MySQL 8.3 Release Notes
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_SIZEThe compressed page size in bytes.
-
COMPRESS_OPSThe number of times a B-tree page of size
PAGE_SIZEhas been compressed. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out. -
COMPRESS_OPS_OKThe number of times a B-tree page of size
PAGE_SIZEhas been successfully compressed. This count should never exceedCOMPRESS_OPS. -
COMPRESS_TIMEThe total time in seconds used for attempts to compress B-tree pages of size
PAGE_SIZE. -
UNCOMPRESS_OPSThe number of times a B-tree page of size
PAGE_SIZEhas 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_TIMEThe 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: 0Notes
-
Use these tables to measure the effectiveness of
InnoDBtable compression in your database. -
You must have the
PROCESSprivilege to query this table. -
Use the
INFORMATION_SCHEMACOLUMNStable or theSHOW COLUMNSstatement to view additional information about the columns of this table, including data types and default values. -
For usage information, see Section 17.9.1.4, “Monitoring InnoDB Table Compression at Runtime” and Section 17.15.1.3, “Using the Compression Information Schema Tables”. For general information about
InnoDBtable compression, see Section 17.9, “InnoDB Table and Page Compression”.