Difference between revisions of "PostgreSQL"

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*Start the primary db shell, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.
*Start the primary db shell, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.
<pre>$ psql</pre>
<pre>$ psql</pre>
**You can optionally use `psql <database_name>` to administer an individual database.
:''--You can optionally use `psql <database_name>` to administer an individual database.''
*Connect to a particular database
*Connect to a particular database
<pre>=> \c <database> </pre>
<pre>=> \c <database> </pre>

Revision as of 15:43, 13 February 2009

This document describes how to set up PostgreSQL and integrate it with PHP and Apache. It also describes how to configure PostgreSQL to be accessible from a remote client. PHP and Apache are assumed to be already be set up. If you need help setting up either of those two, see the LAMP page and follow all of the sections except the one related to MySQL.

Installing PostgreSQL

  1. Install the package
    $ sudo pacman -Sy postgresql
  2. Setup and start the PostgreSQL server (the first time that this is run it will create the data directory and users needed to run the server. As such you will see a lot of output.
    $ sudo /etc/rc.d/postgresql start
  3. Check to make sure the postgres user is created (and is in the postgres group).
    $ groups postgres 
  4. (Optional) Add postgresql to the list of daemons that start on system startup in the /etc/rc.conf file

Configure PostgreSQL to be accessible from remote

The PostgreSQL database server configuration file is postgresql.conf. This file is located in the data directory of the server, typically /var/lib/postgres/data. This folder also houses the other main config files, including the pg_hba.conf. Note: By default this folder will not even be browseable (or searchable) by a regular user, if you are wondering why `find` or `locate` isn't finding the conf files, this is the reason (threw me for a loop the first time I installed).

  1. As root user edit the file
    $ sudo vim /var/lib/postgres/data/postgresql.conf
  2. In the connections and authentications section uncomment or edit the listen_addresses line to your needs
    listen_addresses = '*'
    and take a careful look at the other lines.
  3. Hereafter insert the following line in the host-based authentication file /var/lib/postgres/data/pg_hba.conf. This file controls which hosts are allowed to connect, so be careful.
    # IPv4 local connections: <br>host   all   all   your_desired_ip_address/32   trust
    whereas your_desired_ip_address is the ip address of the client.
  4. After this you should restart the daemon process for the changes to take effect with
    $ sudo /etc/rc.d/postgresql restart

Postgresql uses port 5432 by default for remote connections. So make sure this port is open and able to receive incoming connections

For troubleshooting take a look in the server log file
tail /var/log/postgresql.log

Creating Your First Database

  1. Become the postgres user (This user was created when "/etc/rc.d/postgres start" was run)
    su root
     su - postgres 
  2. Add a new database user
     createuser -DRSP username 
  3. Create a new database over which that user has read/write privileges
     createdb -O username databasename 
  4. That's It! Your database has been created.

Familiarizing Yourself with PostgreSQL

Create a role for your user (you)

createuser $USER 
Shall the new role be a superuser? (y/n)  n
Shall the new role be allowed to create databases? (y/n)  y
Shall the new role be allowed to create more new roles? (y/n)  y
  • You can also just choose to make a superuser (however the postgresql team does not advise this, for security reasons, your needs may vary).

This will create a database user, with the same name as your system username ($USER). Why do this? This allows you to access the postgresql database shell without having to specify a user to login as (which makes it quite convenient).

Access the database shell

  • Become the postgres user the first time, so we can assign permissions to you (your primary user)
$ sudo su postgres 
  • Start the primary db shell, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.
$ psql
--You can optionally use `psql <database_name>` to administer an individual database.
  • Connect to a particular database
=> \c <database> 
  • List all users and their permission levels
=> \du 
  • Shows summary information about all tables in the current database
=> \dt 

There are of course many more commands, but these should help you get started.

