Can I log query execution time in PostgreSQL 8.4? - postgresql

Question

I want to log each query execution time which is run in a day.
For example like this,
2012-10-01 13:23:38 STATEMENT: SELECT * FROM pg_stat_database runtime:265 ms.
Please give me some guideline.

Answer 1

If you set
log_min_duration_statement = 0
log_statement = all
in your postgresql.conf, then you will see all statements being logged into the Postgres logfile.
If you enable
log_duration
that will also print the time taken for each statement. This is off by default.
Using the log_statement parameter you can control which type of statement you want to log (DDL, DML, ...)
This will produce an output like this in the logfile:
2012-10-01 13:00:43 CEST postgres LOG: statement: select count(*) from pg_class;
2012-10-01 13:00:43 CEST postgres LOG: duration: 47.000 ms
More details in the manual:
http://www.postgresql.org/docs/8.4/static/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHEN
http://www.postgresql.org/docs/8.4/static/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHAT
If you want a daily list, you probably want to configure the logfile to rotate on a daily basis. Again this is described in the manual.

Answer 2

I believe OP was actually asking for execution duration, not the timestamp.
To include the duration in the log output, open pgsql/<version>/data/postgresql.conf, find the line that reads
#log_duration = off
and change it to
log_duration = on
If you can't find the given parameter, just add it in a new line in the file.
After saving the changes, restart the postgresql service, or just invoke
pg_ctl reload -D <path to the directory of postgresql.conf>
e.g.
pg_ctl reload -D /var/lib/pgsql/9.2/data/
to reload the configuration.

Answer 3

I think a better option is to enable pg_stat_statements by enabling the PG stats extension. This will help you to find the query execution time for each query nicely recorded in a view