5.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table

The INNODB_BUFFER_POOL_STATS table provides much of the same buffer pool information provided in SHOW ENGINE INNODB STATUS output. Much of the same information may also be obtained using InnoDB buffer pool server status variables.

The idea of making pages in the buffer pool “young” or “not young” refers to transferring them between the sublists at the head and tail of the buffer pool data structure. Pages made “young” take longer to age out of the buffer pool, while pages made “not young” are moved much closer to the point of eviction.

For related usage information and examples, see InnoDB INFORMATION_SCHEMA Buffer Pool Tables.

The INNODB_BUFFER_POOL_STATS table has these columns:

• POOL_ID

  The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances.

• POOL_SIZE

  The InnoDB buffer pool size in pages.

• FREE_BUFFERS

  The number of free pages in the InnoDB buffer pool.

• DATABASE_PAGES

  The number of pages in the InnoDB buffer pool containing data. This number includes both dirty and clean pages.

• OLD_DATABASE_PAGES

  The number of pages in the old buffer pool sublist.

• MODIFIED_DATABASE_PAGES

  The number of modified (dirty) database pages.

• PENDING_DECOMPRESS

  The number of pages pending decompression.

• PENDING_READS

  The number of pending reads.

• PENDING_FLUSH_LRU

  The number of pages pending flush in the LRU.

• PENDING_FLUSH_LIST

  The number of pages pending flush in the flush list.

• PAGES_MADE_YOUNG

  The number of pages made young.

• PAGES_NOT_MADE_YOUNG

  The number of pages not made young.

• PAGES_MADE_YOUNG_RATE

  The number of pages made young per second (pages made young since the last printout / time elapsed).

• PAGES_MADE_NOT_YOUNG_RATE

  The number of pages not made per second (pages not made young since the last printout / time elapsed).

• NUMBER_PAGES_READ

  The number of pages read.

• NUMBER_PAGES_CREATED

  The number of pages created.

• NUMBER_PAGES_WRITTEN

  The number of pages written.

• PAGES_READ_RATE

  The number of pages read per second (pages read since the last printout / time elapsed).

• PAGES_CREATE_RATE

  The number of pages created per second (pages created since the last printout / time elapsed).

• PAGES_WRITTEN_RATE

  The number of pages written per second (pages written since the last printout / time elapsed).

• NUMBER_PAGES_GET

  The number of logical read requests.

• HIT_RATE

  The buffer pool hit rate.

• YOUNG_MAKE_PER_THOUSAND_GETS

  The number of pages made young per thousand gets.

• NOT_YOUNG_MAKE_PER_THOUSAND_GETS

  The number of pages not made young per thousand gets.

• NUMBER_PAGES_READ_AHEAD

  The number of pages read ahead.

• NUMBER_READ_AHEAD_EVICTED

  The number of pages read into the InnoDB buffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries.

• READ_AHEAD_RATE

  The read-ahead rate per second (pages read ahead since the last printout / time elapsed).

• READ_AHEAD_EVICTED_RATE

  The number of read-ahead pages evicted without access per second (read-ahead pages not accessed since the last printout / time elapsed).

• LRU_IO_TOTAL

  Total LRU I/O.

• LRU_IO_CURRENT

  LRU I/O for the current interval.

• UNCOMPRESS_TOTAL

  The total number of pages decompressed.

• UNCOMPRESS_CURRENT

  The number of pages decompressed in the current interval.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS\G
*************************** 1. row ***************************
                         POOL_ID: 0
                       POOL_SIZE: 8192
                    FREE_BUFFERS: 1
                  DATABASE_PAGES: 8085
              OLD_DATABASE_PAGES: 2964
         MODIFIED_DATABASE_PAGES: 0
              PENDING_DECOMPRESS: 0
                   PENDING_READS: 0
               PENDING_FLUSH_LRU: 0
              PENDING_FLUSH_LIST: 0
                PAGES_MADE_YOUNG: 22821
            PAGES_NOT_MADE_YOUNG: 3544303
           PAGES_MADE_YOUNG_RATE: 357.62602199870594
       PAGES_MADE_NOT_YOUNG_RATE: 0
               NUMBER_PAGES_READ: 2389
            NUMBER_PAGES_CREATED: 12385
            NUMBER_PAGES_WRITTEN: 13111
                 PAGES_READ_RATE: 0
               PAGES_CREATE_RATE: 0
              PAGES_WRITTEN_RATE: 0
                NUMBER_PAGES_GET: 33322210
                        HIT_RATE: 1000
    YOUNG_MAKE_PER_THOUSAND_GETS: 18
NOT_YOUNG_MAKE_PER_THOUSAND_GETS: 0
         NUMBER_PAGES_READ_AHEAD: 2024
       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

Notes

• This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

• You must have the PROCESS privilege to query this table.

• Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.