Movatterモバイル変換

Querying theINNODB_BUFFER_PAGE table can affect performance. Do not query this table on a production system unless you are aware of the performance impact and have determined it to be acceptable. To avoid impacting performance on a production system, reproduce the issue you want to investigate and query buffer pool statistics on a test instance.

• POOL_ID

  The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances.

• BLOCK_ID

  The buffer pool block ID.

• SPACE

  The tablespace ID; the same value asINNODB_TABLES.SPACE.

• PAGE_NUMBER

  The page number.

• PAGE_TYPE

  The page type. The following table shows the permitted values.

  Table 28.4 INNODB_BUFFER_PAGE.PAGE_TYPE Values

  Page Type	Description
  ALLOCATED	Freshly allocated page
  BLOB	Uncompressed BLOB page
  COMPRESSED_BLOB2	Subsequent comp BLOB page
  COMPRESSED_BLOB	First compressed BLOB page
  ENCRYPTED_RTREE	Encrypted R-tree
  EXTENT_DESCRIPTOR	Extent descriptor page
  FILE_SPACE_HEADER	File space header
  FIL_PAGE_TYPE_UNUSED	Unused
  IBUF_BITMAP	Insert buffer bitmap
  IBUF_FREE_LIST	Insert buffer free list
  IBUF_INDEX	Insert buffer index
  INDEX	B-tree node
  INODE	Index node
  LOB_DATA	Uncompressed LOB data
  LOB_FIRST	First page of uncompressed LOB
  LOB_INDEX	Uncompressed LOB index
  PAGE_IO_COMPRESSED	Compressed page
  PAGE_IO_COMPRESSED_ENCRYPTED	Compressed and encrypted page
  PAGE_IO_ENCRYPTED	Encrypted page
  RSEG_ARRAY	Rollback segment array
  RTREE_INDEX	R-tree index
  SDI_BLOB	Uncompressed SDI BLOB
  SDI_COMPRESSED_BLOB	Compressed SDI BLOB
  SDI_INDEX	SDI index
  SYSTEM	System page
  TRX_SYSTEM	Transaction system data
  UNDO_LOG	Undo log page
  UNKNOWN	Unknown
  ZLOB_DATA	Compressed LOB data
  ZLOB_FIRST	First page of compressed LOB
  ZLOB_FRAG	Compressed LOB fragment
  ZLOB_FRAG_ENTRY	Compressed LOB fragment index
  ZLOB_INDEX	Compressed LOB index

  
  

• FLUSH_TYPE

  The flush type.

• FIX_COUNT

  The number of threads using this block within the buffer pool. When zero, the block is eligible to be evicted.

• IS_HASHED

  Whether a hash index has been built on this page.

• NEWEST_MODIFICATION

  The Log Sequence Number of the youngest modification.

• OLDEST_MODIFICATION

  The Log Sequence Number of the oldest modification.

• ACCESS_TIME

  An abstract number used to judge the first access time of the page.

• TABLE_NAME

  The name of the table the page belongs to. This column is applicable only to pages with aPAGE_TYPE value ofINDEX. The column isNULL if the server has not yet accessed the table.

• INDEX_NAME

  The name of the index the page belongs to. This can be the name of a clustered index or a secondary index. This column is applicable only to pages with aPAGE_TYPE value ofINDEX.

• NUMBER_RECORDS

  The number of records within the page.

• DATA_SIZE

  The sum of the sizes of the records. This column is applicable only to pages with aPAGE_TYPE value ofINDEX.

• COMPRESSED_SIZE

  The compressed page size.NULL for pages that are not compressed.

• PAGE_STATE

  The page state. The following table shows the permitted values.

  Table 28.5 INNODB_BUFFER_PAGE.PAGE_STATE Values

  Page State	Description
  FILE_PAGE	A buffered file page
  MEMORY	Contains a main memory object
  NOT_USED	In the free list
  NULL	Clean compressed pages, compressed pages in the flush list, pages used as buffer pool watch sentinels
  READY_FOR_USE	A free page
  REMOVE_HASH	Hash index should be removed before placing in the free list

  
  

• IO_FIX

  Whether any I/O is pending for this page:IO_NONE = no pending I/O,IO_READ = read pending,IO_WRITE = write pending,IO_PIN = relocation and removal from the flush not permitted.

• IS_OLD

  Whether the block is in the sublist of old blocks in the LRU list.

• FREE_PAGE_CLOCK

  The value of thefreed_page_clock counter when the block was the last placed at the head of the LRU list. Thefreed_page_clock counter tracks the number of blocks removed from the end of the LRU list.

• IS_STALE

  Whether the page is stale.

• This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

• You must have thePROCESS privilege to query this table.

• Use theINFORMATION_SCHEMACOLUMNS table or theSHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

• When tables, table rows, partitions, or indexes are deleted, associated pages remain in the buffer pool until space is required for other data. TheINNODB_BUFFER_PAGE table reports information about these pages until they are evicted from the buffer pool. For more information about how theInnoDB manages buffer pool data, seeSection 17.5.1, “Buffer Pool”.