depot/third_party/nixpkgs/nixos/modules/services/databases/postgresql.xml

<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="module-postgresql">
 <title>PostgreSQL</title>
<!-- FIXME: render nicely -->
<!-- FIXME: source can be added automatically -->
 <para>
  <emphasis>Source:</emphasis> <filename>modules/services/databases/postgresql.nix</filename>
 </para>
 <para>
  <emphasis>Upstream documentation:</emphasis> <link xlink:href="http://www.postgresql.org/docs/"/>
 </para>
<!-- FIXME: more stuff, like maintainer? -->
 <para>
  PostgreSQL is an advanced, free relational database.
<!-- MORE -->
 </para>
 <section xml:id="module-services-postgres-configuring">
  <title>Configuring</title>

  <para>
   To enable PostgreSQL, add the following to your <filename>configuration.nix</filename>:
<programlisting>
<xref linkend="opt-services.postgresql.enable"/> = true;
<xref linkend="opt-services.postgresql.package"/> = pkgs.postgresql_11;
</programlisting>
   Note that you are required to specify the desired version of PostgreSQL (e.g. <literal>pkgs.postgresql_11</literal>). Since upgrading your PostgreSQL version requires a database dump and reload (see below), NixOS cannot provide a default value for <xref linkend="opt-services.postgresql.package"/> such as the most recent release of PostgreSQL.
  </para>

<!--
<para>After running <command>nixos-rebuild</command>, you can verify
whether PostgreSQL works by running <command>psql</command>:

<screen>
<prompt>$ </prompt>psql
psql (9.2.9)
Type "help" for help.

<prompt>alice=></prompt>
</screen>
-->

  <para>
   By default, PostgreSQL stores its databases in <filename>/var/lib/postgresql/$psqlSchema</filename>. You can override this using <xref linkend="opt-services.postgresql.dataDir"/>, e.g.
<programlisting>
<xref linkend="opt-services.postgresql.dataDir"/> = "/data/postgresql";
</programlisting>
  </para>
 </section>
 <section xml:id="module-services-postgres-upgrading">
  <title>Upgrading</title>

  <para>
   Major PostgreSQL upgrade requires PostgreSQL downtime and a few imperative steps to be called. To simplify this process, use the following NixOS module:
<programlisting>
  containers.temp-pg.config.services.postgresql = {
    enable = true;
    package = pkgs.postgresql_12;
    ## set a custom new dataDir
    # dataDir = "/some/data/dir";
  };
  environment.systemPackages =
    let newpg = config.containers.temp-pg.config.services.postgresql;
    in [
      (pkgs.writeScriptBin "upgrade-pg-cluster" ''
        set -x
        export OLDDATA="${config.services.postgresql.dataDir}"
        export NEWDATA="${newpg.dataDir}"
        export OLDBIN="${config.services.postgresql.package}/bin"
        export NEWBIN="${newpg.package}/bin"

        install -d -m 0700 -o postgres -g postgres "$NEWDATA"
        cd "$NEWDATA"
        sudo -u postgres $NEWBIN/initdb -D "$NEWDATA"

        systemctl stop postgresql    # old one

        sudo -u postgres $NEWBIN/pg_upgrade \
          --old-datadir "$OLDDATA" --new-datadir "$NEWDATA" \
          --old-bindir $OLDBIN --new-bindir $NEWBIN \
          "$@"
      '')
    ];
</programlisting>
  </para>

  <para>
   The upgrade process is:
  </para>

  <orderedlist>
   <listitem>
    <para>
     Rebuild nixos configuration with the configuration above added to your <filename>configuration.nix</filename>. Alternatively, add that into separate file and reference it in <literal>imports</literal> list.
    </para>
   </listitem>
   <listitem>
    <para>
     Login as root (<literal>sudo su -</literal>)
    </para>
   </listitem>
   <listitem>
    <para>
     Run <literal>upgrade-pg-cluster</literal>. It will stop old postgresql, initialize new one and migrate old one to new one. You may supply arguments like <literal>--jobs 4</literal> and <literal>--link</literal> to speedup migration process. See <link xlink:href="https://www.postgresql.org/docs/current/pgupgrade.html" /> for details.
    </para>
   </listitem>
   <listitem>
    <para>
     Change postgresql package in NixOS configuration to the one you were upgrading to, and change <literal>dataDir</literal> to the one you have migrated to. Rebuild NixOS. This should start new postgres using upgraded data directory.
    </para>
   </listitem>
   <listitem>
    <para>
     After upgrade you may want to <literal>ANALYZE</literal> new db.
    </para>
   </listitem>
  </orderedlist>
 </section>
 <section xml:id="module-services-postgres-options">
  <title>Options</title>

  <para>
   A complete list of options for the PostgreSQL module may be found <link linkend="opt-services.postgresql.enable">here</link>.
  </para>
 </section>
 <section xml:id="module-services-postgres-plugins">
  <title>Plugins</title>

  <para>
   Plugins collection for each PostgreSQL version can be accessed with <literal>.pkgs</literal>. For example, for <literal>pkgs.postgresql_11</literal> package, its plugin collection is accessed by <literal>pkgs.postgresql_11.pkgs</literal>:
<screen>
<prompt>$ </prompt>nix repl '&lt;nixpkgs&gt;'

Loading '&lt;nixpkgs&gt;'...
Added 10574 variables.

<prompt>nix-repl&gt; </prompt>postgresql_11.pkgs.&lt;TAB&gt;&lt;TAB&gt;
postgresql_11.pkgs.cstore_fdw        postgresql_11.pkgs.pg_repack
postgresql_11.pkgs.pg_auto_failover  postgresql_11.pkgs.pg_safeupdate
postgresql_11.pkgs.pg_bigm           postgresql_11.pkgs.pg_similarity
postgresql_11.pkgs.pg_cron           postgresql_11.pkgs.pg_topn
postgresql_11.pkgs.pg_hll            postgresql_11.pkgs.pgjwt
postgresql_11.pkgs.pg_partman        postgresql_11.pkgs.pgroonga
...
</screen>
  </para>

  <para>
   To add plugins via NixOS configuration, set <literal>services.postgresql.extraPlugins</literal>:
<programlisting>
<xref linkend="opt-services.postgresql.package"/> = pkgs.postgresql_11;
<xref linkend="opt-services.postgresql.extraPlugins"/> = with pkgs.postgresql_11.pkgs; [
  pg_repack
  postgis
];
</programlisting>
  </para>

  <para>
   You can build custom PostgreSQL-with-plugins (to be used outside of NixOS) using function <literal>.withPackages</literal>. For example, creating a custom PostgreSQL package in an overlay can look like:
<programlisting>
self: super: {
  postgresql_custom = self.postgresql_11.withPackages (ps: [
    ps.pg_repack
    ps.postgis
  ]);
}
</programlisting>
  </para>

  <para>
   Here's a recipe on how to override a particular plugin through an overlay:
<programlisting>
self: super: {
  postgresql_11 = super.postgresql_11.override { this = self.postgresql_11; } // {
    pkgs = super.postgresql_11.pkgs // {
      pg_repack = super.postgresql_11.pkgs.pg_repack.overrideAttrs (_: {
        name = "pg_repack-v20181024";
        src = self.fetchzip {
          url = "https://github.com/reorg/pg_repack/archive/923fa2f3c709a506e111cc963034bf2fd127aa00.tar.gz";
          sha256 = "17k6hq9xaax87yz79j773qyigm4fwk8z4zh5cyp6z0sxnwfqxxw5";
        };
      });
    };
  };
}
</programlisting>
  </para>
 </section>
</chapter>