INNODB_CMP_PER_INDEX_RESET tables contain
status information on operations related to
InnoDB tables and indexes, with separate
statistics for each combination of database, table, and index, to
help you evaluate the performance and usefulness of compression
for specific tables.
For a compressed
InnoDB table, both the table
data and all the secondary
indexes are compressed. In this context, the table data is
treated as just another index, one that happens to contain all the
columns: the clustered
Table 21.2 Columns of INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET
|Database containing the applicable table.|
|Table to monitor for compression statistics.|
|Index to monitor for compression statistics.|
|Number of compression operations attempted. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out.|
|Number of successful compression operations. Subtract from the
|Total amount of CPU time, in seconds, used for compressing data in this index.|
|Number of uncompression operations performed. Compressed
|Total amount of CPU time, in seconds, used for uncompressing data in this index.|
Use these tables to measure the effectiveness of
specific tables, indexes, or both.
You must have the
PROCESS privilege to
query these tables.
Because collecting separate measurements for every index
imposes substantial performance overhead, enable the
configuration option before performing the operations on
compressed tables that you want to monitor.
For usage information, see
Section 14.7.4, “Monitoring Compression at Runtime” and
Section 220.127.116.11, “Using the Compression Information Schema Tables”.
For general information about
compression, see Section 14.7, “InnoDB Compressed Tables”.