Difference between revisions of "PostgreSQL"

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(Upgrading PostgreSQL: use the same initdb command as in #Installing PostgreSQL)
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[[Category:Database management systems]]
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[[Category:Relational DBMSs]]
 
[[it:PostgreSQL]]
 
[[it:PostgreSQL]]
 
[[ja:PostgreSQL]]
 
[[ja:PostgreSQL]]
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{{Related|PhpPgAdmin}}
 
{{Related|PhpPgAdmin}}
 
{{Related articles end}}
 
{{Related articles end}}
[http://www.postgresql.org/ PostgreSQL] is an open source, community driven, standard compliant object-relational database system.
+
[https://www.postgresql.org/ PostgreSQL] is an open source, community driven, standard compliant object-relational database system.
  
This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. Among other applications, PostgreSQL can be substituted for MySQL as part of the [[LAMP]] web stack.
+
== Installing PostgreSQL ==
  
== Installing PostgreSQL ==
+
{{Accuracy|Is it really necessary to set a password for the user?}}
  
[[Install]] the {{Pkg|postgresql}} package. Then [[Users_and_groups#Other_examples_of_user_management|set a password]] for the newly created ''postgres'' user.
+
[[Install]] the {{Pkg|postgresql}} package. Then [[Users_and_groups#Example_adding_a_user|set a password]] for the newly created ''postgres'' user.
  
 
Then, switch to the default PostgreSQL user ''postgres'' by executing the following command:
 
Then, switch to the default PostgreSQL user ''postgres'' by executing the following command:
Line 21: Line 21:
 
:{{bc|$ sudo -u postgres -i}}
 
:{{bc|$ sudo -u postgres -i}}
  
* Otherwise:
+
* Otherwise use [[su]]:
  
 
:{{bc|<nowiki>
 
:{{bc|<nowiki>
Line 28: Line 28:
 
</nowiki>}}
 
</nowiki>}}
  
See {{man|1|su}} or {{man|8|sudo}} for their usage.
+
See {{man|8|sudo}} or {{man|1|su}} for their usage.
  
 
{{Note|Commands that should be run as the postgres user are prefixed by {{ic|[postgres]$}} in this article.}}
 
{{Note|Commands that should be run as the postgres user are prefixed by {{ic|[postgres]$}} in this article.}}
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If these are the kind of lines you see, then the process succeeded. Return to the regular user using {{ic|exit}}.
 
If these are the kind of lines you see, then the process succeeded. Return to the regular user using {{ic|exit}}.
  
As root, [[start]] and [[enable]] {{ic|postgresql.service}}.
+
As root, [[start]] and [[enable]] the {{ic|postgresql.service}}. See [[#Upgrading PostgreSQL]] for necessary steps before installing new versions of the PostgreSQL packages.
  
 
{{Tip|If you change the root to something other than {{ic|/var/lib/postgres}}, you will have to [[edit]] the service file. If the root is under {{ic|home}}, make sure to set {{ic|ProtectHome}} to false.}}
 
{{Tip|If you change the root to something other than {{ic|/var/lib/postgres}}, you will have to [[edit]] the service file. If the root is under {{ic|home}}, make sure to set {{ic|ProtectHome}} to false.}}
  
{{Warning|If the database resides on a [[Btrfs]] file system, you should consider disabling [[Btrfs#Copy-on-Write (CoW)|Copy-on-Write]] for the directory before creating any database. If the database resides on a [[ZFS]] file system, you should consult [[ZFS#Database]] before creating any database.}}
+
{{Warning|
 +
* If the database resides on a [[Btrfs]] file system, you should consider disabling [[Btrfs#Copy-on-Write (CoW)|Copy-on-Write]] for the directory before creating any database.
 +
* If the database resides on a [[ZFS]] file system, you should consult [[ZFS#Database]] before creating any database.
 +
}}
  
 
== Create your first database/user ==
 
== Create your first database/user ==
Line 75: Line 78:
 
