Drizzled Public API Documentation

buf0rea.h File Reference
#include "univ.i"
#include "buf0types.h"

Go to the source code of this file.

Defines

#define BUF_READ_AHEAD_AREA(b)   ut_min(64, ut_2_power_up((b)->curr_size / 32))
Modes used in read-ahead @{
#define BUF_READ_IBUF_PAGES_ONLY   131
#define BUF_READ_ANY_PAGE   132

Functions

UNIV_INTERN ibool buf_read_page (ulint space, ulint zip_size, ulint offset)
UNIV_INTERN ulint buf_read_ahead_linear (ulint space, ulint zip_size, ulint offset)
UNIV_INTERN void buf_read_ibuf_merge_pages (ibool sync, const ulint *space_ids, const ib_int64_t *space_versions, const ulint *page_nos, ulint n_stored)
UNIV_INTERN void buf_read_recv_pages (ibool sync, ulint space, ulint zip_size, const ulint *page_nos, ulint n_stored)

Detailed Description

The database buffer read

Created 11/5/1995 Heikki Tuuri

Definition in file buf0rea.h.


Define Documentation

#define BUF_READ_AHEAD_AREA (   b)    ut_min(64, ut_2_power_up((b)->curr_size / 32))

The size in pages of the area which the read-ahead algorithms read if invoked

Definition at line 128 of file buf0rea.h.

Referenced by buf_read_ahead_linear().

#define BUF_READ_ANY_PAGE   132
#define BUF_READ_IBUF_PAGES_ONLY   131

read only pages belonging to the insert buffer tree

Definition at line 133 of file buf0rea.h.

Referenced by buf_page_init_for_read(), and buf_read_ahead_linear().


Function Documentation

UNIV_INTERN ulint buf_read_ahead_linear ( ulint  space,
ulint  zip_size,
ulint  offset 
)

Applies linear read-ahead if in the buf_pool the page is a border page of a linear read-ahead area and all the pages in the area have been accessed. Does not read any page if the read-ahead mechanism is not activated. Note that the the algorithm looks at the 'natural' adjacent successor and predecessor of the page, which on the leaf level of a B-tree are the next and previous page in the chain of leaves. To know these, the page specified in (space, offset) must already be present in the buf_pool. Thus, the natural way to use this function is to call it when a page in the buf_pool is accessed the first time, calling this function just after it has been bufferfixed. NOTE 1: as this function looks at the natural predecessor and successor fields on the page, what happens, if these are not initialized to any sensible value? No problem, before applying read-ahead we check that the area to read is within the span of the space, if not, read-ahead is not applied. An uninitialized value may result in a useless read operation, but only very improbably. NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this function must be written such that it cannot end up waiting for these latches! NOTE 3: the calling thread must want access to the page given: this rule is set to prevent unintended read-aheads performed by ibuf routines, a situation which could result in a deadlock if the OS does not support asynchronous io.

Returns:
number of page read requests issued in: page number of a page; NOTE: the current thread must want access to this page (see NOTE 3 above)

Applies linear read-ahead if in the buf_pool the page is a border page of a linear read-ahead area and all the pages in the area have been accessed. Does not read any page if the read-ahead mechanism is not activated. Note that the the algorithm looks at the 'natural' adjacent successor and predecessor of the page, which on the leaf level of a B-tree are the next and previous page in the chain of leaves. To know these, the page specified in (space, offset) must already be present in the buf_pool. Thus, the natural way to use this function is to call it when a page in the buf_pool is accessed the first time, calling this function just after it has been bufferfixed. NOTE 1: as this function looks at the natural predecessor and successor fields on the page, what happens, if these are not initialized to any sensible value? No problem, before applying read-ahead we check that the area to read is within the span of the space, if not, read-ahead is not applied. An uninitialized value may result in a useless read operation, but only very improbably. NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this function must be written such that it cannot end up waiting for these latches! NOTE 3: the calling thread must want access to the page given: this rule is set to prevent unintended read-aheads performed by ibuf routines, a situation which could result in a deadlock if the OS does not support asynchronous io.

