20.28.1. The INFORMATION_SCHEMA INNODB_CMP and
INNODB_CMP_RESET Tables
The INNODB_CMP and
INNODB_CMP_RESET tables contain status
information on operations related to compressed
InnoDB tables.
Table 20.1. 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.
Notes:
Use these tables to measure the effectiveness of
InnoDB table compression in your database.
You must have the PROCESS privilege to
query this table.
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