{{Tip|If you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).}}
 
{{Tip|If you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).}}
  
Become the postgres user. Add a new database user using the [http://www.postgresql.org/docs/current/static/app-createuser.html createuser] command:
+
Become the postgres user. Add a new database user using the [https://www.postgresql.org/docs/current/static/app-createuser.html createuser] command:
  
 
  [postgres]$ createuser --interactive
 
  [postgres]$ createuser --interactive
  
Create a new database over which the above user has read/write privileges using the [http://www.postgresql.org/docs/current/static/app-createdb.html createdb] command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add {{ic|-U ''database-username''}} to the following command):
+
Create a new database over which the above user has read/write privileges using the [https://www.postgresql.org/docs/current/static/app-createdb.html createdb] command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add {{ic|-U ''database-username''}} to the following command):
  
 
  $ createdb myDatabaseName
 
  $ createdb myDatabaseName
Line 87: Line 90:
 
=== Access the database shell ===
 
=== Access the database shell ===
  
Become the postgres user. Start the primary database shell, [http://www.postgresql.org/docs/current/static/app-psql.html psql], where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the {{ic|-d}} option to connect to the database you created (without specifying a database, {{ic|psql}} will try to access a database that matches your username).
+
Become the postgres user. Start the primary database shell, [https://www.postgresql.org/docs/current/static/app-psql.html psql], where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the {{ic|-d}} option to connect to the database you created (without specifying a database, {{ic|psql}} will try to access a database that matches your username).
  
 
  [postgres]$ psql -d myDatabaseName
 
  [postgres]$ psql -d myDatabaseName
Line 139: Line 142:
 
where {{ic|my_remote_client_ip_address}} is the IP address of the client.
 
where {{ic|my_remote_client_ip_address}} is the IP address of the client.
  
See the documentation for [http://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html pg_hba.conf].
+
See the documentation for [https://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html pg_hba.conf].
 +
 
 +
{{Note|Neither sending your plain password nor the md5 hash (used in the example above) over the Internet is secure if it is not done over an SSL-secured connection. See [https://www.postgresql.org/docs/current/static/ssl-tcp.html Secure TCP/IP Connections with SSL] for how to configure PostgreSQL with SSL.}}
  
 
After this you should [[restart]] {{ic|postgresql.service}} for the changes to take effect.
 
After this you should [[restart]] {{ic|postgresql.service}} for the changes to take effect.
  
{{Note|PostgreSQL uses port {{ic|5432}} by default for remote connections. Make sure this port is open and able to receive incoming connections.}}
+
{{Note|PostgreSQL uses port {{ic|5432}} by default for remote connections. Make sure this port is open in your [[firewall]] and able to receive incoming connections.}}
  
 
For troubleshooting take a look in the server log file:
 
For troubleshooting take a look in the server log file:
  
  $ journalctl -u postgresql
+
  $ journalctl -u postgresql.service
  
 
=== Configure PostgreSQL authenticate against PAM ===
 
=== Configure PostgreSQL authenticate against PAM ===
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The PostgreSQL server is however running without root privileges and will not be able to access {{ic|/etc/shadow}}. We can work around that by allowing the postgres group to access this file:
 
The PostgreSQL server is however running without root privileges and will not be able to access {{ic|/etc/shadow}}. We can work around that by allowing the postgres group to access this file:
  
  setfacl -m g:postgres:r /etc/shadow
+
  # setfacl -m g:postgres:r /etc/shadow
  
 
=== Change default data directory ===
 
=== Change default data directory ===
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== Administration tools ==
 
== Administration tools ==
  
 +
* {{App|[[Adminer]]|Web-based database management tool for multiple database systems.|https://www.adminer.org|{{AUR|adminer}}}}
 
* {{App|[[phpPgAdmin]]|Web-based administration tool for PostgreSQL.|http://phppgadmin.sourceforge.net|{{Pkg|phppgadmin}}}}
 
