- 6.2 Information Schema Tables about Compression
- 6.2.1 INNODB_CMP and INNODB_CMP_RESET
- 6.2.2 INNODB_CMPMEM and INNODB_CMPMEM_RESET
- 6.2.3 Using the Compression Information Schema Tables
The tables INNODB_CMP and
INNODB_CMP_RESET contain status information
on the operations related to compressed tables, which are covered
in Chapter 3, InnoDB Data Compression. The compressed
page size is in the column PAGE_SIZE.
These two tables have identical contents, but reading from
INNODB_CMP_RESET resets the statistics on
compression and uncompression operations. For example, if you
archived the output of INNODB_CMP_RESET every
60 minutes, it would show the hourly statistics. If you never
read INNODB_CMP_RESET and monitored the
output of INNODB_CMP instead, it would show
the cumulated statistics since InnoDB was started.
Table 6.1. 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. |
This is the User’s Guide for InnoDB Plugin 1.0.6 for MySQL 5.1, generated on March 4, 2010 (rev 673:680M).
