PostgreSQL console commands

    # show a list of databases

        \l

    # show all users

        select * from pg_user;

    # show all tables (including system tables)

        select * from pg_tables;

    # show tables in the current context (database/schema)

        \d

    # change current database

        \c database;

    # show all schemas in the current database

        \dn

    # Grant permissions on a schema to a user

        GRANT ALL ON myschema TO user;

    # show help

        \?

    # copy a table to a tab delimeted file

        COPY table TO 'table.txt';

    # load a table from a tab delimeted file

        COPY table FROM 'table.txt';

    # show permissions on database objects

        \z [object]

   
        r -- SELECT ("read")
        w -- UPDATE ("write")
        a -- INSERT ("append")
        d -- DELETE
        R -- RULE
        x -- REFERENCES (foreign keys)
        t -- TRIGGER
        X -- EXECUTE
        U -- USAGE
        C -- CREATE
        T -- TEMPORARY
        arwdRxt -- ALL PRIVILEGES (for tables)
        * -- grant option for preceding privilege
        /yyyy -- user who granted this privilege
    # Run the vacuum utility

        vacuumdb --verbose --analyze --all

    Note: vacuum reclaims space from deleted records and updates indexes. It should be set up in cron. Newer versions of postgresql may run vacuum automatically.


    Increase perfomance with shared memory


    One effective performance tuning tip for Postgresql is to increase the shared
    memory buffers. This might require adding RAM to the server. Many Linux distros
    default to 32MB of shared memory, controlled by two kernel parameters:
    /proc/sys/kernel/shmmax
    /proc/sys/kernel/shmall


    These values can be changed at run time, but it is better to set them at boot
    using the /etc/sysctl.conf file. This increases shared memory to 1GB:
    # increase shared buffers for postgres at boot
    kernel.shmmax=1073741824
    kernel.shmall=1073741824
    Then, tell PostgreSQL to use 768MB of the 1GB available in the
    /var/lib/pgsql/data/postgresql.conf file:
    shared_buffers = 98304 # min 16, at least max_connections*2, 8KB each


    Restart PostgreSQL for the change to take effect.