* {{App|[[phpPgAdmin]]|Web-based administration tool for PostgreSQL.|http://phppgadmin.sourceforge.net|{{Pkg|phppgadmin}}}}
* {{App|pgAdmin|GUI-based administration tool for PostgreSQL.|http://www.pgadmin.org/|{{Pkg|pgadmin4}}}}
+
* {{App|pgAdmin|GUI-based administration tool for PostgreSQL.|https://www.pgadmin.org/|{{Pkg|pgadmin4}}}}
  
== Setup HHVM to work with PostgreSQL ==
+
== Upgrading PostgreSQL ==
  
{{Out of date|hhvm-pgsql fails to compile against HHVM 3.7.0, but upstream has not resolved the problem yet. See https://github.com/PocketRent/hhvm-pgsql/issues/82|section=Setting up HHVM}}
+
Upgrading major PostgreSQL versions requires some extra maintenance.
  
$ git clone https://github.com/PocketRent/hhvm-pgsql.git
+
{{Note|
$ cd hhvm-pgsql
+
* Official PostgreSQL [https://www.postgresql.org/docs/current/static/upgrading.html upgrade documentation] should be followed.
 +
* From version {{ic|10.0}} onwards PostgreSQL [https://www.postgresql.org/about/news/1786/ changed its versioning scheme]. Earlier upgrade from version {{ic|9.''x''}} to {{ic|9.''y''}} was considered as major upgrade. Now upgrade from version {{ic|10.''x''}} to {{ic|10.''y''}} is considered as minor upgrade and upgrade from version {{ic|10.''x''}} to {{ic|11.''y''}} is considered as major upgrade.
 +
}}
  
If you do not use a nightly build, then run this command (verified on HHVM 3.6.1) to avoid compile errors:
+
{{Warning|The following instructions could cause data loss. '''Use at your own risk'''.}}
  
$ git checkout tags/3.6.0
+
It is recommended to add the following to your {{ic|/etc/pacman.conf}} file:
  
Then build the extension (if you do not need an improved support for Hack language, then remove -DHACK_FRIENDLY=ON):
+
IgnorePkg = postgresql*
  
  $ hphpize
+
This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in {{ic|pacman.conf}}. Minor version upgrades are safe to perform. However, if you do an accidental upgrade to a different major version, you might not be able to access any of your data. Always check the [https://www.postgresql.org/ PostgreSQL home page] to be sure of what steps are required for each upgrade. For a bit about why this is the case, see the [https://www.postgresql.org/support/versioning versioning policy].
$ cmake -DHACK_FRIENDLY=ON .
 
$ make
 
  
Then copy the built extension:
+
There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.
  
# cp pgsql.so /etc/hhvm/
+
For those wishing to use {{ic|pg_upgrade}}, a {{Pkg|postgresql-old-upgrade}} package is available that will always run one major version behind the real PostgreSQL package. This can be installed side-by-side with the new version of PostgreSQL.  
  
Add to /etc/hhvm/server.ini:
+
'''Do not run the following commands blindly without understanding what they do!''' Reference the [https://www.postgresql.org/docs/current/static/pgupgrade.html upstream pg_upgrade documentation] for details.
  
extension_dir = /etc/hhvm
+
Note that the databases cluster directory does not change from version to version, so before running {{ic|pg_upgrade}}, it is necessary to rename your existing data directory and migrate into a new directory. The new databases cluster must be initialized, as described in the [[#Installing PostgreSQL]] section.
hhvm.extensions[pgsql] = pgsql.so
 
  
== Upgrading PostgreSQL ==
+
When you are ready, stop the postgresql service, upgrade the following packages: {{Pkg|postgresql}}, {{Pkg|postgresql-libs}}, and {{Pkg|postgresql-old-upgrade}}. Finally upgrade the databases cluster.
  
