# RELEASE\_LOCK

## Syntax

```sql
RELEASE_LOCK(str)
```

## Description

Releases the lock named by the string `str` that was obtained with [GET\_LOCK()](/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/get_lock.md). Returns `1` if the lock was released, `0` if the lock was not established by this connection (in which case the lock is not released), and `NULL` if the named lock did not exist. The lock does not exist if it was never obtained by a call to `GET_LOCK()` or if it has previously been released.

`str` is case insensitive. If `str` is an empty string or `NULL`, `RELEASE_LOCK()` returns `NULL` and does nothing.

Statements using the `RELEASE_LOCK` function are not [safe for statement-based replication](/docs/server/ha-and-performance/standard-replication/unsafe-statements-for-statement-based-replication.md).

The [DO statement](/docs/server/reference/sql-statements/stored-routine-statements/do.md) is convenient to use with `RELEASE_LOCK()`.

## Examples

Connection1:

```sql
SELECT GET_LOCK('lock1',10);
+----------------------+
| GET_LOCK('lock1',10) |
+----------------------+
|                    1 |
+----------------------+
```

Connection 2:

```sql
SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
|                    1 |
+----------------------+
```

Connection 1:

```sql
SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'), RELEASE_LOCK('lock3');
+-----------------------+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') | RELEASE_LOCK('lock3') |
+-----------------------+-----------------------+-----------------------+
|                     1 |                     0 |                  NULL |
+-----------------------+-----------------------+-----------------------+
```

It is possible to hold the same lock recursively. This example is viewed using the [metadata\_lock\_info](/docs/server/reference/plugins/other-plugins/metadata-lock-info-plugin.md) plugin:

```sql
SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
Empty set (0.000 sec)
```

## See Also

* [GET\_LOCK](/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/get_lock.md)
* [IS\_FREE\_LOCK](/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/is_free_lock.md)
* [IS\_USED\_LOCK](/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/is_used_lock.md)
* [RELEASE\_ALL\_LOCKS](/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/release_all_locks.md)

<sub>*This page is licensed: GPLv2, originally from*</sub> [<sub>*fill\_help\_tables.sql*</sub>](https://github.com/MariaDB/server/blob/main/scripts/fill_help_tables.sql)

{% @marketo/form formId="4316" %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://mariadb.com/docs/server/reference/sql-functions/secondary-functions/miscellaneous-functions/release_lock.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.