The INNODB_CMP and
INNODB_CMP_RESET tables contain status
information on operations related to compressed
InnoDB tables.
Table 21.4 Columns of INNODB_CMP and INNODB_CMP_RESET
| Column name | Description |
|---|---|
PAGE_SIZE | Compressed page size in bytes. |
COMPRESS_OPS | Number of times a B-tree page of the 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 | Number of times a B-tree page of the size PAGE_SIZE
has been successfully compressed. This count should never
exceed COMPRESS_OPS. |
COMPRESS_TIME | Total time in seconds spent in attempts to compress B-tree pages of the
size PAGE_SIZE. |
UNCOMPRESS_OPS | Number of times a B-tree page of the 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 | Total time in seconds spent in 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: 199755
compress_ops_ok: 112015
compress_time: 83
uncompress_ops: 74253
uncompress_time: 13
*************************** 5. row ***************************
page_size: 16384
compress_ops: 0
compress_ops_ok: 0
compress_time: 0
uncompress_ops: 0
uncompress_time: 0
Notes:
Use these tables to measure the effectiveness of
InnoDB table compression in your database.
Use DESCRIBE or
SHOW COLUMNS to view additional
information about the columns of these tables including data
types and default values.
You must have the PROCESS
privilege to query this table.
For usage information, see Section 14.18.1.3, “Using the Compression Information Schema Tables”.