/* 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" #include "page0types.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 */ /* States of a control block */ enum buf_block_state { BUF_BLOCK_NOT_USED = 211, /* is in the free list */ BUF_BLOCK_READY_FOR_USE, /* when buf_get_free_block returns a block, it is in this state */ BUF_BLOCK_FILE_PAGE, /* contains a buffered file page */ BUF_BLOCK_MEMORY, /* contains some main memory object */ BUF_BLOCK_REMOVE_HASH /* hash index should be removed before putting to the free list */ }; /************************************************************************ Creates the buffer pool. */ buf_pool_t* buf_pool_init(void); /*===============*/ /* out, own: buf_pool object, NULL if not enough memory or error */ /************************************************************************ Resizes the buffer pool. */ void buf_pool_resize(void); /*=================*/ /************************************************************************* Gets the current size of buffer buf_pool in bytes. */ UNIV_INLINE ulint buf_pool_get_curr_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 block. */ UNIV_INLINE buf_block_t* buf_block_alloc( /*============*/ /* out, own: the allocated block */ ulint zip_size); /* in: compressed page size in bytes, or 0 if uncompressed tablespace */ /************************************************************************ Frees a buffer block which does not contain a file page. */ UNIV_INLINE void buf_block_free( /*===========*/ buf_block_t* block); /* in, own: block to be freed */ /************************************************************************* 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 */ const 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, MC, MTR) \ buf_page_optimistic_get_func(LA, BL, 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 */ 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_block_t* buf_page_get_release_on_io( /*=======================*/ /* out: pointer to the block, 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_block_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_block_t* block, /* in: the known page */ 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_block_t* buf_page_get_gen( /*=============*/ /* out: pointer to the block 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_block_t* guess, /* in: guessed block 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_block_t* buf_page_create( /*============*/ /* out: pointer to the block, page bufferfixed */ ulint space, /* in: space id */ ulint offset, /* in: offset of the page within space in units of a page */ ulint zip_size,/* in: compressed page size, or 0 */ mtr_t* mtr); /* in: mini-transaction handle */ #ifdef UNIV_HOTBACKUP /************************************************************************ 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 */ ulint zip_size,/* in: compressed page size in bytes or 0 for uncompressed pages */ buf_block_t* block); /* in: block to init */ #endif /* UNIV_HOTBACKUP */ /************************************************************************ 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_block_t* block); /* in: buffer block 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 */ #ifdef UNIV_DEBUG_FILE_ACCESSES /************************************************************************ 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 */ #endif /* UNIV_DEBUG_FILE_ACCESSES */ /************************************************************************ 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_block_get_newest_modification( /*==============================*/ /* out: newest modification to page */ buf_block_t* block); /* in: block containing the page 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 void buf_block_modify_clock_inc( /*=======================*/ 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 */ const 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 */ const byte* page); /* in: buffer page */ /************************************************************************ Checks if a page is corrupt. */ ibool buf_page_is_corrupted( /*==================*/ /* out: TRUE if corrupted */ const byte* read_buf, /* in: a database page */ ulint zip_size); /* in: size of compressed page; 0 for uncompressed pages */ /************************************************************************** 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( /*=================*/ const void* 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 a block. This can be used in searches in the lock hash table. */ UNIV_INLINE ulint buf_block_get_lock_hash_val( /*========================*/ /* out: lock hash value */ const buf_block_t* block) /* in: block */ __attribute__((const)); #if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG /************************************************************************* Validates the buffer pool data structure. */ ibool buf_validate(void); /*==============*/ #endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */ #if defined UNIV_DEBUG_PRINT || defined UNIV_DEBUG || defined UNIV_BUF_DEBUG /************************************************************************* Prints info of the buffer pool