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MySQL 9.4 Reference Manual

28.4.6 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

TheINNODB_CMP andINNODB_CMP_RESET tables provide status information on operations related tocompressedInnoDB tables.

TheINNODB_CMP andINNODB_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 sizePAGE_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 sizePAGE_SIZE has been successfully compressed. This count should never exceedCOMPRESS_OPS.
COMPRESS_TIME
The total time in seconds used for attempts to compress B-tree pages of sizePAGE_SIZE.
UNCOMPRESS_OPS
The number of times a B-tree page of sizePAGE_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 sizePAGE_SIZE.

Example

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

Notes

Use these tables to measure the effectiveness ofInnoDB tablecompression in your database.
You must have thePROCESS privilege to query this table.
Use theINFORMATION_SCHEMACOLUMNS table or theSHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.
For usage information, seeSection 17.9.1.4, “Monitoring InnoDB Table Compression at Runtime” andSection 17.15.1.3, “Using the Compression Information Schema Tables”. For general information aboutInnoDB table compression, seeSection 17.9, “InnoDB Table and Page Compression”.

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