Information Schema INNODB_BUFFER_PAGE_LRU Table

The Information Schema INNODB_BUFFER_PAGE_LRU table details pages in the buffer pool and their position in the LRU eviction list.

The Information Schema INNODB_BUFFER_PAGE_LRU table contains information about pages in the buffer pool and how they are ordered for eviction purposes.

The PROCESS privilege is required to view the table.

It has the following columns:

Column	Description
POOL_ID	Buffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
LRU_POSITION	LRU (Least recently-used), for determining eviction order from the buffer pool.
SPACE	Tablespace identifier. Matches the SPACE value on the INNODB_SYS_TABLES table.
PAGE_NUMBER	Buffer pool page number.
PAGE_TYPE	Page type; one of allocated (newly-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 compressed blob page) or unknown.
FLUSH_TYPE	Flush type. 0= FLUSH_KEEP, 1 =FLUSH_RELEASE, 2 = FLUSH_IGNORE_CHANGED, 3= FLUSH_FORCE_WRITE
FIX_COUNT	Count of the threads using this block in the buffer pool. When it is zero, the block can be evicted from the buffer pool.
IS_HASHED	Whether or not a hash index has been built on this page.
NEWEST_MODIFICATION	Most recent modification's Log Sequence Number.
OLDEST_MODIFICATION	Oldest modification's Log Sequence Number.
ACCESS_TIME	Abstract number representing the time the page was first accessed.
TABLE_NAME	Table that the page belongs to.
INDEX_NAME	Index that the page belongs to, either a clustered index or a secondary index.
NUMBER_RECORDS	Number of records the page contains.
DATA_SIZE	Size in bytes of all the records contained in the page.
COMPRESSED_SIZE	Compressed size in bytes of the page, or NULL for pages that aren't compressed.
PAGE_STATE	Page state; one of FILE_PAGE (page from a file) or MEMORY (page from an in-memory object) for valid data, or one of NULL, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIX	Whether there is I/O pending for the page; one of IO_NONE (no pending I/O), IO_READ (read pending), IO_WRITE (write pending).
IS_OLD	Whether the page is old or not.
FREE_PAGE_CLOCK	Freed_page_clock counter, which tracks the number of blocks removed from the end of the LRU list, at the time the block was last placed at the head of the list.

The related INFORMATION_SCHEMA.INNODB_BUFFER_PAGE table contains the same information, but with a block id rather than LRU position.

Example

DESC information_schema.innodb_buffer_page_lru;
+---------------------+---------------------+------+-----+---------+-------+
| Field               | Type                | Null | Key | Default | Extra |
+---------------------+---------------------+------+-----+---------+-------+
| POOL_ID             | bigint(21) unsigned | NO   |     | 0       |       |
| LRU_POSITION        | bigint(21) unsigned | NO   |     | 0       |       |
| SPACE               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_NUMBER         | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_TYPE           | varchar(64)         | YES  |     | NULL    |       |
| FLUSH_TYPE          | bigint(21) unsigned | NO   |     | 0       |       |
| FIX_COUNT           | bigint(21) unsigned | NO   |     | 0       |       |
| IS_HASHED           | varchar(3)          | YES  |     | NULL    |       |
| NEWEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| OLDEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| ACCESS_TIME         | bigint(21) unsigned | NO   |     | 0       |       |
| TABLE_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| INDEX_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| NUMBER_RECORDS      | bigint(21) unsigned | NO   |     | 0       |       |
| DATA_SIZE           | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED_SIZE     | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED          | varchar(3)          | YES  |     | NULL    |       |
| IO_FIX              | varchar(64)         | YES  |     | NULL    |       |
| IS_OLD              | varchar(3)          | YES  |     | NULL    |       |
| FREE_PAGE_CLOCK     | bigint(21) unsigned | NO   |     | 0       |       |
+---------------------+---------------------+------+-----+---------+-------+

SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU\G
...
*************************** 6. row ***************************
            POOL_ID: 0
       LRU_POSITION: 5
              SPACE: 0
        PAGE_NUMBER: 11
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: NO
NEWEST_MODIFICATION: 2046835
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 2585566280
         TABLE_NAME: `SYS_INDEXES`
         INDEX_NAME: CLUST_IND
     NUMBER_RECORDS: 57
          DATA_SIZE: 4016
    COMPRESSED_SIZE: 0
         COMPRESSED: NO
             IO_FIX: IO_NONE
             IS_OLD: NO
    FREE_PAGE_CLOCK: 0
...

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