Information Schema KEY_CACHES Table

MariaDB 5.2.0

The KEY_CACHES table was introduced in MariaDB 5.2.0

The Information Schema KEY_CACHES table shows statistics about the segmented key cache, which was introduced in MariaDB 5.2.0.

It contains the following columns:

Column NameDescription
KEY_CACHE_NAMEThe name of the key cache
SEGMENTStotal number of segments (set to NULL for regular key caches)
SEGMENT_NUMBERsegment number (set to NULL for any regular key caches and for rows containing aggregation statistics for segmented key caches)
FULL_SIZEmemory for cache buffers/auxiliary structures
BLOCK_SIZEsize of the blocks
USED_BLOCKSnumber of currently used blocks
UNUSED_BLOCKSnumber of currently unused blocks
DIRTY_BLOCKSnumber of currently dirty blocks
READ_REQUESTSnumber of read requests
READSnumber of actual reads from files into buffers
WRITE_REQUESTSnumber of write requests
WRITESnumber of actual writes from buffers into files

Example

SELECT * FROM information_schema.KEY_CACHES \G
********************** 1. row **********************
KEY_CACHE_NAME: default
SEGMENTS: NULL
SEGMENT_NUMBER: NULL
     FULL_SIZE: 134217728
    BLOCK_SIZE: 1024
   USED_BLOCKS: 36
 UNUSED_BLOCKS: 107146
  DIRTY_BLOCKS: 0
 READ_REQUESTS: 40305
         READS: 21
WRITE_REQUESTS: 19239
        WRITES: 358

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