Configure PostgreSQL to Work With PHP

  1. Open the file /etc/php/php.ini with your editor of choice, e.g.,
    # vim /etc/php/php.ini
  2. Find the line that starts with, ";extension=pgsql.so" and change it to, "extension=pgsql.so". (Just remove the preceding ";"). If you need PDO, do the same thing with ";extension=pdo_pgsql.so". If this lines are not present, add it. This lines may be in the "Dynamic Extensions" section of the file, or toward the very end of the file.
  3. Restart the Apache web server
    # /etc/rc.d/httpd restart

Installing phpPgAdmin (optional)

phpPgAdmin is a web-based administration tool for PostgreSQL. It can be installed two ways.

Option A: install via Pacman (preferred)

  1. Make sure that the [community] repo is enabled.
  2. Install the package via Pacman
    # pacman -Sy phppgadmin

Option B: install via a manual install (the old way)

  1. Download the latest .bz2 file from here into the root of your server directory
    wget -P /home/httpd/html http://downloads.sourceforge.net/phppgadmin/phpPgAdmin-4.1.3.tar.bz2
  2. Extract the file into the new directory
    tar -C /home/httpd/html/ -jxvf /home/httpd/html/phpPgAdmin-4.1.3.tar.bz2
  3. Remove the tar file
    rm /home/httpd/html/phpPgAdmin-4.1.3.tar.bz2
  4. Change the name of the directory created in the previous step to include the version number (this will help in the future when upgrading)
    mv /home/httpd/html/phpPgAdmin /home/httpd/html/phpPgAdmin-4.1.3/
  5. Create a link to that directory (for ease of linking and upgrading)
    ln -s /home/httpd/html/phpPgAdmin-4.1.3/ /home/httpd/html/phpPgAdmin
  6. Copy the included generic config file
    cp /home/httpd/html/phpPgAdmin/conf/config.inc.php-dist /home/httpd/html/phpPgAdmin/conf/config.inc.php

The config file is located at /home/httpd/html/phpPgAdmin/conf/config.inc.php. No changes should be required. Check this page for any other setup questions that you might have.

Upgrading Postgresql (optional and dangerous)

  1. First thing: these instructions could cause data loss. Use at your own risk. They work for me, but things change and nothing is guaranteed.
  2. I would highly suggest adding the line
    IgnorePkg = postgresql
    to /etc/pacman.conf. This will make sure that you don't accidentally upgrade the database to an incompatible version. If you did an accidental upgrade you might not be able to access any of your data. Always check the Postgresql home page (http://www.postgresql.org/) to be sure of what steps are required for each upgrade. For a bit about why this is the case see this.
  3. How to dump all of your data, upgrade PostgreSQL, and then restore all of your data (this may not be necessary for every upgrade, see #2 above)
    1. Become the root user
    2. Become the postgres user
      su postgres
    3. Change the current directory to one that the postgres user can write to
      eg. cd ~/data/
    4. Dump the current contents of the database
      pg_dumpall > pgs_db.out
      Unless you have a .pgpass file setup, you will be required to enter your password a few times (the number of times is roughly equal to the number of databases that you have + 2). One problem occurs if you don't have a password defined for the postgres user but you require local users to authenticate. In this case you will be asked to give a password that doesn't exist. To work around this problem, add a line to your pg_hba.conf file to trust the postgres user. You can remove this line after the upgrade is complete. So, the first line of the 'local' section of pg_hba.conf would look something like this:
      local     all postgres                                trust
    5. Log out of the postgres user and return to superuser
    6. Stop the PostgreSQL server
      /etc/rc.d/postresql stop
    7. Move Postgresql's data directory
      mv /var/lib/postgres /var/lib/postgres_old
    8. Upgrade postgresql
      pacman -Sy postgresql
    9. Start the PostgreSQL server (this will create all needed files and directories)
      /etc/rc.d/postgresql start
    10. Become the postgres user
      su postgres
    11. Change the current directory to the directory that you dumped the data out to (in step 4 above)
      eg. cd /var/lib/postgres_old/data/
    12. Restore the database
      psql -e template1 -f pgs_db.out

More Resources

Official PostgreSQL Homepage