Upgrading major PostgreSQL versions (i.e. from {{ic|9.''x''}} to {{ic|9.''y''}}) requires some extra maintenance.
+
Stop and make sure PostgreSQL is stopped:
  
{{Note|Official PostgreSQL [http://www.postgresql.org/docs/current/static/upgrading.html upgrade documentation] should be followed.}}
+
# systemctl stop postgresql
 +
# systemctl status postgresql
  
{{Warning|The following instructions could cause data loss. '''Use at your own risk'''.}}
+
Upgrade the packages:
  
It is recommended to add the following to your {{ic|/etc/pacman.conf}} file:
+
# pacman -S postgresql postgresql-libs postgresql-old-upgrade
  
IgnorePkg = postgresql postgresql-libs
+
Rename the databases cluster directory, and create an empty one:
  
This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in {{ic|pacman.conf}}. Minor version upgrades (e.g. 9.0.3 to 9.0.4) are safe to perform. However, if you do an accidental upgrade to a different major version (e.g. 9.0.x to 9.1.x), you might not be able to access any of your data. Always check the [http://www.postgresql.org/ PostgreSQL home page] to be sure of what steps are required for each upgrade. For a bit about why this is the case, see the [http://www.postgresql.org/support/versioning versioning policy].
+
  # mv /var/lib/postgres/data /var/lib/postgres/olddata
 +
# mkdir /var/lib/postgres/data /var/lib/postgres/tmp
 +
# chown postgres:postgres /var/lib/postgres/data /var/lib/postgres/tmp
 +
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'
  
There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.
+
Upgrade the cluster:
  
For those wishing to use {{ic|pg_upgrade}}, a {{Pkg|postgresql-old-upgrade}} package is available that will always run one major version behind the real PostgreSQL package. This can be installed side-by-side with the new version of PostgreSQL.
+
[postgres]$ cd /var/lib/postgres/tmp
 +
[postgres]$ pg_upgrade -b /opt/pgsql-9.6/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/data
  
When you are ready, upgrade the following packages: {{Pkg|postgresql}}, {{Pkg|postgresql-libs}}, and {{Pkg|postgresql-old-upgrade}}. Note that the data directory does not change from version to version, so before running {{ic|pg_upgrade}}, it is necessary to rename your existing data directory and migrate into a new directory. The new database must be initialized, as described near the top of this page.
+
{{ic|pg_upgrade}} will perform the upgrade and create some scripts in {{ic|/var/lib/postgres/tmp/}}. Follow the instructions given on screen and act accordingly. You may delete the {{ic|/var/lib/postgres/tmp}} directory once the upgrade is completely over.
  
# systemctl stop postgresql.service
+
Start the cluster:
# mv /var/lib/postgres/data /var/lib/postgres/olddata
 
# mkdir /var/lib/postgres/data
 
# chown postgres:postgres /var/lib/postgres/data
 
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'
 
  
The upgrade invocation will likely look something like the following. '''Do not run this command blindly without understanding what it does!''' Reference the [http://www.postgresql.org/docs/current/static/pgupgrade.html upstream pg_upgrade documentation] for details.
+
# systemctl start postgresql
  
[postgres]$ cd /tmp
+
=== Manual dump and reload ===
[postgres]$ pg_upgrade -b /opt/pgsql-9.6/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/data
 
  
=== Manual dump and reload ===
+
{{Style|Don't show basic systemctl commands, etc.}}
  
 
You could also do something like this (after the upgrade and install of {{Pkg|postgresql-old-upgrade}}).
 
You could also do something like this (after the upgrade and install of {{Pkg|postgresql-old-upgrade}}).
  
{{Note|Below are the commands for PostgreSQL 9.6. You can find similar commands in {{ic|/opt/}} for PostgreSQL 9.2.}}
+
{{Note|
 +
* Below are the commands for PostgreSQL 9.6. You can find similar commands in {{ic|/opt/}} for PostgreSQL 9.2.
 +
* If you had customized your {{ic|pg_hba.conf}} file, you may have to temporarily modify it to allow full access to old database cluster from local system. After upgrade is complete set your customization to new database cluster as well and [[restart]] {{ic|postgresql.service}}.
 +
}}
  
 
  # systemctl stop postgresql.service
 
  # systemctl stop postgresql.service
  # /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ start
+
  # mv /var/lib/postgres/data /var/lib/postgres/olddata
  # /opt/pgsql-9.6/bin/pg_dumpall >> old_backup.sql
+
# mkdir /var/lib/postgres/data
  # /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ stop
+
# chown postgres:postgres /var/lib/postgres/data
 +
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'
 +
[postgres]$ /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ start
 +
  [postgres]$ pg_dumpall -f /tmp/old_backup.sql
 +
  [postgres]$ /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ stop
 
