The CANCEL QUERY
statement cancels a running SQL query.
Considerations
- Schema changes are treated differently than other SQL queries. You can use
SHOW JOBS
to monitor the progress of schema changes andCANCEL JOB
to cancel schema changes that are taking longer than expected. - In rare cases where a query is close to completion when a cancellation request is issued, the query may run to completion.
- In addition to the
CANCEL QUERY
statement, CockroachDB also supports query cancellation by client drivers and ORMs using the PostgreSQL wire protocol (pgwire). This allows CockroachDB to stop executing queries that your application is no longer waiting for, thereby reducing load on the cluster. pgwire query cancellation differs from theCANCEL QUERY
statement in the following ways:- It is how most client drivers and ORMS implement query cancellation. For example, it is used by PGJDBC to implement the
setQueryTimeout
method. - The cancellation request is sent over a different network connection than is used by SQL connections.
- If there are too many unsuccessful cancellation attempts, CockroachDB will start rejecting pgwire cancellations.
- It is how most client drivers and ORMS implement query cancellation. For example, it is used by PGJDBC to implement the
Required privileges
Members of the admin
role (including root
, which belongs to admin
by default) can cancel any currently active queries. User that are not members of the admin
role can cancel only their own currently active queries. To view and cancel another non-admin user's query, the user must be a member of the admin
role or must have the VIEWACTIVITY
system privilege (or the legacy VIEWACTIVITY
role option) and the CANCELQUERY
system privilege (or the legacy CANCELQUERY
role option) defined.
Synopsis
Parameters
Parameter | Description |
---|---|
query_id |
A scalar expression that produces the ID of the query to cancel.CANCEL QUERY accepts a single query ID. If a subquery is used and returns multiple IDs, the CANCEL QUERY statement will fail. To cancel multiple queries, use CANCEL QUERIES . |
select_stmt |
A selection query whose result you want to cancel. |
Response
When a query is successfully cancelled, CockroachDB sends a query execution canceled
error to the client that issued the query.
- If the canceled query was a single, stand-alone statement, no further action is required by the client.
- If the canceled query was part of a larger, multi-statement transaction, the client should then issue a
ROLLBACK
statement.
Examples
Cancel a query via the query ID
In this example, we use the SHOW STATEMENTS
statement to get the ID of a query and then pass the ID into the CANCEL QUERY
statement:
> SHOW STATEMENTS;
query_id | node_id | session_id | user_name | start | query | client_address | application_name | distributed | phase
-----------------------------------+---------+----------------------------------+-----------+-------------------------------------+--------------------------------------+-----------------+------------------+-------------+------------
1673f58fca5301900000000000000001 | 1 | 1673f583067d51280000000000000001 | demo | 2021-04-08 18:31:29.079614+00:00:00 | SELECT * FROM rides ORDER BY revenue | 127.0.0.1:55212 | $ cockroach demo | true | executing
1673f590433eaa000000000000000001 | 1 | 1673f58a4ba3c8e80000000000000001 | demo | 2021-04-08 18:31:31.108372+00:00:00 | SHOW CLUSTER STATEMENTS | 127.0.0.1:55215 | $ cockroach sql | false | executing
(2 rows)
> CANCEL QUERY '1673f590433eaa000000000000000001';
Cancel a query via a subquery
In this example, we nest a SELECT
clause that retrieves the ID of a query inside the CANCEL QUERY
statement:
> CANCEL QUERY (WITH x AS (SHOW CLUSTER STATEMENTS) SELECT query_id FROM x
WHERE client_address = '127.0.0.1:55212'
AND user_name = 'demo'
AND query = 'SELECT * FROM rides ORDER BY revenue');
CANCEL QUERIES 1
CANCEL QUERY
accepts a single query ID. If a subquery is used and returns multiple IDs, the CANCEL QUERY
statement will fail. To cancel multiple queries, use CANCEL QUERIES
.