232 lines
8.3 KiB
XML
232 lines
8.3 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="module-postgresql">
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<title>PostgreSQL</title>
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<!-- FIXME: render nicely -->
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<!-- FIXME: source can be added automatically -->
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<para>
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<emphasis>Source:</emphasis> <filename>modules/services/databases/postgresql.nix</filename>
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</para>
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<para>
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<emphasis>Upstream documentation:</emphasis> <link xlink:href="http://www.postgresql.org/docs/"/>
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</para>
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<!-- FIXME: more stuff, like maintainer? -->
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<para>
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PostgreSQL is an advanced, free relational database.
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<!-- MORE -->
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</para>
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<section xml:id="module-services-postgres-configuring">
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<title>Configuring</title>
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<para>
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To enable PostgreSQL, add the following to your <filename>configuration.nix</filename>:
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<programlisting>
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<xref linkend="opt-services.postgresql.enable"/> = true;
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<xref linkend="opt-services.postgresql.package"/> = pkgs.postgresql_11;
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</programlisting>
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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.
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</para>
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<!--
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<para>After running <command>nixos-rebuild</command>, you can verify
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whether PostgreSQL works by running <command>psql</command>:
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<screen>
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<prompt>$ </prompt>psql
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psql (9.2.9)
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Type "help" for help.
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<prompt>alice=></prompt>
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</screen>
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-->
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<para>
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By default, PostgreSQL stores its databases in <filename>/var/lib/postgresql/$psqlSchema</filename>. You can override this using <xref linkend="opt-services.postgresql.dataDir"/>, e.g.
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<programlisting>
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<xref linkend="opt-services.postgresql.dataDir"/> = "/data/postgresql";
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</programlisting>
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</para>
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</section>
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<section xml:id="module-services-postgres-upgrading">
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<title>Upgrading</title>
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<note>
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<para>
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The steps below demonstrate how to upgrade from an older version to <package>pkgs.postgresql_13</package>.
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These instructions are also applicable to other versions.
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</para>
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</note>
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<para>
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Major PostgreSQL upgrades require a downtime and a few imperative steps to be called. This is the case because
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each major version has some internal changes in the databases' state during major releases. Because of that,
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NixOS places the state into <filename>/var/lib/postgresql/<version></filename> where each <literal>version</literal>
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can be obtained like this:
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<programlisting>
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<prompt>$ </prompt>nix-instantiate --eval -A postgresql_13.psqlSchema
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"13"
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</programlisting>
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For an upgrade, a script like this can be used to simplify the process:
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<programlisting>
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{ config, pkgs, ... }:
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{
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<xref linkend="opt-environment.systemPackages" /> = [
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(let
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# XXX specify the postgresql package you'd like to upgrade to.
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# Do not forget to list the extensions you need.
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newPostgres = pkgs.postgresql_13.withPackages (pp: [
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# pp.plv8
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]);
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in pkgs.writeScriptBin "upgrade-pg-cluster" ''
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set -eux
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# XXX it's perhaps advisable to stop all services that depend on postgresql
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systemctl stop postgresql
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export NEWDATA="/var/lib/postgresql/${newPostgres.psqlSchema}"
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export NEWBIN="${newPostgres}/bin"
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export OLDDATA="${config.<xref linkend="opt-services.postgresql.dataDir"/>}"
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export OLDBIN="${config.<xref linkend="opt-services.postgresql.package"/>}/bin"
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install -d -m 0700 -o postgres -g postgres "$NEWDATA"
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cd "$NEWDATA"
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sudo -u postgres $NEWBIN/initdb -D "$NEWDATA"
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sudo -u postgres $NEWBIN/pg_upgrade \
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--old-datadir "$OLDDATA" --new-datadir "$NEWDATA" \
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--old-bindir $OLDBIN --new-bindir $NEWBIN \
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"$@"
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'')
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];
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}
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</programlisting>
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</para>
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<para>
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The upgrade process is:
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</para>
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<orderedlist>
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<listitem>
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<para>
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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.
