InnoDB Plugin  1.0
buf_block_t Struct Reference

#include <buf0buf.h>

Collaboration diagram for buf_block_t:
Collaboration graph

Data Fields

General fields
buf_page_t page
byte * frame
ut_list_node< buf_block_tunzip_LRU
ibool in_unzip_LRU_list
ib_mutex_t mutex
rw_lock_t lock
unsigned lock_hash_val:32
ibool check_index_page_at_flush
Optimistic search field
ib_uint64_t modify_clock
Hash search fields (unprotected)

NOTE that these fields are NOT protected by any semaphore!

ulint n_hash_helps
ulint n_fields
ulint n_bytes
ibool left_side
Hash search fields

These 5 fields may only be modified when we have an x-latch on btr_search_latch AND

  • we are holding an s-latch or x-latch on buf_block_t::lock or
  • we know that buf_block_t::buf_fix_count == 0.

An exception to this is when we init or create a page in the buffer pool in

Another exception is that assigning block->index = NULL is allowed whenever holding an x-latch on btr_search_latch.

ulint n_pointers
unsigned curr_n_fields:10
unsigned curr_n_bytes:15
unsigned curr_left_side:1
Debug fields
rw_lock_t debug_latch

Detailed Description

The buffer control block structure

Field Documentation

ibool buf_block_t::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; NOT protected by any mutex

unsigned buf_block_t::curr_left_side

TRUE or FALSE in hash indexing

unsigned buf_block_t::curr_n_bytes

number of bytes in hash indexing

unsigned buf_block_t::curr_n_fields

prefix length for hash indexing: number of full fields

rw_lock_t buf_block_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

byte* buf_block_t::frame

pointer to buffer frame which is of size UNIV_PAGE_SIZE, and aligned to an address divisible by UNIV_PAGE_SIZE

ibool buf_block_t::in_unzip_LRU_list

TRUE if the page is in the decompressed LRU list; used in debugging

dict_index_t* buf_block_t::index

Index for which the adaptive hash index has been created, or NULL if the page does not exist in the index. Note that it does not guarantee that the index is complete, though: there may have been hash collisions, record deletions, etc.

ibool buf_block_t::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

rw_lock_t buf_block_t::lock

read-write lock of the buffer frame

unsigned buf_block_t::lock_hash_val

hashed value of the page address in the record lock hash table; protected by buf_block_t::lock (or buf_block_t::mutex, buf_pool->mutex in buf_page_get_gen(), buf_page_init_for_read() and buf_page_create())

ib_uint64_t buf_block_t::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

ib_mutex_t buf_block_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

ulint buf_block_t::n_bytes

recommended prefix: number of bytes in an incomplete field

ulint buf_block_t::n_fields

recommended prefix length for hash search: number of full fields

ulint buf_block_t::n_hash_helps

counter which controls building of a new hash index for the page

ulint buf_block_t::n_pointers

used in debugging: the number of pointers in the adaptive hash index pointing to this frame

buf_page_t buf_block_t::page

page information; this must be the first field, so that buf_pool->page_hash can point to buf_page_t or buf_block_t

ut_list_node< buf_block_t > buf_block_t::unzip_LRU

node of the decompressed LRU list; a block is in the unzip_LRU list if page.state == BUF_BLOCK_FILE_PAGE and != NULL

The documentation for this struct was generated from the following file: