Difference between revisions of "PostgreSQL"

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[[Category:Web Server (English)]]
 
[[Category:Web Server (English)]]
  
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, although the instructions work nicely with [[nginx]] as well. 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]].
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This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. If you need help setting up the rest of a web stack, see the [[LAMP]] page and follow all of the sections except the one related to [[MySQL]].
 +
 
 +
Several sections have instructions stating "become the postgres user". If sudo is installed, execute the following to get a shell as the postgres user:
 +
sudo -i -u postgres
 +
 
 +
Otherwise su can be used:
 +
su root
 +
su - postgres
  
 
==Installing PostgreSQL==
 
==Installing PostgreSQL==
Line 10: Line 17:
 
*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.)  
 
*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
 
  $ sudo /etc/rc.d/postgresql start
*Check to make sure the postgres user is created and is in the postgres group.
 
$ groups postgres
 
 
*(Optional) Add postgresql to the list of daemons that start on system startup in the /etc/rc.conf file
 
*(Optional) Add postgresql to the list of daemons that start on system startup in the /etc/rc.conf file
  
 
==Creating Your First Database/User==
 
==Creating Your First Database/User==
*Become the postgres user (This user was created when "/etc/rc.d/postgres start" was run)
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*Become the postgres user. Add a new database user using the [http://www.postgresql.org/docs/9.0/static/app-createuser.html createuser] command.
su root
+
su - postgres
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*Add a new database user
+
[http://www.postgresql.org/docs/9.0/static/app-createuser.html createuser] -D -R -S -P <username>
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-D User cannot create databases<br>
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-R User cannot create roles<br>
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-S User will not be a superuser<br>
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-P Prompt for password will be issued<br>
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Alternatively, you can use the createuser without parameter.  Questions will be asked:
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If you create a user as per your login user ($USER) it allows you to access the postgresql database shell without having to specify a user to login (which makes it quite convenient).
# createuser <username>
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Shall the new role be a superuser? (y/n) n
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Shall the new role be allowed to create databases? (y/n)  y
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Shall the new role be allowed to create more new roles? (y/n) y
+
  
The password can be changed from the psql command promt (su - postgres, then psql):
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*Create a new database over which the above user has read/write privileges using the [http://www.postgresql.org/docs/9.0/static/app-createdb.html createdb] command.
ALTER USER <username> WITH PASSWORD 'mypassword';
+
 
+
If you create a user as per your login user ($USER) it allows you to access the postgresql database shell without having to specify a user to login as (which makes it quite convenient).
+
 
+
*Create a new database over which that user has read/write privileges
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[http://www.postgresql.org/docs/8.3/static/app-createdb.html createdb] -O username databasename [-E database_encoding -T template]
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The enclosed text is optional, where database_encoding for instance can be UTF8 and template can be template0 (this is necessary if used UTF8 as encoding).
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*That's It! Your database has been created.
+
  
 
==Familiarizing Yourself with PostgreSQL==
 
==Familiarizing Yourself with PostgreSQL==
  
 
===Access the database shell===
 
===Access the database shell===
*Become the postgres user the first time, so we can assign permissions to you (your primary user)
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*Become the postgres user. Start the primary db shell, [http://www.postgresql.org/docs/8.3/static/app-psql.html psql], where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.
$ sudo su postgres
+
 
 +
Some helpful commands:
  
*Start the primary db shell, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.
 
$ [http://www.postgresql.org/docs/8.3/static/app-psql.html psql]
 
:''--You can optionally use `psql <database_name>` to administer an individual database.''
 
 
*Connect to a particular database
 
*Connect to a particular database
 
  => \c <database>
 
  => \c <database>
Line 61: Line 44:
 
There are of course many more meta-commands, but these should help you get started.
 
There are of course many more meta-commands, but these should help you get started.
  
==Configure PostgreSQL to be accessible from remote==
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==Configure PostgreSQL to be accessible from remote hosts==
 
The PostgreSQL database server configuration file is <code>postgresql.conf</code>. This file is located in the data directory of the server, typically <code>/var/lib/postgres/data</code>. This folder also houses the other main config files, including the <code>pg_hba.conf</code>.
 
The PostgreSQL database server configuration file is <code>postgresql.conf</code>. This file is located in the data directory of the server, typically <code>/var/lib/postgres/data</code>. This folder also houses the other main config files, including the <code>pg_hba.conf</code>.
 +
 
{{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).}}
 
{{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).}}
 +
 
#As root user edit the file<br><pre>$ sudo vim /var/lib/postgres/data/postgresql.conf</pre>
 
#As root user edit the file<br><pre>$ sudo vim /var/lib/postgres/data/postgresql.conf</pre>
 
#In the connections and authentications section uncomment or edit the <code>listen_addresses</code> line to your needs<br><pre>listen_addresses = '*'</pre>and take a careful look at the other lines.
 
#In the connections and authentications section uncomment or edit the <code>listen_addresses</code> line to your needs<br><pre>listen_addresses = '*'</pre>and take a careful look at the other lines.
#Hereafter insert the following line in the host-based authentication file <code>/var/lib/postgres/data/pg_hba.conf</code>. This file controls which hosts are allowed to connect, '''so be careful'''.<br><pre># IPv4 local connections: <br>host  all  all  your_desired_ip_address/32  trust</pre>whereas <code>your_desired_ip_address</code> is the ip address of the client.
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#Hereafter insert the following line in the host-based authentication file <code>/var/lib/postgres/data/pg_hba.conf</code>. This file controls which hosts are allowed to connect, '''so be careful'''.
 +
# IPv4 local connections:
 +
host  all  all  your_desired_ip_address/32  trust
 +
where <code>your_desired_ip_address</code> is the IP address of the client.
 
#After this you should restart the daemon process for the changes to take effect with<br><pre>$ sudo /etc/rc.d/postgresql restart</pre>
 
#After this you should restart the daemon process for the changes to take effect with<br><pre>$ sudo /etc/rc.d/postgresql restart</pre>
  
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==Change Default Data Dir (Optional)==
 
==Change Default Data Dir (Optional)==
By default, when installing PostgreSQL the directory were all your newly created databases will be stored is <code>/var/lib/postgresql/data</code>. If you want to change this behaviour, you have to follow these steps:
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By default, when installing PostgreSQL the directory were all your newly created databases will be stored is <code>/var/lib/postgresql/data</code>. If you want to change this behavior, you have to follow these steps:
  
 
1. Create the new directory and assign it to user <code>postgres</code> (you eventually have to become root) :
 
1. Create the new directory and assign it to user <code>postgres</code> (you eventually have to become root) :

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This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. If you need help setting up the rest of a web stack, see the LAMP page and follow all of the sections except the one related to MySQL.

Several sections have instructions stating "become the postgres user". If sudo is installed, execute the following to get a shell as the postgres user:

sudo -i -u postgres

Otherwise su can be used:

su root
su - postgres

Installing PostgreSQL

  • Install postgresql
$ sudo pacman -S postgresql
  • 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
  • (Optional) Add postgresql to the list of daemons that start on system startup in the /etc/rc.conf file

Creating Your First Database/User

  • Become the postgres user. Add a new database user using the createuser command.

If you create a user as per your login user ($USER) it allows you to access the postgresql database shell without having to specify a user to login (which makes it quite convenient).

  • Create a new database over which the above user has read/write privileges using the createdb command.

Familiarizing Yourself with PostgreSQL

Access the database shell

  • Become the postgres user. Start the primary db shell, psql, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands.

Some helpful commands:

  • 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
  • exit/quit the psql shell
=> \q or CTRL+d

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

Configure PostgreSQL to be accessible from remote hosts

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:
host   all   all   your_desired_ip_address/32   trust

where your_desired_ip_address is the IP address of the client.

