PostgreSQL

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Revision as of 17:20, 2 August 2010

PostgreSQL

PostgreSQL is an object-relational database management system (ORDBMS). The documentation of PostgreSQL 8.4.4 can be found here^[4]

Installation

• Install PostgreSQL

$ sudo apt-get install postgresql 

Administration

Roles (Users)

Setup Root User Password

• Set up the password of the PostgreSQL root user

$ sudo -u postgres psql postgres 

Welcome to psql 8.3.5, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

postgres=# ALTER USER postgres WITH ENCRYPTED PASSWORD 'password'; 

or

postgres=# \password postgres 

Use \quit or \q to quit psql.

postgres=# \q 

Create Role (User)

Creating a user in PostgreSQL is in fact creating a role. So there are two ways to do it. The first one is using CREATE ROLE^[5] SQL command and the other one is using the programme, createuser^[6].

CREATE ROLE

CREATE ROLE^[7]

CREATE ROLE role_name; 
CREATE ROLE role_name WITH LOGIN ENCRYPTED PASSWORD 'password'; 
CREATE USER role_name WITH ENCRYPTED PASSWORD 'password'; 

(CREATE USER == CREATE ROLE + LOGIN)

createuser

createuser [option...] [username] 

So to create a new user and a db belonging to him/her.

sudo -u postgres createuser -P username 
sudo -u postgres createdb -O username db_name 

-P: it will ask you to enter the password for the new user (role).

• Options^[8]

createuser accepts the following command-line arguments:

username

    Specifies the name of the PostgreSQL user to be created. This name must be different from all existing roles in this PostgreSQL installation. 
-s
--superuser

    The new user will be a superuser. 
-S
--no-superuser

    The new user will not be a superuser. This is the default. 
-d
--createdb

    The new user will be allowed to create databases. 
-D
--no-createdb

    The new user will not be allowed to create databases. This is the default. 
-r
--createrole

    The new user will be allowed to create new roles (that is, this user will have CREATEROLE privilege). 
-R
--no-createrole

    The new user will not be allowed to create new roles. This is the default. 
-l
--login

    The new user will be allowed to log in (that is, the user name can be used as the initial session user identifier). This is the default. 
-L
--no-login

    The new user will not be allowed to log in. (A role without login privilege is still useful as a means of managing database permissions.) 
-i
--inherit

    The new role will automatically inherit privileges of roles it is a member of. This is the default. 
-I
--no-inherit

    The new role will not automatically inherit privileges of roles it is a member of. 
-c number
--connection-limit number

    Set a maximum number of connections for the new user. The default is to set no limit. 
-P
--pwprompt

    If given, createuser will issue a prompt for the password of the new user. This is not necessary if you do not plan on using password authentication. 
-E
--encrypted

    Encrypts the user's password stored in the database. If not specified, the default password behavior is used. 
-N
--unencrypted

    Does not encrypt the user's password stored in the database. If not specified, the default password behavior is used. 
-e
--echo

    Echo the commands that createuser generates and sends to the server. 

You will be prompted for a name and other missing information if it is not specified on the command line.

createuser also accepts the following command-line arguments for connection parameters:

-h host
--host host

    Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket. 
-p port
--port port

    Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. 
-U username
--username username

    User name to connect as (not the user name to create). 
-w
--no-password

    Never issue a password prompt. If the server requires password authentication and a password is not available by other means such as a .pgpass file, the connection attempt will fail. This option can be useful in batch jobs and scripts where no user is present to enter a password. 
-W
--password

    Force createuser to prompt for a password (for connecting to the server, not for the password of the new user).

    This option is never essential, since createuser will automatically prompt for a password if the server demands password authentication. However, createuser will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt. 

View Roles

• To see all the exising roles.

SELECT * FROM pg_roles;

• To see the details of an existing role

SELECT role_name FROM pg_roles; 

Change Role

• ALTER ROLE^[9] SQL

ALTER ROLE role_name WITH LOGIN ENCRYPTED PASSWORD 'password'; 

Remove Role

• Using DROP ROLE^[10] SQL

DROP ROLE role_name; 

• Using dropuser^[11]

dropuser name 

Databases

List Databases

postgres=# \l 

Creating Database

• Using CREATE DATABASE^[12] SQL to create a new database.

CREATE DATABASE db_name 

CREATE DATABASE db_name OWNER role_name 

• Similar to creating a role, it is also possible to create a new database from the shell by using createdb^[13] command.

createdb [option...] [db_name] [description]

sudo -u postgres createuser -P username 
sudo -u postgres createdb -O username db_name 

-O owner
--owner owner
     Specifies the database user who will own the new database. 

Restart Server

To restart the server, /etc/init.d/postgresql-8.x (depending on the version).

sudo /etc/init.d/postgresql-8.4 restart 

Install pgAdmin III

$ sudo apt-get install pgadmin3 

References