Enable PostgreSQL query logging

To record SQL statements, set log_statement to the category you need. To have PostgreSQL itself manage log files, enable logging_collector. These are separate decisions: statements can also go to stderr, a service journal, or syslog without PostgreSQL's file collector.

Write statement logs to managed files

An example postgresql.conf:

log_destination = 'stderr'
logging_collector = on
log_directory = 'pg_log'
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_statement = 'all'

Here, pg_log is an explicitly chosen directory relative to data_directory, not a universal default. Ask the server for its active paths:

SHOW config_file;
SHOW data_directory;
SHOW log_directory;

Enabling or disabling logging_collector requires restarting the correct database instance. On a systemd installation, that might be:

sudo systemctl restart postgresql

Distribution packages can use a versioned or cluster-specific unit instead. Identify it before restarting; the generic unit may be only an umbrella service.

Change statement logging without a restart

For a privileged, persistent instance-level setting:

ALTER SYSTEM SET log_statement = 'all';
SELECT pg_reload_conf();

ALTER SYSTEM writes a persistent setting. It is not automatically temporary. Record the previous value and restore it after the investigation. If you added a new override and want to remove it:

ALTER SYSTEM RESET log_statement;
SELECT pg_reload_conf();

Resetting exposes any value in another configuration source, so check the effective result with SHOW log_statement.

Pick the appropriate category

Other error and duration settings can still log SQL when log_statement is none. Conversely, all does not guarantee every malformed SQL string appears: logging occurs after basic parsing.

Prefer a bounded performance investigation

log_min_duration_statement = 500

This records completed statements taking at least 500 ms. Threshold units are milliseconds, and 0 records all completed statement durations. Keep enough process or session context to link separate entries.

Full statement logging can generate considerable I/O and sensitive data. Once the path is confirmed, DataKit file collection can centralize it. Test multiline boundaries and timestamps using a fresh sample, and review parameter exposure before ingestion.

Can I limit logging to a user? With suitable privileges, ALTER ROLE app_user SET log_statement = 'all' sets a default for that role's new sessions. Reconnect to test it and reset the role setting when finished.

Where is the file? In this example it is below data_directory/pg_log. In another deployment, inspect the destination and service redirection instead of assuming that path.

See PostgreSQL logging configuration.