data structure. */ void buf_print(void); /*============*/ #endif /* UNIV_DEBUG_PRINT || UNIV_DEBUG || UNIV_BUF_DEBUG */ /************************************************************************ Prints a page to stderr. */ void buf_page_print( /*===========*/ const byte* read_buf, /* in: a database page */ ulint zip_size); /* in: compressed page size, or 0 for uncompressed pages */ /************************************************************************* 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 ------------------------- =========================================================================*/ #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_block_dbg_add_level( /*====================*/ buf_block_t* block, /* in: buffer page where we have acquired latch */ ulint level); /* in: latching order level */ #endif /* UNIV_SYNC_DEBUG */ /************************************************************************* Gets the state of a block. */ UNIV_INLINE enum buf_block_state buf_block_get_state( /*================*/ /* out: state */ const buf_block_t* block) /* in: pointer to the control block */ __attribute__((pure)); /************************************************************************* 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 */ __attribute__((const)); /************************************************************************* Gets the space id of a block. */ UNIV_INLINE ulint buf_block_get_space( /*================*/ /* out: space id */ const buf_block_t* block) /* in: pointer to the control block */ __attribute((const)); /************************************************************************* Gets the page number of a block. */ UNIV_INLINE ulint buf_block_get_page_no( /*==================*/ /* out: page number */ const buf_block_t* block) /* in: pointer to the control block */ __attribute((const)); /************************************************************************* Gets the compressed page size of a block. */ UNIV_INLINE ulint buf_block_get_zip_size( /*===================*/ /* out: compressed page size, or 0 */ const buf_block_t* block) /* in: pointer to the control block */ __attribute((const)); /************************************************************************* Gets the compressed page descriptor corresponding to an uncompressed page if applicable. */ UNIV_INLINE page_zip_des_t* buf_block_get_page_zip( /*===================*/ /* out: compressed page descriptor, or NULL */ buf_block_t* block) /* in: pointer to the control block */ __attribute((const)); #if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG /*********************************************************************** 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 */ /************************************************************************* Gets the compressed page descriptor corresponding to an uncompressed page if applicable. */ UNIV_INLINE page_zip_des_t* buf_frame_get_page_zip( /*===================*/ /* out: compressed page descriptor, or NULL */ byte* ptr) /* in: pointer to the page */ __attribute((const)); #endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */ /************************************************************************ 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 */ /************************************************************************ 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 */ ulint zip_size,/* in: compressed page size, or 0 */ 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 */ 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 */ 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. */ #ifdef UNIV_DEBUG ulint n_pointers; /* used in debugging: the number of pointers in the adaptive hash index pointing to this frame */ #endif /* UNIV_DEBUG */ 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. */ /* TODO: how to protect this? */ page_zip_des_t page_zip; /* compressed page info */ /* 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 #ifdef UNIV_DEBUG_FILE_ACCESSES ibool file_page_was_freed; /* this is set to TRUE when fsp frees a page in buffer pool */ #endif /* UNIV_DEBUG_FILE_ACCESSES */ }; #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 */ ulint n_chunks; /* number of buffer pool chunks */ buf_chunk_t* chunks; /* buffer pool chunks */ ulint curr_size; /* current pool size in pages */ 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_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 */ /* 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 */ 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 */ }; /* 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 is x-locked, if and only if io_fix == BUF_IO_READ is s-locked, if and only if io_fix == BUF_IO_WRITE (2) if buf_fix_count > 0, then is not in LRU list, not in free list is in flush list, if and only if oldest_modification > 0 if io_fix == BUF_IO_READ, is x-locked if io_fix == BUF_IO_WRITE, is s-locked State transitions: NOT_USED => READY_FOR_USE READY_FOR_USE => MEMORY READY_FOR_USE => FILE_PAGE MEMORY => NOT_USED FILE_PAGE => NOT_USED NOTE: This transition is allowed if and only if (1) buf_fix_count == 0, (2) oldest_modification == 0, and (3) io_fix == 0. */ #ifndef UNIV_NONINL #include "buf0buf.ic" #endif #endif