28.4.6 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

28.4.6 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

The INNODB_CMP and INNODB_CMP_RESET tables provide status information on operations related to compressed InnoDB tables.

The INNODB_CMP and INNODB_CMP_RESET tables have these columns:

  • PAGE_SIZE

The compressed page size in bytes. - COMPRESS_OPS

The number of times a B-tree page of size PAGE_SIZE has been compressed. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out. - COMPRESS_OPS_OK

The number of times a B-tree page of size PAGE_SIZE has been successfully compressed. This count should never exceed COMPRESS_OPS. - COMPRESS_TIME

The total time in seconds used for attempts to compress B-tree pages of size PAGE_SIZE. - UNCOMPRESS_OPS

The number of times a B-tree page of size PAGE_SIZE has been uncompressed. B-tree pages are uncompressed whenever compression fails or at first access when the uncompressed page does not exist in the buffer pool. - UNCOMPRESS_TIME

The total time in seconds used for uncompressing B-tree pages of the size PAGE_SIZE.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMP\G
*************************** 1. row ***************************
      page_size: 1024
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 2. row ***************************
      page_size: 2048
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 3. row ***************************
      page_size: 4096
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 4. row ***************************
      page_size: 8192
   compress_ops: 86955
compress_ops_ok: 81182
  compress_time: 27
 uncompress_ops: 26828
uncompress_time: 5
*************************** 5. row ***************************
      page_size: 16384
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0

Notes