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 exceedCOMPRESS_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
Press CTRL+C to copymysql> 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
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 theSHOW COLUMNS
statement to view additional information about the columns of this table, including data types and default values.For usage information, see Section 17.9.1.4, “Monitoring InnoDB Table Compression at Runtime” and Section 17.15.1.3, “Using the Compression Information Schema Tables”. For general information about
InnoDB
table compression, see Section 17.9, “InnoDB Table and Page Compression”.