These system tables provide metadata about XtraDB tables, including their storage, statistics, and other properties for advanced analysis and management.
The Information Schema CHANGED_PAGE_BITMAPS table is a dummy table added to XtraDB with reset_table callback to allow FLUSH NO_WRITE_TO_BINLOG CHANGED_PAGE_BITMAPS to be called from innobackupex. It contains only one column, dummy.
For more information, see MDEV-7472.
The PROCESS privilege is required to view the table.
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The INNODB_UNDO_LOGS are a Percona enhancement, introduced in version MariaDB 5.5.27 and removed in 10.0.
The Information Schema INNODB_UNDO_LOGS table is a Percona enchancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains information about the InnoDB undo log, with each record being an undo log segment. It was removed in MariaDB 10.0.
It has the following columns:
TRX_ID
Unique transaction ID number, matching the value from the information_schema.INNODB_TRX table.
RSEG_ID
Rollback segment ID, matching the value from the information_schema.INNODB_RSEG table.
USEG_ID
Undo segment ID.
SEGMENT_TYPE
Indicates the operation type, for example INSERT or UPDATE.
STATE
Segment state; one of ACTIVE (contains active transaction undo log), CACHED, TO_FREE (insert undo segment can be freed), TO_PURGE (update undo segment won't be re-used and can be purged when all undo data is removed) or PREPARED (segment of a prepared transaction).
SIZE
Size in pages of the segment.
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The Information Schema XTRADB_INTERNAL_HASH_TABLES table contains InnoDB/XtraDB hash table memory usage information.
The PROCESS privilege is required to view the table.
It has the following columns:
INTERNAL_HASH_TABLE_NAME
Hash table name
TOTAL_MEMORY
Total memory
CONSTANT_MEMORY
Constant memory
VARIABLE_MEMORY
Variable memory
SELECT * FROM information_schema.XTRADB_INTERNAL_HASH_TABLES;
+--------------------------------+--------------+-----------------+-----------------+
| INTERNAL_HASH_TABLE_NAME | TOTAL_MEMORY | CONSTANT_MEMORY | VARIABLE_MEMORY |
+--------------------------------+--------------+-----------------+-----------------+
| Adaptive hash index | 2217568 | 2213368 | 4200 |
| Page hash (buffer pool 0 only) | 139112 | 139112 | 0 |
| Dictionary Cache | 613423 | 554768 | 58655 |
| File system | 816368 | 812272 | 4096 |
| Lock System | 332872 | 332872 | 0 |
| Recovery System | 0 | 0 | 0 |
+--------------------------------+--------------+-----------------+-----------------+This page is licensed: CC BY-SA / Gnu FDL
The Information Schema XTRADB_READ_VIEW table contains information about the oldest active transaction in the system.
The PROCESS privilege is required to view the table.
It has the following columns:
READ_VIEW_UNDO_NUMBER
READ_VIEW_LOW_LIMIT_TRX_NUMBER
Highest transaction number at the time the view was created.
READ_VIEW_UPPER_LIMIT_TRX_ID
Highest transaction ID at the time the view was created. Should not see newer transactions with IDs equal to or greater than the value.
READ_VIEW_LOW_LIMIT_TRX_ID
Latest committed transaction ID at the time the oldest view was created. Should see all transactions with IDs equal to or less than the value.
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The Information Schema XTRADB_RSEG table contains information about the XtraDB rollback segments.
The PROCESS privilege is required to view the table.
It has the following columns:
rseg_id
Rollback segment id.
space_id
Space where the segment is placed.
zip_size
Size in bytes of the compressed page size, or zero if uncompressed.
page_no
Page number of the segment header.
max_size
Maximum size in pages.
curr_size
Current size in pages.
The number of records will match the value set in the innodb_undo_logs variable (by default 128).
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