The INFORMATION_SCHEMA INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables 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. The  INNODB_CMP_PER_INDEX  and  INNODB_CMP_PER_INDEX_RESET  tables have these columns: The schema (database) containing the applicable table. The table to monitor for compression statistics. The index to monitor for compression statistics. The number of compression operations attempted. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out. The 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. The total time in seconds used for compressing data in this index. The 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. The total time in seconds used for uncompressing data in this index. • DATABASE_NAME • TABLE_NAME • INDEX_NAME • COMPRESS_OPS • COMPRESS_OPS_OK • COMPRESS_TIME • UNCOMPRESS_OPS • UNCOMPRESS_TIME mysql>  SELECT * FROM INFORMATION_SCHEMA.INNODB_CMP_PER_INDEX\G *************************** 1. row *************************** database_name: employees table_name: salaries index_name: PRIMARY compress_ops: 0 compress_ops_ok: 0 compress_time: 0  uncompress_ops: 23451 uncompress_time: 4 *************************** 2. row *************************** database_name: employees Example 4856