28.4.28 The INFORMATION_SCHEMA INNODB_TRX Table

The INNODB_TRX table provides information about every transaction currently executing inside InnoDB, including whether the transaction is waiting for a lock, when the transaction started, and the SQL statement the transaction is executing, if any.

For usage information, see Section 17.15.2.1, “Using InnoDB Transaction and Locking Information”.

The INNODB_TRX table has these columns:

• TRX_ID

  A unique transaction ID number, internal to InnoDB. These IDs are not created for transactions that are read only and nonlocking. For details, see Section 10.5.3, “Optimizing InnoDB Read-Only Transactions”.

• TRX_WEIGHT

  The weight of a transaction, reflecting (but not necessarily the exact count of) the number of rows altered and the number of rows locked by the transaction. To resolve a deadlock, InnoDB selects the transaction with the smallest weight as the “victim” to roll back. Transactions that have changed nontransactional tables are considered heavier than others, regardless of the number of altered and locked rows.

• TRX_STATE

  The transaction execution state. Permitted values are RUNNING, LOCK WAIT, ROLLING BACK, and COMMITTING.

• TRX_STARTED

  The transaction start time.

• TRX_REQUESTED_LOCK_ID

  The ID of the lock the transaction is currently waiting for, if TRX_STATE is LOCK WAIT; otherwise NULL. To obtain details about the lock, join this column with the ENGINE_LOCK_ID column of the Performance Schema data_locks table.

• TRX_WAIT_STARTED

  The time when the transaction started waiting on the lock, if TRX_STATE is LOCK WAIT; otherwise NULL.

• TRX_MYSQL_THREAD_ID

  The MySQL thread ID. To obtain details about the thread, join this column with the ID column of the INFORMATION_SCHEMA PROCESSLIST table, but see Section 17.15.2.3, “Persistence and Consistency of InnoDB Transaction and Locking Information”.

• TRX_QUERY

  The SQL statement that is being executed by the transaction.

• TRX_OPERATION_STATE

  The transaction's current operation, if any; otherwise NULL.

• TRX_TABLES_IN_USE

  The number of InnoDB tables used while processing the current SQL statement of this transaction.

• TRX_TABLES_LOCKED

  The number of InnoDB tables that the current SQL statement has row locks on. (Because these are row locks, not table locks, the tables can usually still be read from and written to by multiple transactions, despite some rows being locked.)

• TRX_LOCK_STRUCTS

  The number of locks reserved by the transaction.

• TRX_LOCK_MEMORY_BYTES

  The total size taken up by the lock structures of this transaction in memory.

• TRX_ROWS_LOCKED

  The approximate number or rows locked by this transaction. The value might include delete-marked rows that are physically present but not visible to the transaction.

• TRX_ROWS_MODIFIED

  The number of modified and inserted rows in this transaction.

• TRX_CONCURRENCY_TICKETS

  A value indicating how much work the current transaction can do before being swapped out, as specified by the innodb_concurrency_tickets system variable.

• TRX_ISOLATION_LEVEL

  The isolation level of the current transaction.

• TRX_UNIQUE_CHECKS

  Whether unique checks are turned on or off for the current transaction. For example, they might be turned off during a bulk data load.

• TRX_FOREIGN_KEY_CHECKS

  Whether foreign key checks are turned on or off for the current transaction. For example, they might be turned off during a bulk data load.

• TRX_LAST_FOREIGN_KEY_ERROR

  The detailed error message for the last foreign key error, if any; otherwise NULL.

• TRX_ADAPTIVE_HASH_LATCHED

  Whether the adaptive hash index is locked by the current transaction. When the adaptive hash index search system is partitioned, a single transaction does not lock the entire adaptive hash index. Adaptive hash index partitioning is controlled by innodb_adaptive_hash_index_parts, which is set to 8 by default.

• TRX_ADAPTIVE_HASH_TIMEOUT

  Deprecated in MySQL 5.7.8. Always returns 0.

  Whether to relinquish the search latch immediately for the adaptive hash index, or reserve it across calls from MySQL. When there is no adaptive hash index contention, this value remains zero and statements reserve the latch until they finish. During times of contention, it counts down to zero, and statements release the latch immediately after each row lookup. When the adaptive hash index search system is partitioned (controlled by innodb_adaptive_hash_index_parts), the value remains 0.

• TRX_IS_READ_ONLY

  A value of 1 indicates the transaction is read only.

• TRX_AUTOCOMMIT_NON_LOCKING

  A value of 1 indicates the transaction is a SELECT statement that does not use the FOR UPDATE or LOCK IN SHARED MODE clauses, and is executing with autocommit enabled so that the transaction contains only this one statement. When this column and TRX_IS_READ_ONLY are both 1, InnoDB optimizes the transaction to reduce the overhead associated with transactions that change table data.

• TRX_SCHEDULE_WEIGHT

  The transaction schedule weight assigned by the Contention-Aware Transaction Scheduling (CATS) algorithm to transactions waiting for a lock. The value is relative to the values of other transactions. A higher value has a greater weight. A value is computed only for transactions in a LOCK WAIT state, as reported by the TRX_STATE column. A NULL value is reported for transactions that are not waiting for a lock. The TRX_SCHEDULE_WEIGHT value is different from the TRX_WEIGHT value, which is computed by a different algorithm for a different purpose.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TRX\G
*************************** 1. row ***************************
                    trx_id: 1510
                 trx_state: RUNNING
               trx_started: 2014-11-19 13:24:40
     trx_requested_lock_id: NULL
          trx_wait_started: NULL
                trx_weight: 586739
       trx_mysql_thread_id: 2
                 trx_query: DELETE FROM employees.salaries WHERE salary > 65000
       trx_operation_state: updating or deleting
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 3003
     trx_lock_memory_bytes: 450768
           trx_rows_locked: 1407513
         trx_rows_modified: 583736
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
 trx_adaptive_hash_latched: 0
 trx_adaptive_hash_timeout: 10000
          trx_is_read_only: 0
trx_autocommit_non_locking: 0
       trx_schedule_weight: NULL

Notes

• Use this table to help diagnose performance problems that occur during times of heavy concurrent load. Its contents are updated as described in Section 17.15.2.3, “Persistence and Consistency of InnoDB Transaction and Locking Information”.

• You must have the PROCESS privilege to query this table.

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