*		high_end;	/* pointer to the end of the buffer

					frames */

	ulint		n_frames;	/* number of frames */

	buf_block_t*	blocks;		/* array of buffer control blocks */

	buf_block_t**	blocks_of_frames;/* inverse mapping which can be used

					to retrieve the buffer control block

					of a frame; this is an array which

					lists the blocks of frames in the

					order frame_zero,

					frame_zero + UNIV_PAGE_SIZE, ...

					a control block is always assigned

					for each frame, even if the frame does

					not contain any data; note that in AWE

					there are more control blocks than

					buffer frames */

	os_awe_t*	awe_info;	/* if AWE is used, AWE info for the

					physical 4 kB memory pages associated

					with buffer frames */

	ulint		max_size;	/* number of control blocks ==

					maximum pool size in pages */

	ulint		curr_size;	/* current pool size in pages;

					currently always the same as

					max_size */

	hash_table_t*	page_hash;	/* hash table of the file pages */

	ulint		n_pend_reads;	/* number of pending read operations */

	time_t		last_printout_time; /* when buf_print was last time

					called */

	ulint		n_pages_read;	/* number read operations */

	ulint		n_pages_written;/* number write operations */

	ulint		n_pages_created;/* number of pages created in the pool

					with no read */

	ulint		n_page_gets;	/* number of page gets performed;

					also successful searches through

					the adaptive hash index are

					counted as page gets; this field

					is NOT protected by the buffer

					pool mutex */

	ulint		n_pages_awe_remapped; /* if AWE is enabled, the

					number of remaps of blocks to

					buffer frames */

	ulint		n_page_gets_old;/* n_page_gets when buf_print was

					last time called: used to calculate

					hit rate */

	ulint		n_pages_read_old;/* n_pages_read when buf_print was

					last time called */

	ulint		n_pages_written_old;/* number write operations */

	ulint		n_pages_created_old;/* number of pages created in

					the pool with no read */

	ulint		n_pages_awe_remapped_old;

	/* 2. Page flushing algorithm fields */

	UT_LIST_BASE_NODE_T(buf_block_t) flush_list;

					/* base node of the modified block

					list */

	ibool		init_flush[BUF_FLUSH_LIST + 1];

					/* this is TRUE when a flush of the

					given type is being initialized */

	ulint		n_flush[BUF_FLUSH_LIST + 1];

					/* this is the number of pending

					writes in the given flush type */

	os_event_t	no_flush[BUF_FLUSH_LIST + 1];

					/* this is in the set state when there

					is no flush batch of the given type

					running */

	ulint		ulint_clock;	/* a sequence number used to count

					time. NOTE! This counter wraps

					around at 4 billion (if ulint ==

					32 bits)! */

	ulint		freed_page_clock;/* a sequence number used to count the

					number of buffer blocks removed from

					the end of the LRU list; NOTE that

					this counter may wrap around at 4

					billion! A thread is allowed to

					read this for heuristic purposes

					without holding any mutex or latch */

	ulint		LRU_flush_ended;/* when an LRU flush ends for a page,

					this is incremented by one; this is

					set to zero when a buffer block is

					allocated */

	/* 3. LRU replacement algorithm fields */

	UT_LIST_BASE_NODE_T(buf_block_t) free;

					/* base node of the free block list;

					in the case of AWE, at the start are

					always free blocks for which the

					physical memory is mapped to a frame */

	UT_LIST_BASE_NODE_T(buf_block_t) LRU;

					/* base node of the LRU list */

	buf_block_t*	LRU_old;	/* pointer to the about 3/8 oldest

					blocks in the LRU list; NULL if LRU

					length less than BUF_LRU_OLD_MIN_LEN */

	ulint		LRU_old_len;	/* length of the LRU list from

					the block to which LRU_old points

					onward, including that block;

					see buf0lru.c for the restrictions

					on this value; not defined if

					LRU_old == NULL */

	UT_LIST_BASE_NODE_T(buf_block_t) awe_LRU_free_mapped;

					/* list of those blocks which are

					in the LRU list or the free list, and

					where the page is mapped to a frame;

					thus, frames allocated, e.g., to the

					locki table, are not in this list */

};

/* States of a control block */

#define	BUF_BLOCK_NOT_USED	211	/* is in the free list */

#define BUF_BLOCK_READY_FOR_USE	212	/* when buf_get_free_block returns

					a block, it is in this state */

#define	BUF_BLOCK_FILE_PAGE	213	/* contains a buffered file page */

#define	BUF_BLOCK_MEMORY	214	/* contains some main memory object */

#define BUF_BLOCK_REMOVE_HASH	215	/* hash index should be removed

					before putting to the free list */

/* Io_fix states of a control block; these must be != 0 */

#define BUF_IO_READ		561

#define BUF_IO_WRITE		562

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

Let us list the consistency conditions for different control block states.

NOT_USED:	is in free list, not in LRU list, not in flush list, nor

		page hash table

READY_FOR_USE:	is not in free list, LRU list, or flush list, nor page

		hash table

MEMORY:		is not in free list, LRU list, or flush list, nor page

		hash table

FILE_PAGE:	space and offset are defined, is in page hash table

		if io_fix == BUF_IO_WRITE,

			pool: no_flush[block->flush_type] is in reset state,

			pool: n_flush[block->flush_type] > 0

		(1) if buf_fix_count == 0, then

			is in LRU list, not in free list

			is in flush list,

				if and only if oldest_modification > 0