Returns:
number of page read requests issued
Parameters:
spacein: space id
zip_sizein: compressed page size in bytes, or 0
offsetin: page number of a page; NOTE: the current thread must want access to this page (see NOTE 3 above)

Definition at line 233 of file buf0rea.cc.

References BUF_BLOCK_FILE_PAGE, BUF_BLOCK_ZIP_PAGE, buf_LRU_stat_inc_io, buf_page_get_state(), buf_page_hash_get(), buf_page_is_accessed(), buf_pool_get(), buf_pool_mutex_enter, buf_pool_mutex_exit, BUF_READ_AHEAD_AREA, BUF_READ_ANY_PAGE, BUF_READ_IBUF_PAGES_ONLY, buf_pool_struct::curr_size, page_zip_des_struct::data, ibuf_bitmap_page(), buf_pool_struct::n_pend_reads, buf_pool_stat_struct::n_ra_pages_read, os_aio_simulated_put_read_threads_to_sleep(), os_aio_simulated_wake_handler_threads(), srv_startup_is_before_trx_rollback_phase, buf_pool_struct::stat, trx_sys_hdr_page(), ut_error, ut_min(), ut_print_timestamp(), ut_ulint_cmp(), and buf_page_struct::zip.

UNIV_INTERN void buf_read_ibuf_merge_pages ( ibool  sync,
const ulint *  space_ids,
const ib_int64_t *  space_versions,
const ulint *  page_nos,
ulint  n_stored 
)

Issues read requests for pages which the ibuf module wants to read in, in order to contract the insert buffer tree. Technically, this function is like a read-ahead function. in: number of elements in the arrays

Issues read requests for pages which the ibuf module wants to read in, in order to contract the insert buffer tree. Technically, this function is like a read-ahead function.

Parameters:
syncin: TRUE if the caller wants this function to wait for the highest address page to get read in, before this function returns
space_idsin: array of space ids
space_versionsin: the spaces must have this version number (timestamp), otherwise we discard the read; we use this to cancel reads if DISCARD + IMPORT may have changed the tablespace size
page_nosin: array of page numbers to read, with the highest page number the last in the array
n_storedin: number of elements in the arrays

Definition at line 495 of file buf0rea.cc.

References buf_pool_get(), BUF_READ_ANY_PAGE, buf_pool_struct::curr_size, ibuf_merge_or_delete_for_page(), buf_pool_struct::n_pend_reads, os_aio_simulated_wake_handler_threads(), os_thread_sleep(), ut_a, and ut_ad.

UNIV_INTERN ibool buf_read_page ( ulint  space,
ulint  zip_size,
ulint  offset 
)

High-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there. Sets the io_fix flag and sets an exclusive lock on the buffer frame. The flag is cleared and the x-lock released by the i/o-handler thread.

Returns:
TRUE if page has been read in, FALSE in case of failure in: page number

High-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there. Sets the io_fix flag and sets an exclusive lock on the buffer frame. The flag is cleared and the x-lock released by the i/o-handler thread.

Returns:
TRUE if page has been read in, FALSE in case of failure
Parameters:
spacein: space id
zip_sizein: compressed page size in bytes, or 0
offsetin: page number

Definition at line 168 of file buf0rea.cc.

References buf_LRU_stat_inc_io, buf_pool_get(), BUF_READ_ANY_PAGE, srv_buf_pool_reads, and ut_print_timestamp().

UNIV_INTERN void buf_read_recv_pages ( ibool  sync,
ulint  space,
ulint  zip_size,
const ulint *  page_nos,
ulint  n_stored 
)

Issues read requests for pages which recovery wants to read in. in: number of page numbers in the array

Issues read requests for pages which recovery wants to read in.

Parameters:
syncin: TRUE if the caller wants this function to wait for the highest address page to get read in, before this function returns
spacein: space id
zip_sizein: compressed page size in bytes, or 0
page_nosin: array of page numbers to read, with the highest page number the last in the array
n_storedin: number of page numbers in the array

Definition at line 575 of file buf0rea.cc.

References buf_pool_get(), BUF_READ_ANY_PAGE, buf_pool_struct::n_pend_reads, os_aio_print_debug, os_aio_simulated_wake_handler_threads(), os_file_n_pending_preads, os_thread_sleep(), and recv_n_pool_free_frames.