  # systemctl start postgresql.service
 
  # systemctl start postgresql.service
  # psql -f old_backup.sql postgres
+
  [postgres]$ psql -f /tmp/old_backup.sql postgres
  
 
== Troubleshooting ==
 
== Troubleshooting ==
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=== Improve performance of small transactions ===
 
=== Improve performance of small transactions ===
  
If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning [http://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT synchronous_commit off] in the configuration. Beware of the [http://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT caveats], however.
+
If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning [https://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT synchronous_commit off] in the configuration. Beware of the [https://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT caveats], however.
  
 
{{hc|/var/lib/postgres/data/postgresql.conf|2=
 
{{hc|/var/lib/postgres/data/postgresql.conf|2=
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===  Cannot connect to database through pg_connect()  ===
 
===  Cannot connect to database through pg_connect()  ===
  
Install {{Pkg|php-pgsql}} and edit the {{ic|php.ini}} file uncommenting the lines {{ic|1=extension=pdo_pgsql.so}} and {{ic|1=extension=pgsql.so}}, then restart {{ic|httpd}}.
+
Install {{Pkg|php-pgsql}} and edit the {{ic|php.ini}} file uncommenting the lines {{ic|1=extension=pdo_pgsql}} and {{ic|1=extension=pgsql}}, then restart {{ic|httpd}}.

Latest revision as of 23:54, 2 May 2018

PostgreSQL is an open source, community driven, standard compliant object-relational database system.

Installing PostgreSQL

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: Is it really necessary to set a password for the user? (Discuss in Talk:PostgreSQL#)
Install the postgresql package. Then set a password for the newly created postgres user.

Then, switch to the default PostgreSQL user postgres by executing the following command:

  • If you have sudo and your username is in sudoers:
$ sudo -u postgres -i
  • Otherwise use su:
$ su
# su -l postgres

See sudo(8) or su(1) for their usage.

Note: Commands that should be run as the postgres user are prefixed by [postgres]$ in this article.

Before PostgreSQL can function correctly, the database cluster must be initialized:

[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'

Where:

  • the --locale is the one defined in the file /etc/locale.conf;
  • the -E is the default encoding of the database that will be created in the future;
  • and -D is the default location where the database cluster must be stored.

Many lines should now appear on the screen with several ending by ... ok:

The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.

The database cluster will be initialized with locale "en_GB.UTF-8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

fixing permissions on existing directory /var/lib/postgres/data ... ok
creating subdirectories ... ok
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting dynamic shared memory implementation ... posix
creating configuration files ... ok
creating template1 database in /var/lib/postgres/data/base/1 ... ok
initializing pg_authid ... ok
[...]

If these are the kind of lines you see, then the process succeeded. Return to the regular user using exit.

As root, start and enable the postgresql.service. See #Upgrading PostgreSQL for necessary steps before installing new versions of the PostgreSQL packages.

Tip: If you change the root to something other than /var/lib/postgres, you will have to edit the service file. If the root is under home, make sure to set ProtectHome to false.
Warning:
  • If the database resides on a Btrfs file system, you should consider disabling Copy-on-Write for the directory before creating any database.
  • If the database resides on a ZFS file system, you should consult ZFS#Database before creating any database.

Create your first database/user

Tip: If you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).

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

[postgres]$ createuser --interactive

Create a new database over which the above user has read/write privileges using the createdb command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add -U database-username to the following command):

$ createdb myDatabaseName

Familiarize with PostgreSQL

Access the database shell

Become the postgres user. Start the primary database shell, psql, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the -d option to connect to the database you created (without specifying a database, psql will try to access a database that matches your username).

[postgres]$ psql -d myDatabaseName

Some helpful commands:

Get help:

=> \help

Connect to a particular database:

=> \c <database>

List all users and their permission levels:

=> \du

Show 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. To see all meta-commands run:

=> \?

