Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables contain status information on operations related to
compressed 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 index.
Table 20.2. Columns of INNODB_CMP_PER_INDEX andINNODB_CMP_PER_INDEX_RESET
| Column name | Description |
|---|---|
DATABASE_NAME |
Database containing the applicable table. |
TABLE_NAME |
Table to monitor for compression statistics. |
INDEX_NAME |
Index to monitor for compression statistics. |
COMPRESS_OPS |
Number of compression operations attempted. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out. |
COMPRESS_OPS_OK |
Number of successful compression operations. Subtract from the COMPRESS_OPS
value to get the number of compression failures. Divide by
the COMPRESS_OPS value to get the percentage of compression
failures.
|
COMPRESS_TIME |
Total amount of CPU time, in seconds, used for compressing data in this index. |
UNCOMPRESS_OPS |
Number of uncompression operations performed. Compressed InnoDB
pages are uncompressed whenever compression fails, or the
first time a compressed page is accessed in the buffer pool and the
uncompressed page does not exist.
|
UNCOMPRESS_TIME |
Total amount of CPU time, in seconds, used for uncompressing data inthis index. |
Notes:
Use these tables to measure the effectiveness of InnoDB table compression for 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 innodb_cmp_per_index_enabled configuration option before performing
the operations on compressed tables that you want to monitor.
For usage information, see Section
5.4.6.4, "Monitoring Compression at Runtime" and Section
14.2.4.3.1.3, "Using the Compression Information Schema Tables". For general information about InnoDB table compression, see Section
5.4.6, "Working with InnoDB Compressed Tables".