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. See
http://dev.mysql.com/doc/refman/5.1/en/table-cache.html.
The FROM and LIKE clauses may be used.
The FROM
clause, if present, restricts the tables shown to those present in the
db_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 |
|---|---|
| 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 | ... +----------+---------------------------+--------+-------------+
