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

1 $ 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:

1 $ 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:

1 $ psql --list -U kevin

Create a new kevin_db database with the kevin user:

1 $ createdb -U kevin kevin_db

Remove the database we created above:

1 $ dropdb kevin_db -U kevin

To connect to a particular database:

1 $ psql -d database_id

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

1 $ 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:

1 $ pg_dump my_database --schema-only --table=my_table

Dump a database in a compressed format:

1 $ pg_dump my_database -v --format=c --file=/var/lib/postgresql/my_database-db-2011-12-19.dump

Restore a compressed dump:

1 $ 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:

1 $ psql --username kevin -d kevin_db < ./database_dump.sql

Search if kevin is a PostgreSQL user:

1 $ 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:

1 $ 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):

1 $ 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:

1 $ su - postgres <<-'.'
2     DB_NAME=testdb
3     DB_USER=openerp
4     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
5     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
6     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
7 .

Remove from a table all rows older than a month:

1 $ 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:

1 $ 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:

1 $ 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:

1 $ 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.