MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
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.
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
Use these tables to measure the effectiveness of
InnoDB table
compression in your
database.
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.
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 InnoDB table
compression, see Section 17.9, “InnoDB Table and Page Compression”.