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</para>
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</listitem>
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<listitem>
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<para>
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Login as root (<literal>sudo su -</literal>)
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</para>
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</listitem>
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<listitem>
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<para>
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Run <literal>upgrade-pg-cluster</literal>. It will stop old postgresql, initialize a new one and migrate the old one to the 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.
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</para>
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</listitem>
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<listitem>
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<para>
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Change postgresql package in NixOS configuration to the one you were upgrading to via <xref linkend="opt-services.postgresql.package" />. Rebuild NixOS. This should start new postgres using upgraded data directory and all services you stopped during the upgrade.
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</para>
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</listitem>
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<listitem>
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<para>
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After the upgrade it's advisable to analyze the new cluster.
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</para>
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<itemizedlist>
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<listitem>
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<para>
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For PostgreSQL ≥ 14, use the <literal>vacuumdb</literal> command printed by the upgrades script.
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</para>
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</listitem>
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<listitem>
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<para>
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For PostgreSQL < 14, run (as <literal>su -l postgres</literal> in the <xref linkend="opt-services.postgresql.dataDir" />, in this example <filename>/var/lib/postgresql/13</filename>):
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<programlisting>
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<prompt>$ </prompt>./analyze_new_cluster.sh
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</programlisting>
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</para>
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</listitem>
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</itemizedlist>
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<para>
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<warning><para>The next step removes the old state-directory!</para></warning>
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<programlisting>
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<prompt>$ </prompt>./delete_old_cluster.sh
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</programlisting>
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</para>
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</listitem>
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</orderedlist>
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</section>
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<section xml:id="module-services-postgres-options">
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<title>Options</title>
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<para>
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A complete list of options for the PostgreSQL module may be found <link linkend="opt-services.postgresql.enable">here</link>.
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</para>
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</section>
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<section xml:id="module-services-postgres-plugins">
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<title>Plugins</title>
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<para>
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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>:
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<screen>
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<prompt>$ </prompt>nix repl '<nixpkgs>'
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Loading '<nixpkgs>'...
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Added 10574 variables.
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<prompt>nix-repl> </prompt>postgresql_11.pkgs.<TAB><TAB>
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postgresql_11.pkgs.cstore_fdw postgresql_11.pkgs.pg_repack
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postgresql_11.pkgs.pg_auto_failover postgresql_11.pkgs.pg_safeupdate
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postgresql_11.pkgs.pg_bigm postgresql_11.pkgs.pg_similarity
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postgresql_11.pkgs.pg_cron postgresql_11.pkgs.pg_topn
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postgresql_11.pkgs.pg_hll postgresql_11.pkgs.pgjwt
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postgresql_11.pkgs.pg_partman postgresql_11.pkgs.pgroonga
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...
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</screen>
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</para>
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<para>
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To add plugins via NixOS configuration, set <literal>services.postgresql.extraPlugins</literal>:
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<programlisting>
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<xref linkend="opt-services.postgresql.package"/> = pkgs.postgresql_11;
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<xref linkend="opt-services.postgresql.extraPlugins"/> = with pkgs.postgresql_11.pkgs; [
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pg_repack
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postgis
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];
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</programlisting>
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</para>
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<para>
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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:
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<programlisting>
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self: super: {
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postgresql_custom = self.postgresql_11.withPackages (ps: [
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ps.pg_repack
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ps.postgis
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]);
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}
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</programlisting>
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</para>
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<para>
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Here's a recipe on how to override a particular plugin through an overlay:
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<programlisting>
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self: super: {
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postgresql_11 = super.postgresql_11.override { this = self.postgresql_11; } // {
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pkgs = super.postgresql_11.pkgs // {
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pg_repack = super.postgresql_11.pkgs.pg_repack.overrideAttrs (_: {
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name = "pg_repack-v20181024";
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src = self.fetchzip {
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url = "https://github.com/reorg/pg_repack/archive/923fa2f3c709a506e111cc963034bf2fd127aa00.tar.gz";
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sha256 = "17k6hq9xaax87yz79j773qyigm4fwk8z4zh5cyp6z0sxnwfqxxw5";
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};
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});
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};
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};
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}
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</programlisting>
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</para>
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</section>
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</chapter>
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