docs: Fix omissions related to configurable TOAST compression.

Previously, the default_toast_compression GUC was not documented,
and neither was pg_dump's new --no-toast-compression option.

Justin Pryzby and Robert Haas

Discussion: http://postgr.es/m/20210321235544.GD4203@telsasoft.com

doc/src/sgml/config.sgml

@@ -8108,6 +8108,28 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-default-toast-compression" xreflabel="default_toast_compression">
+      <term><varname>default_toast_compression</varname> (<type>string</type>)
+      <indexterm>
+       <primary><varname>default_toast_compression</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This variable sets the default
+        <link linkend="storage-toast">TOAST</link>
+        compression method for columns of newly-created tables. The
+        <command>CREATE TABLE</command> statement can override this default
+        by specifying the <literal>COMPRESSION</literal> column option.
+
+        The supported compression methods are <literal>pglz</literal> and
+        (if configured at the time <productname>PostgreSQL</productname> was
+        built) <literal>lz4</literal>.
+        The default is <literal>pglz</literal>.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-default-tablespace" xreflabel="default_tablespace">
       <term><varname>default_tablespace</varname> (<type>string</type>)
       <indexterm>

doc/src/sgml/ref/pg_dump.sgml

@@ -931,6 +931,18 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>--no-toast-compression</option></term>
+      <listitem>
+       <para>
+        Do not output commands to set <acronym>TOAST</acronym> compression
+        methods.
+        With this option, all objects will be created using whichever
+        compression method is the default during restore.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>--no-unlogged-table-data</option></term>
       <listitem>