/***************************************************************************** Copyright (c) 1995, 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA *****************************************************************************/ /**************************************************//** @file include/buf0rea.h The database buffer read Created 11/5/1995 Heikki Tuuri *******************************************************/ #ifndef buf0rea_h #define buf0rea_h #include "univ.i" #include "buf0types.h" /********************************************************************//** 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. Does a random read-ahead if it seems sensible. @return number of page read requests issued: this can be greater than 1 if read-ahead occurred */ UNIV_INTERN ulint buf_read_page( /*==========*/ ulint space, /*!< in: space id */ ulint zip_size,/*!< in: compressed page size in bytes, or 0 */ ulint offset);/*!< in: page number */ /********************************************************************//** 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. @return number of page read requests issued */ UNIV_INTERN ulint buf_read_ahead_linear( /*==================*/ ulint space, /*!< in: space id */ ulint zip_size,/*!< in: compressed page size in bytes, or 0 */ ulint offset);/*!< in: page number of a page; NOTE: the current thread must want access to this page (see NOTE 3 above) */ /********************************************************************//** 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. */ UNIV_INTERN void buf_read_ibuf_merge_pages( /*======================*/ ibool sync, /*!< in: TRUE if the caller wants this function to wait for the highest address page to get read in, before this function returns */ const ulint* space_ids, /*!< in: array of space ids */ const ib_int64_t* space_versions,/*!< in: 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 */ const ulint* page_nos, /*!< in: array of page numbers to read, with the highest page number the last in the array */ ulint n_stored); /*!< in: number of elements in the arrays */ /********************************************************************//** Issues read requests for pages which recovery wants to read in. */ UNIV_INTERN void buf_read_recv_pages( /*================*/ ibool sync, /*!< in: TRUE if the caller wants this function to wait for the highest address page to get read in, before this function returns */ ulint space, /*!< in: space id */ ulint zip_size, /*!< in: compressed page size in bytes, or 0 */ const ulint* page_nos, /*!< in: array of page numbers to read, with the highest page number the last in the array */ ulint n_stored); /*!< in: number of page numbers in the array */ /** The size in pages of the area which the read-ahead algorithms read if invoked */ #define BUF_READ_AHEAD_AREA \ ut_min(64, ut_2_power_up(buf_pool->curr_size / 32)) /** @name Modes used in read-ahead @{ */ /** read only pages belonging to the insert buffer tree */ #define BUF_READ_IBUF_PAGES_ONLY 131 /** read any page */ #define BUF_READ_ANY_PAGE 132 /* @} */ #endif