Optional configuration

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 configuration files, including the pg_hba.conf.

Note: By default, this folder will not be browsable or searchable by a regular user. This is why find and locate are not finding the configuration files.

Edit the file /var/lib/postgres/data/postgresql.conf. In the connections and authentications section, add the listen_addresses line to your needs:

listen_addresses = 'localhost,my_local_ip_address'
#You can use '*' to listen on all local addresses

Take a careful look at the other lines.

Host-based authentication is configured in /var/lib/postgres/data/pg_hba.conf. This file controls which hosts are allowed to connect. Note that the defaults allow any local user to connect as any database user, including the database superuser. Add a line like the following:

# IPv4 local connections:
host   all   all   my_remote_client_ip_address/32   md5

where my_remote_client_ip_address is the IP address of the client.

See the documentation for pg_hba.conf.

Note: Neither sending your plain password nor the md5 hash (used in the example above) over the Internet is secure if it is not done over an SSL-secured connection. See Secure TCP/IP Connections with SSL for how to configure PostgreSQL with SSL.

After this you should restart postgresql.service for the changes to take effect.

Note: PostgreSQL uses port 5432 by default for remote connections. Make sure this port is open in your firewall and able to receive incoming connections.

For troubleshooting take a look in the server log file:

$ journalctl -u postgresql.service

Configure PostgreSQL authenticate against PAM

PostgreSQL offers a number of authentication methods. If you would like to allow users to authenticate with their system password, additional steps are necessary. First you need to enable PAM for the connection.

For example, the same configuration as above, but with PAM enabled:

# IPv4 local connections:
host   all   all   my_remote_client_ip_address/32   pam

The PostgreSQL server is however running without root privileges and will not be able to access /etc/shadow. We can work around that by allowing the postgres group to access this file:

# setfacl -m g:postgres:r /etc/shadow

Change default data directory

The default directory where all your newly created databases will be stored is /var/lib/postgres/data. To change this, follow these steps:

Create the new directory and make the postgres user its owner:

# mkdir -p /pathto/pgroot/data
# chown -R postgres:postgres /pathto/pgroot

Become the postgres user, and initialize the new cluster:

[postgres]$ initdb -D /pathto/pgroot/data

Edit postgresql.service to create a drop-in file and override the Environment and PIDFile settings. For example:

[Service]
Environment=PGROOT=/pathto/pgroot
PIDFile=/pathto/pgroot/data/postmaster.pid

If you want to use /home directory for default directory or for tablespaces, add one more line in this file:

ProtectHome=false

Change default encoding of new databases to UTF-8

Note: If you ran initdb with -E UTF8 these steps are not required.

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 a new database, one of the options is to change on-site template1. To do this, log into PostgreSQL shell (psql) and execute the following:

First, we need to drop template1. Templates cannot be dropped, so we first modify it so it is an ordinary database:

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

Now we can drop it:

DROP DATABASE template1;

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

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

Now modify template1 so it is actually a template:

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

Optionally, if you do not want anyone connecting to this template, set datallowconn to FALSE:

UPDATE pg_database SET datallowconn = FALSE WHERE datname = 'template1';
Note: This last step can create problems when upgrading via pg_upgrade.

Now you can create a new database:

[postgres]$ createdb blog

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

\l
                              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     |

Administration tools

  • Adminer — Web-based database management tool for multiple database systems.
https://www.adminer.org || adminerAUR
  • phpPgAdmin — Web-based administration tool for PostgreSQL.
http://phppgadmin.sourceforge.net || phppgadmin
  • pgAdmin — GUI-based administration tool for PostgreSQL.
https://www.pgadmin.org/ || pgadmin4

Upgrading PostgreSQL

Upgrading major PostgreSQL versions requires some extra maintenance.

