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MySQL 9.1.0
Source Code Documentation
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MySQL 9.1.0
Source Code Documentation
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The database buffer read. More...
Go to the source code of this file.
Functions | |
| ulint | buf_read_page_low (dberr_t *err, bool sync, ulint type, ulint mode, const page_id_t &page_id, const page_size_t &page_size, bool unzip) |
| Low-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there, in which case does nothing. More... | |
| bool | buf_read_page (const page_id_t &page_id, const page_size_t &page_size) |
| High-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there. More... | |
| bool | buf_read_page_background (const page_id_t &page_id, const page_size_t &page_size, bool sync) |
| High-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there. More... | |
| ulint | buf_read_ahead_random (const page_id_t &page_id, const page_size_t &page_size, bool inside_ibuf) |
| Applies a random read-ahead in buf_pool if there are at least a threshold value of accessed pages from the random read-ahead area. More... | |
| ulint | buf_read_ahead_linear (const page_id_t &page_id, const page_size_t &page_size, bool inside_ibuf) |
| 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. More... | |
| void | buf_read_ibuf_merge_pages (bool sync, const space_id_t *space_ids, const page_no_t *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. More... | |
| void | buf_read_recv_pages (space_id_t space_id, const page_no_t *page_nos, ulint n_stored) |
| Issues asynchronous read requests for pages which recovery wants to read in. More... | |
Variables | |
Modes used in read-ahead | |
| constexpr uint32_t | BUF_READ_IBUF_PAGES_ONLY = 131 |
| read only pages belonging to the insert buffer tree More... | |
| constexpr uint32_t | BUF_READ_ANY_PAGE = 132 |
| read any page More... | |
The database buffer read.
Created 11/5/1995 Heikki Tuuri
| ulint buf_read_ahead_linear | ( | const page_id_t & | page_id, |
| const page_size_t & | page_size, | ||
| bool | inside_ibuf | ||
| ) |
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 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.
| [in] | page_id | page id; see NOTE 3 above |
| [in] | page_size | page size |
| [in] | inside_ibuf | true if we are inside ibuf routine |
| ulint buf_read_ahead_random | ( | const page_id_t & | page_id, |
| const page_size_t & | page_size, | ||
| bool | inside_ibuf | ||
| ) |
Applies a random read-ahead in buf_pool if there are at least a threshold value of accessed pages from the random read-ahead area.
Does not read any page, not even the one at the position (space, offset), if the read-ahead mechanism is not activated. NOTE 1: 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 2: 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 i/o.
| [in] | page_id | page id of a page which the current thread wants to access |
| [in] | page_size | page size |
| [in] | inside_ibuf | true if we are inside ibuf routine |
| void buf_read_ibuf_merge_pages | ( | bool | sync, |
| const space_id_t * | space_ids, | ||
| const page_no_t * | 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] | sync | true if the caller wants this function to wait for the highest address page to get read in, before this function returns. |
| [in] | space_ids | Array of space ids. |
| [in] | page_nos | Array of page numbers to read, with the highest page number the last in the array. |
| [in] | n_stored | number of elements in the arrays. |
| bool buf_read_page | ( | const page_id_t & | page_id, |
| const page_size_t & | page_size | ||
| ) |
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.
| [in] | page_id | page id |
| [in] | page_size | page size |
| bool buf_read_page_background | ( | const page_id_t & | page_id, |
| const page_size_t & | page_size, | ||
| bool | sync | ||
| ) |
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.
| [in] | page_id | page id |
| [in] | page_size | page size |
| [in] | sync | true if synchronous aio is desired |
| ulint buf_read_page_low | ( | dberr_t * | err, |
| bool | sync, | ||
| ulint | type, | ||
| ulint | mode, | ||
| const page_id_t & | page_id, | ||
| const page_size_t & | page_size, | ||
| bool | unzip | ||
| ) |
Low-level function which reads a page asynchronously from a file to the buffer buf_pool if it is not already there, in which case does nothing.
Sets the io_fix flag and sets an exclusive lock on the buffer frame. The flag is cleared and the x-lock released by an i/o-handler thread.
| [out] | err | DB_SUCCESS or DB_TABLESPACE_DELETED if we are trying to read from a non-existent tablespace or a tablespace which is just now being dropped |
| [in] | sync | whether synchronous aio is desired |
| [in] | type | Request type |
| [in] | mode | BUF_READ_IBUF_PAGES_ONLY, ... |
| [in] | page_id | page id |
| [in] | page_size | page size |
| [in] | unzip | true=request uncompressed page |
| void buf_read_recv_pages | ( | space_id_t | space_id, |
| const page_no_t * | page_nos, | ||
| ulint | n_stored | ||
| ) |
Issues asynchronous read requests for pages which recovery wants to read in.
| [in] | space_id | tablespace id |
| [in] | page_nos | array of page numbers to read, with the highest page number the last in the array |
| [in] | n_stored | number of page numbers in the array |
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constexpr |
read any page
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constexpr |
read only pages belonging to the insert buffer tree
1.9.2