How to fix Query canceled in PostgreSQL

Connect to the database and check the current timeout setting:

SHOW statement_timeout;

The value is in milliseconds. A value of 0 means no timeout. Typical settings are 30000 (30 seconds) or 60000 (60 seconds). Note your current setting as you may need to adjust it.

Enable query logging to see which statement causes the timeout. Add to postgresql.conf or set at session level:

SET log_min_duration_statement = 0;  -- Log all queries
SET log_statement = 'all';          -- Log all SQL

Alternatively, query the slow query log or check application error logs for the SQL text that failed. Use EXPLAIN ANALYZE on the problematic query to understand execution time.

Use EXPLAIN ANALYZE to examine the query plan:

EXPLAIN ANALYZE SELECT * FROM large_table WHERE condition;

Look for sequential scans where indexes should be used. Add indexes to frequently searched columns:

CREATE INDEX idx_column_name ON table_name(column_name);

Rewrite queries to filter early, use JOINs instead of subqueries, and avoid full table scans on large tables.

If the query legitimately requires more time, increase the timeout. Set at database level for all new connections:

ALTER DATABASE mydatabase SET statement_timeout = '120s';

Or set per session before running the query:

SET statement_timeout = 120000;  -- 120 seconds in milliseconds
SELECT * FROM slow_query;

For application code, set timeout per connection in your driver/ORM configuration.

If timeouts occur while waiting for locks from other transactions, set lock_timeout separately:

SET lock_timeout = '5s';
SET statement_timeout = '60s';

This fails fast if a lock cannot be acquired, rather than waiting. Investigate which transaction holds the lock and consider breaking work into smaller transactions.

After optimization, re-run the query and verify it completes within the timeout:

\timing on
SELECT ...;  -- Check execution time

Monitor application logs and database metrics to confirm no new timeouts occur. For critical queries, consider using a read replica to avoid impacting production traffic.