21.29.16 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table

The INNODB_BUFFER_PAGE table holds information about each page in the InnoDB buffer pool.

Table 21.16 INNODB_BUFFER_PAGE Columns

Column nameDescription
POOL_IDBuffer Pool ID. An identifier to distinguish between multiple buffer pool instances.
BLOCK_IDBuffer Pool Block ID.
SPACETablespace ID. Uses the same value as in INNODB_SYS_TABLES.SPACE.
PAGE_NUMBERPage number.
PAGE_TYPEPage type string. One of allocated (Freshly allocated page), index (B-tree node), undo_log (Undo log page), inode (Index node), ibuf_free_list (Insert buffer free list), ibuf_bitmap (Insert buffer bitmap), system (System page), trx_system (Transaction system data), file_space_header (File space header), extent_descriptor (Extent descriptor page), blob (Uncompressed BLOB page), compressed_blob (First compressed BLOB page), compressed_blob2 (Subsequent comp BLOB page), unknown (unknown).
FLUSH_TYPEFlush type.
FIX_COUNTNumber of threads using this block within the buffer pool. When zero, the block is eligible to be evicted.
IS_HASHEDWhether hash index has been built on this page.
NEWEST_MODIFICATIONLog Sequence Number of the youngest modification.
OLDEST_MODIFICATIONLog Sequence Number of the oldest modification.
ACCESS_TIMEAn abstract number used to judge the first access time of the page.
TABLE_NAMEName of the table the page belongs to.
INDEX_NAMEName of the index the page belongs to. It can be the name of a clustered index or a secondary index.
NUMBER_RECORDSNumber of records within the page.
DATA_SIZESum of the sizes of the records.
COMPRESSED_SIZECompressed page size. Null for pages that are not compressed.
PAGE_STATEPage state. A page with valid data has one of the following states: FILE_PAGE (buffers a page of data from a file), MEMORY (buffers a page from an in-memory object), Other possible states (managed by InnoDB) are: null, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXSpecifies whether any I/O is pending for this page: IO_NONE = no pending I/O, IO_READ = read pending, IO_WRITE = write pending.
IS_OLDSpecifies whether or not the block is in the sublist of old blocks in the LRU list.
FREE_PAGE_CLOCKThe value of the freed_page_clock counter when the block was the last placed at the head of the LRU list. The freed_page_clock counter tracks the number of blocks removed from the end of the LRU list.

Notes: