14.16.5 InnoDB INFORMATION_SCHEMA 缓冲池 table
InnoDB
INFORMATION_SCHEMA
缓冲池 table 提供有关InnoDB
缓冲池中页面的缓冲池状态信息和元数据。
InnoDB
INFORMATION_SCHEMA
缓冲池 table 包括以下列 table:
mysql> SHOW TABLES FROM INFORMATION_SCHEMA LIKE 'INNODB_BUFFER%';
+-----------------------------------------------+
| Tables_in_INFORMATION_SCHEMA (INNODB_BUFFER%) |
+-----------------------------------------------+
| INNODB_BUFFER_PAGE_LRU |
| INNODB_BUFFER_PAGE |
| INNODB_BUFFER_POOL_STATS |
+-----------------------------------------------+
Table Overview
-
INNODB_BUFFER_PAGE:保存有关
InnoDB
缓冲池中每个页面的信息。 -
INNODB_BUFFER_PAGE_LRU:保存有关
InnoDB
缓冲池中页面的信息,尤其是 LRU 列 table 中它们的排序方式,该列 table 确定在缓冲池已满时应从缓冲池中逐出哪些页面。 INNODB_BUFFER_PAGE_LRUtable 具有与INNODB_BUFFER_PAGEtable 相同的列,除了INNODB_BUFFER_PAGE_LRUtable 具有LRU_POSITION
列而不是BLOCK_ID
列。 -
INNODB_BUFFER_POOL_STATS:提供缓冲池状态信息。相同的大部分信息由显示引擎的 INNODB 状态输出提供,或者可以使用
InnoDB
缓冲池服务器状态变量获得。
Warning
查询INNODB_BUFFER_PAGE或INNODB_BUFFER_PAGE_LRUtable 可能会影响性能。除非您了解性能影响并确定可接受,否则不要在生产系统上查询这些 table。为避免影响生产系统的性能,请重现要调查的问题并在测试实例上查询缓冲池统计信息。
示例 14.6 在 INNODB_BUFFER_PAGEtable 中查询系统数据
此查询通过排除 table 名中 table 示TABLE_NAME
值为NULL
或斜杠/
或句点.
的页面(table 示用户定义的 table)来提供包含系统数据的页面的近似计数。
mysql> SELECT COUNT(*) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NULL OR (INSTR(TABLE_NAME, '/') = 0 AND INSTR(TABLE_NAME, '.') = 0);
+----------+
| COUNT(*) |
+----------+
| 1516 |
+----------+
该查询返回包含系统数据的页面的大约数量,缓冲池页面的总数以及包含系统数据的页面的大约百分比。
mysql> SELECT
(SELECT COUNT(*) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NULL OR (INSTR(TABLE_NAME, '/') = 0 AND INSTR(TABLE_NAME, '.') = 0)
) AS system_pages,
(
SELECT COUNT(*)
FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
) AS total_pages,
(
SELECT ROUND((system_pages/total_pages) * 100)
) AS system_page_percentage;
+--------------+-------------+------------------------+
| system_pages | total_pages | system_page_percentage |
+--------------+-------------+------------------------+
| 295 | 8192 | 4 |
+--------------+-------------+------------------------+
可以通过查询PAGE_TYPE
值来确定缓冲池中系统数据的类型。例如,以下查询返回包含系统数据的页面中的八个不同的PAGE_TYPE
值:
mysql> SELECT DISTINCT PAGE_TYPE FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NULL OR (INSTR(TABLE_NAME, '/') = 0 AND INSTR(TABLE_NAME, '.') = 0);
+-------------------+
| PAGE_TYPE |
+-------------------+
| SYSTEM |
| IBUF_BITMAP |
| UNKNOWN |
| FILE_SPACE_HEADER |
| INODE |
| UNDO_LOG |
| ALLOCATED |
+-------------------+
示例 14.7 在 INNODB_BUFFER_PAGEtable 中查询用户数据
该查询通过对TABLE_NAME
值为NOT NULL
和NOT LIKE '%INNODB_SYS_TABLES%'
的页面进行计数来提供包含用户数据的页面的近似计数。
mysql> SELECT COUNT(*) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NOT NULL AND TABLE_NAME NOT LIKE '%INNODB_SYS_TABLES%';
+----------+
| COUNT(*) |
+----------+
| 7897 |
+----------+
该查询返回包含用户数据的页面的大约数量,缓冲池页面的总数以及包含用户数据的页面的大约百分比。
mysql> SELECT
(SELECT COUNT(*) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NOT NULL AND (INSTR(TABLE_NAME, '/') > 0 OR INSTR(TABLE_NAME, '.') > 0)
) AS user_pages,
(
SELECT COUNT(*)
FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
) AS total_pages,
(
SELECT ROUND((user_pages/total_pages) * 100)
) AS user_page_percentage;
+------------+-------------+----------------------+
| user_pages | total_pages | user_page_percentage |
+------------+-------------+----------------------+
| 7897 | 8192 | 96 |
+------------+-------------+----------------------+
此查询使用缓冲池中的页面标识用户定义的 table:
mysql> SELECT DISTINCT TABLE_NAME FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME IS NOT NULL AND (INSTR(TABLE_NAME, '/') > 0 OR INSTR(TABLE_NAME, '.') > 0)
AND TABLE_NAME NOT LIKE '`mysql`.`innodb_%';
+-------------------------+
| TABLE_NAME |
+-------------------------+
| `employees`.`salaries` |
| `employees`.`employees` |
+-------------------------+
例 14.8 在 INNODB_BUFFER_PAGEtable 中查询索引数据
有关索引页的信息,请使用索引名称查询INDEX_NAME
列。例如,以下查询返回在employees.salaries
table 上定义的emp_no
索引的页面数和页面的总数据大小:
mysql> SELECT INDEX_NAME, COUNT(*) AS Pages,
