SHOW OPEN TABLES

Syntax

SHOW OPEN TABLES [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW OPEN TABLES lists the non-TEMPORARY tables that are currently open in the table cache. Seetable-cache.html.

The FROM and LIKE clauses may be used.

The FROM clause, if present, restricts the tables shown to those present in thedb_name database.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The following information is returned:

Column	Description
Column	Description
Database	Database name.
Name	Table name.
In_use	Number of table instances being used.
Name_locked	1 if the table is name-locked, e.g. if it is being dropped or renamed, otherwise 0.

Before MariaDB 5.5, each use of, for example, LOCK TABLE ... WRITE would increment In_use for that table. With the implementation of the metadata locking improvements in MariaDB 5.5, LOCK TABLE... WRITE acquires a strong MDL lock, and concurrent connections will wait on this MDL lock, so any subsequent LOCK TABLE... WRITE will not increment In_use.

Example

SHOW OPEN TABLES;
+----------+---------------------------+--------+-------------+
| Database | Table                     | In_use | Name_locked |
+----------+---------------------------+--------+-------------+
...
| test     | xjson                     |      0 |           0 |
| test     | jauthor                   |      0 |           0 |
| test     | locks                     |      1 |           0 |
...
+----------+---------------------------+--------+-------------+

_{This page is licensed: GPLv2, originally from fill_help_tables.sql}