• Update the default configuration to allow direct authentication from the local machine:

    $ sed -i 's/^local\s\+all\s\+all\s\+ident/local all all trust/g' /etc/postgresql/8.4/main/pg_hba.conf

  • Same as above but for local IPv4 and IPv6 connexions:

    $ sed -i 's/^host\s\+all\s\+all\s\+\(.*\)\s\+md5/host all all \1 trust/g' /etc/postgresql/8.4/main/pg_hba.conf

  • List databases:

    $ psql --list -U kevin

  • Create a new kevin_db database with the kevin user:

    $ createdb -U kevin kevin_db

  • Remove the database we created above:

    $ dropdb kevin_db -U kevin

  • To connect to a particular database:

    $ psql -d database_id

  • Return the result of a query by aligning its row in a single line, separated by a space (source):

    $ psql --tuples-only --no-align -d database_id -c "SELECT id FROM res_users;" | sed ':a;N;$!ba;s/\n/ /g'

  • Show us how a table of a specific database can be recreated:

    $ pg_dump my_database --schema-only --table=my_table

  • Dump a database in a compressed format:

    $ pg_dump my_database -v --format=c --file=/var/lib/postgresql/my_database-db-2011-12-19.dump

  • Restore a compressed dump:

    $ pg_restore -U my_user -d my_database /var/lib/postgresql/my_database-db-2011-12-19.dump

  • Import an SQL file to a database:

    $ psql --username kevin -d kevin_db < ./database_dump.sql

  • Search if kevin is a PostgreSQL user:

    $ sudo -u postgres psql --tuples-only --no-align --command "SELECT usename FROM pg_user;" | grep --quiet 'kevin' && echo 'User found!' || echo 'User not found!'

  • Force rebuilding of all caches of a database:

    $ psql -d db_id --command "REINDEX DATABASE db_id;"

  • Set the owner of a database:

    ALTER DATABASE db_id OWNER TO user_id;

  • Set the owner of all tables from the MY_DB_ID database to MY_DB_USER (source):

    $ for tbl in `psql -qAt -c "SELECT tablename FROM pg_tables WHERE schemaname = 'public';" MY_DB_ID` ; do psql -c "ALTER TABLE $tbl OWNER TO MY_DB_USER" MY_DB_ID ; done

  • And to run the command above as the postgres user, while fixing sequences and views too, do:

    $ su - postgres <<-'.'
    DB_NAME=testdb
    DB_USER=openerp
    for tbl in `psql -qAt -c "SELECT tablename FROM pg_tables WHERE schemaname = 'public';" $DB_NAME` ; do psql -c "ALTER TABLE $tbl OWNER TO $DB_USER" $DB_NAME ; done
    for tbl in `psql -qAt -c "SELECT table_name FROM information_schema.views WHERE table_schema = 'public';" $DB_NAME` ; do psql -c "ALTER TABLE $tbl OWNER TO $DB_USER" $DB_NAME ; done
    for tbl in `psql -qAt -c "SELECT sequence_name FROM information_schema.sequences WHERE sequence_schema = 'public';" $DB_NAME` ; do psql -c "ALTER TABLE $tbl OWNER TO $DB_USER" $DB_NAME ; done
.

  • Remove from a table all rows older than a month:

    $ sudo -u postgres psql -d database_id  --command "DELETE FROM smile_log WHERE log_date > current_date - interval '1 month';"

  • Extract an image that was saved in the database as base64 content, and save it on the file system:

    $ psql -d my_database -tc "COPY (SELECT decode(convert_from(image_bin, 'UTF-8'), 'base64') FROM res_partner WHERE id = 25) TO '/var/lib/postgresql/logo.png';"

  • Monitor queries being run in real time:

    $ watch -n 1 'sudo -u postgres psql --tuples-only --command "SELECT datname, procpid, date_trunc(\$\$second\$\$, age(current_timestamp, xact_start)), current_query FROM pg_stat_activity;"'

  • Disable all triggers of a table, excluding triggers that are used to implement foreign key constraints:

    $ ALTER TABLE table_id DISABLE TRIGGER ALL;

  • List all constraints of your database (source):

    SELECT tc.constraint_name,
tc.constraint_type,
tc.table_name,
kcu.column_name,
tc.is_deferrable,
tc.initially_deferred,
rc.match_option AS match_type,
rc.update_rule AS on_update,
rc.delete_rule AS on_delete,
ccu.table_name AS references_table,
ccu.column_name AS references_field
FROM information_schema.table_constraints tc

LEFT JOIN information_schema.key_column_usage kcu
ON tc.constraint_catalog = kcu.constraint_catalog
AND tc.constraint_schema = kcu.constraint_schema
AND tc.constraint_name = kcu.constraint_name

LEFT JOIN information_schema.referential_constraints rc
ON tc.constraint_catalog = rc.constraint_catalog
AND tc.constraint_schema = rc.constraint_schema
AND tc.constraint_name = rc.constraint_name

LEFT JOIN information_schema.constraint_column_usage ccu
ON rc.unique_constraint_catalog = ccu.constraint_catalog
AND rc.unique_constraint_schema = ccu.constraint_schema
AND rc.unique_constraint_name = ccu.constraint_name

WHERE lower(tc.constraint_type) in ('foreign key');

  • And finally, here is a list of great monitoring one-liners.