ROUND(SUM(IF(COMPRESSED_SIZE = 0, @@GLOBAL.innodb_page_size, COMPRESSED_SIZE))/1024/1024)
AS 'Total Data (MB)'
FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE INDEX_NAME='emp_no' AND TABLE_NAME = '`employees`.`salaries`';
+------------+-------+-----------------+
| INDEX_NAME | Pages | Total Data (MB) |
+------------+-------+-----------------+
| emp_no | 1609 | 25 |
+------------+-------+-----------------+
该查询返回在employees.salaries
table 上定义的所有索引的页面数和页面的总数据大小:
mysql> SELECT INDEX_NAME, COUNT(*) AS Pages,
ROUND(SUM(IF(COMPRESSED_SIZE = 0, @@GLOBAL.innodb_page_size, COMPRESSED_SIZE))/1024/1024)
AS 'Total Data (MB)'
FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
WHERE TABLE_NAME = '`employees`.`salaries`'
GROUP BY INDEX_NAME;
+------------+-------+-----------------+
| INDEX_NAME | Pages | Total Data (MB) |
+------------+-------+-----------------+
| emp_no | 1608 | 25 |
| PRIMARY | 6086 | 95 |
+------------+-------+-----------------+
示例 14.9 在 INNODB_BUFFER_PAGE_LRUtable 中查询 LRU_POSITION 数据
INNODB_BUFFER_PAGE_LRUtable 保存有关InnoDB
缓冲池中的页面的信息,尤其是它们的排序方式,以确定在缓冲池已满时要从缓冲池中逐出哪些页面。该页面的定义与INNODB_BUFFER_PAGE相同,不同之处在于该 table 具有LRU_POSITION
列而不是BLOCK_ID
列。
此查询计算employees.employees
table 的页面在 LRU 列 table 中特定位置的位置数。
mysql> SELECT COUNT(LRU_POSITION) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU
WHERE TABLE_NAME='`employees`.`employees`' AND LRU_POSITION < 3072;
+---------------------+
| COUNT(LRU_POSITION) |
+---------------------+
| 548 |
+---------------------+
例 14.10 查询 INNODB_BUFFER_POOL_STATStable
INNODB_BUFFER_POOL_STATStable 提供的信息类似于显示引擎的 INNODB 状态和InnoDB
缓冲池状态变量。
mysql> SELECT * FROM information_schema.INNODB_BUFFER_POOL_STATS \G
*************************** 1. row ***************************
POOL_ID: 0
POOL_SIZE: 8192
FREE_BUFFERS: 1
DATABASE_PAGES: 8173
OLD_DATABASE_PAGES: 3014
MODIFIED_DATABASE_PAGES: 0
PENDING_DECOMPRESS: 0
PENDING_READS: 0
PENDING_FLUSH_LRU: 0
PENDING_FLUSH_LIST: 0
PAGES_MADE_YOUNG: 15907
PAGES_NOT_MADE_YOUNG: 3803101
PAGES_MADE_YOUNG_RATE: 0
PAGES_MADE_NOT_YOUNG_RATE: 0
NUMBER_PAGES_READ: 3270
NUMBER_PAGES_CREATED: 13176
NUMBER_PAGES_WRITTEN: 15109
PAGES_READ_RATE: 0
PAGES_CREATE_RATE: 0
PAGES_WRITTEN_RATE: 0
NUMBER_PAGES_GET: 33069332
HIT_RATE: 0
YOUNG_MAKE_PER_THOUSAND_GETS: 0
NOT_YOUNG_MAKE_PER_THOUSAND_GETS: 0
NUMBER_PAGES_READ_AHEAD: 2713
NUMBER_READ_AHEAD_EVICTED: 0
READ_AHEAD_RATE: 0
READ_AHEAD_EVICTED_RATE: 0
LRU_IO_TOTAL: 0
LRU_IO_CURRENT: 0
UNCOMPRESS_TOTAL: 0
UNCOMPRESS_CURRENT: 0
为了进行比较,下面基于相同的数据集显示了显示引擎的 INNODB 状态输出和InnoDB
缓冲池状态变量输出。
有关显示引擎的 INNODB 状态输出的更多信息,请参见第 14.18.3 节“ InnoDB 标准监视器和锁定监视器输出”。
mysql> SHOW ENGINE INNODB STATUS \G
...
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 137428992
Dictionary memory allocated 579084
Buffer pool size 8192
Free buffers 1
Database pages 8173
Old database pages 3014
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 15907, not young 3803101
0.00 youngs/s, 0.00 non-youngs/s
Pages read 3270, created 13176, written 15109
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 8173, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
...
有关状态变量的说明,请参见第 5.1.9 节“服务器状态变量”。
mysql> SHOW STATUS LIKE 'Innodb_buffer%';
+---------------------------------------+-------------+
| Variable_name | Value |
+---------------------------------------+-------------+
| Innodb_buffer_pool_dump_status | not started |
| Innodb_buffer_pool_load_status | not started |
| Innodb_buffer_pool_resize_status | not started |
| Innodb_buffer_pool_pages_data | 8173 |
| Innodb_buffer_pool_bytes_data | 133906432 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 15109 |
| Innodb_buffer_pool_pages_free | 1 |
| Innodb_buffer_pool_pages_misc | 18 |
| Innodb_buffer_pool_pages_total | 8192 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 2713 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 33069332 |
| Innodb_buffer_pool_reads | 558 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 11985961 |
+---------------------------------------+-------------+