MySQL :: MySQL 8.4 Reference Manual :: 17.15.5 InnoDB INFORMATION

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17.15.5 InnoDB INFORMATION_SCHEMA 缓冲池表

InnoDB INFORMATION_SCHEMA 缓冲池表提供缓冲池状态信息和关于 InnoDB 缓冲池中页面的元数据。

InnoDB INFORMATION_SCHEMA 缓冲池表包括以下列表：

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                      |
+-----------------------------------------------+

INNODB_BUFFER_PAGE: 持有 InnoDB 缓冲池中每个页面的信息。
INNODB_BUFFER_PAGE_LRU:存储关于InnoDB缓冲池中的页面信息，特别是它们在LRU列表中排序的方式，该列表确定当缓冲池满时要从缓冲池中驱逐哪些页面。表INNODB_BUFFER_PAGE_LRU的列与表INNODB_BUFFER_PAGE相同，except that the INNODB_BUFFER_PAGE_LRU table has an LRU_POSITION column instead of a BLOCK_ID column.
INNODB_BUFFER_POOL_STATS:提供缓冲池状态信息。许多相同的信息也可以通过SHOW ENGINE INNODB STATUS输出或使用InnoDB缓冲池服务器状态变量来获取。

Warning

查询INNODB_BUFFER_PAGE或INNODB_BUFFER_PAGE_LRU表可能会影响性能。除非您了解性能影响并确定其可接受，否则不要在生产系统上查询这些表。为了避免在生产系统上影响性能，可以在测试实例中复制问题，然后在该实例上查询缓冲池统计信息。

17.6 INNODB_BUFFER_PAGE 表中的系统数据查询示例

这条查询提供了一个近似计数，用于排除包含表名为NULL、包含斜杠/或点.的页面，这些页面可能包含用户定义的表。

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 |
+----------+

这条查询返回了包含系统数据的页面数量、缓冲池中的总页数和近似百分比，用于计算包含系统数据的页面数量。

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 |
+--------------+-------------+------------------------+

缓冲池中的系统数据类型可以通过查询PAGE_TYPE值来确定。例如，以下查询返回了包含系统数据的页面中八种不同的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         |
+-------------------+

17.7 INNODB_BUFFER_PAGE 表中的用户数据查询示例

该查询提供了近似用户数据所在页面的计数，通过计算TABLE_NAME值为NOT NULL且不包含'%INNODB_TABLES%''的页面。

mysql> SELECT COUNT(*) FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE
       WHERE TABLE_NAME IS NOT NULL AND TABLE_NAME NOT LIKE '%INNODB_TABLES%';
+----------+
| COUNT(*) |
+----------+
|     7897 |
+----------+

该查询返回包含用户数据的页面数量、总缓冲池页面数量和近似包含用户数据的页面百分比。

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 |
+------------+-------------+----------------------+

该查询识别了缓冲池中用户定义表的页面：

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` |
+-------------------------+

示例17.8 INNODB_BUFFER_PAGE 表中的索引数据查询

要获取索引页面信息，请使用INDEX_NAME列，并使用索引名称。例如，以下查询返回了在employees.salaries表上定义的emp_no索引的页面数量和总数据大小：

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 |
+------------+-------+-----------------+

该查询返回了在employees.salaries表上定义的所有索引的页面数量和总数据大小：

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17.9 INNODB_BUFFER_PAGE_LRU 表中的LRU_POSITION 数据查询

INNODB_ BUFFER_PAGE_LRU 表中存储了 InnoDB 缓冲池中的页面信息，特别是它们的顺序如何确定何时从缓冲池中驱逐页面以避免缓冲池满。该表的定义与INNODB_BUFFER_PAGE 表相同，只是这个表中有一个LRU_POSITION 列，而不是一个BLOCK_ID 列。

这个查询统计了在 LRU 列表中特定位置上被 employees.employees 表的页面占用的数量。

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 |
+---------------------+

示例 17.10 INNODB_ BUFFER_POOL_STATS 表查询

INNODB_BUFFER_POOL_STATS 表提供了类似于SHOW ENGINE INNODB STATUS 和 InnoDB 缓冲池状态变量的信息。

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

为了比较，以下显示了基于同一数据集的SHOW ENGINE INNODB STATUS 输出和 InnoDB 缓冲池状态变量输出。

关于SHOW ENGINE INNODB STATUS输出的更多信息，请见第17.17.3节，“InnoDB标准监控器和锁定监控器输出”。

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]
...

关于状态变量描述，请见第7.1.10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    |
+---------------------------------------+-------------+

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