  1. After this you should restart the daemon process for the changes to take effect with
    $ sudo /etc/rc.d/postgresql restart
Note: 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

Configure PostgreSQL to Work With PHP

  1. Install the PHP-PostgreSQL modules
    # pacman -S php-pgsql 
  2. Open the file /etc/php/php.ini with your editor of choice, e.g.,
    # vim /etc/php/php.ini
  3. 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.so" and ";extension=pdo_pgsql.so". If these lines are not present, add them. These lines may be in the "Dynamic Extensions" section of the file, or toward the very end of the file.
  4. Restart the Apache web server
    # /etc/rc.d/httpd restart

Change Default Data Dir (Optional)

By default, when installing PostgreSQL the directory were all your newly created databases will be stored is /var/lib/postgresql/data. If you want to change this behavior, you have to follow these steps:

1. Create the new directory and assign it to user postgres (you eventually have to become root) :

# mkdir /mypath/mydatadir
# chown postgres:postgres /mypath/mydatadir

2. Become the postgres user, and initialize the new cluster:

$ initdb -D /mypath/mydatadir;

3. Now, as root user, stop the daemon (if it's currently running ) and restart specifying the new data dir:

# /etc/rc.d/postgresql stop
# /etc/rc.d/postgresql start -D /mypath/mydatadir

Note that, unless you change the default behaviour by editing the file /etc/rc.d/postgresql, you have to specify the data dir, with the -D option, each time you start PostgreSQL daemon.

Change Default Encoding of New Databases To UTF-8 (Optional)

When creating a new database (e.g. with createdb blog) PostgreSQL actually copies a template database. There are two predefined templates: template0 is vanilla, while template1 is meant as an on-site template changeable by the administrator and is used by default. In order to change the encoding of new database, one of the options is to change on-site template1. To do this, log into PostgresSQL shell (psql) and execute the following:

1. First, we need to drop template1. Templates can't be dropped, so we first modify it so it's an ordinary database:

UPDATE pg_database SET datistemplate = FALSE WHERE datname = 'template1';

2. Now we can drop it:

DROP DATABASE template1;

3. The next step is to create a new database from template0, with a new default encoding:

CREATE DATABASE template1 WITH TEMPLATE = template0 ENCODING = 'UNICODE';

4. Now modify template1 so it's actually a template:

UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template1'; 

5. (RECOMMENDED) PostgreSQL documentation advises to VACUUM FREEZE the template:

\c template1
VACUUM FREEZE;

6. (OPTIONAL) If you don't want anyone connecting to this template, set datallowconn to FALSE:

UPDATE pg_database SET datallowconn = FALSE WHERE datname = 'template1';

Now you can create a new database by running from regular shell:

su - 
su - postgres
createdb blog;

If you log in back to psql and check the databases, you should see the proper encoding of your new database:

\l

returns

                              List of databases
  Name    |  Owner   | Encoding  | Collation | Ctype |   Access privileges   
-----------+----------+-----------+-----------+-------+----------------------
blog      | postgres | UTF8      | C         | C     | 
postgres  | postgres | SQL_ASCII | C         | C     | 
template0 | postgres | SQL_ASCII | C         | C     | =c/postgres
                                                     : postgres=CTc/postgres
template1 | postgres | UTF8      | C         | C     |

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 -S 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.

Installing pgAdmin (optional)

pgAdmin is a GUI-based administration tool for PostgreSQL.

  1. Install the package via Pacman
    # pacman -S pgadmin3

Upgrading Postgresql

Warning: Official postgresql upgrade documentation should be followed.

First thing: these instructions could cause data loss. Use at your own risk. They work for me, but things change and nothing is guaranteed.

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.

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)

Become the root user

su

Become the postgres user

su postgres

Change the current directory to one that the postgres user can write to

eg. cd ~/data/

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

Log out of the postgres user and return to superuser

exit

Stop the PostgreSQL server

/etc/rc.d/postgresql stop

Move Postgresql's data directory

mv /var/lib/postgres /var/lib/postgres_old

Upgrade postgresql

pacman -S postgresql

Start the PostgreSQL server (this will create all needed files and directories)

/etc/rc.d/postgresql start

Become the postgres user

su postgres

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/

Restore the database

psql -e template1 -f pgs_db.out

More Resources