Note:
  • Official PostgreSQL upgrade documentation should be followed.
  • From version 10.0 onwards PostgreSQL changed its versioning scheme. Earlier upgrade from version 9.x to 9.y was considered as major upgrade. Now upgrade from version 10.x to 10.y is considered as minor upgrade and upgrade from version 10.x to 11.y is considered as major upgrade.
Warning: The following instructions could cause data loss. Use at your own risk.

It is recommended to add the following to your /etc/pacman.conf file:

IgnorePkg = postgresql*

This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in pacman.conf. Minor version upgrades are safe to perform. However, if you do an accidental upgrade to a different major version, you might not be able to access any of your data. Always check the PostgreSQL home page to be sure of what steps are required for each upgrade. For a bit about why this is the case, see the versioning policy.

There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.

For those wishing to use pg_upgrade, a postgresql-old-upgrade package is available that will always run one major version behind the real PostgreSQL package. This can be installed side-by-side with the new version of PostgreSQL.

Do not run the following commands blindly without understanding what they do! Reference the upstream pg_upgrade documentation for details.

Note that the databases cluster directory does not change from version to version, so before running pg_upgrade, it is necessary to rename your existing data directory and migrate into a new directory. The new databases cluster must be initialized, as described in the #Installing PostgreSQL section.

When you are ready, stop the postgresql service, upgrade the following packages: postgresql, postgresql-libs, and postgresql-old-upgrade. Finally upgrade the databases cluster.

Stop and make sure PostgreSQL is stopped:

# systemctl stop postgresql
# systemctl status postgresql

Upgrade the packages:

# pacman -S postgresql postgresql-libs postgresql-old-upgrade

Rename the databases cluster directory, and create an empty one:

# mv /var/lib/postgres/data /var/lib/postgres/olddata
# mkdir /var/lib/postgres/data /var/lib/postgres/tmp
# chown postgres:postgres /var/lib/postgres/data /var/lib/postgres/tmp
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'

Upgrade the cluster:

[postgres]$ cd /var/lib/postgres/tmp
[postgres]$ pg_upgrade -b /opt/pgsql-9.6/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/data

pg_upgrade will perform the upgrade and create some scripts in /var/lib/postgres/tmp/. Follow the instructions given on screen and act accordingly. You may delete the /var/lib/postgres/tmp directory once the upgrade is completely over.

Start the cluster:

# systemctl start postgresql

Manual dump and reload

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements.Tango-edit-clear.png

Reason: Don't show basic systemctl commands, etc. (Discuss in Talk:PostgreSQL#)

You could also do something like this (after the upgrade and install of postgresql-old-upgrade).

Note:
  • Below are the commands for PostgreSQL 9.6. You can find similar commands in /opt/ for PostgreSQL 9.2.
  • If you had customized your pg_hba.conf file, you may have to temporarily modify it to allow full access to old database cluster from local system. After upgrade is complete set your customization to new database cluster as well and restart postgresql.service.
# systemctl stop postgresql.service
# mv /var/lib/postgres/data /var/lib/postgres/olddata
# mkdir /var/lib/postgres/data
# chown postgres:postgres /var/lib/postgres/data
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'
[postgres]$ /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ start
[postgres]$ pg_dumpall -f /tmp/old_backup.sql
[postgres]$ /opt/pgsql-9.6/bin/pg_ctl -D /var/lib/postgres/olddata/ stop
# systemctl start postgresql.service
[postgres]$ psql -f /tmp/old_backup.sql postgres

Troubleshooting

Improve performance of small transactions

If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning synchronous_commit off in the configuration. Beware of the caveats, however.

/var/lib/postgres/data/postgresql.conf
synchronous_commit = off

Prevent disk writes when idle

PostgreSQL periodically updates its internal "statistics" file. By default, this file is stored on disk, which prevents disks from spinning down on laptops and causes hard drive seek noise. It is simple and safe to relocate this file to a memory-only file system with the following configuration option:

/var/lib/postgres/data/postgresql.conf
stats_temp_directory = '/run/postgresql'

Cannot connect to database through pg_connect()

Install php-pgsql and edit the php.ini file uncommenting the lines extension=pdo_pgsql and extension=pgsql, then restart httpd.