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25.39.5 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

Contents

The INNODB_CMP and INNODB_CMP_RESET tables provide status information on operations related to compressed InnoDB tables.

The INNODB_CMP and INNODB_CMP_RESET tables have these columns:

PAGE_SIZE
The compressed page size in bytes.
COMPRESS_OPS
The number of times a B-tree page of 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
The number of times a B-tree page of size PAGE_SIZE has been successfully compressed. This count should never exceed COMPRESS_OPS.
COMPRESS_TIME
The total time in seconds used for attempts to compress B-tree pages of size PAGE_SIZE.
UNCOMPRESS_OPS
The number of times a B-tree page of 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
The total time in seconds used for uncompressing B-tree pages of the size PAGE_SIZE.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMP\G
*************************** 1. row ***************************
page_size: 1024
compress_ops: 0
compress_ops_ok: 0
compress_time: 0
uncompress_ops: 0
uncompress_time: 0
*************************** 2. row ***************************
page_size: 2048
compress_ops: 0
compress_ops_ok: 0
compress_time: 0
uncompress_ops: 0
uncompress_time: 0
*************************** 3. row ***************************
page_size: 4096
compress_ops: 0
compress_ops_ok: 0
compress_time: 0
uncompress_ops: 0
uncompress_time: 0
*************************** 4. row ***************************
page_size: 8192
compress_ops: 86955
compress_ops_ok: 81182
compress_time: 27
uncompress_ops: 26828
uncompress_time: 5
*************************** 5. row ***************************
page_size: 16384
compress_ops: 0
compress_ops_ok: 0
compress_time: 0
uncompress_ops: 0
uncompress_time: 0

Contents Haut

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.
Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.
For usage information, see Section 15.9.1.4, “Monitoring InnoDB Table Compression at Runtime” and Section 15.14.1.3, “Using the Compression Information Schema Tables”. For general information about InnoDB table compression, see Section 15.9, “InnoDB Table and Page Compression”.

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