Add libpq connection option to disable SSL compression

This can be used to remove the overhead of SSL compression on
fast networks.

Laurenz Albe

doc/src/sgml/libpq.sgml

@@ -494,6 +494,28 @@ PGconn *PQconnectdbParams(const char * const *keywords,
          </listitem>
         </varlistentry>
 
+        <varlistentry id="libpq-connect-sslcompression" xreflabel="sslcompression">
+         <term><literal>sslcompression</literal></term>
+         <listitem>
+          <para>
+           If set to 1 (default), data sent over SSL connections will be
+           compressed (this requires <productname>OpenSSL</> version
+           0.9.8 or later).
+           If set to 0, compression will be disabled (this requires
+           <productname>OpenSSL</> 1.0.0 or later).
+           This parameter is ignored if a connection without SSL is made,
+           or if the version of <productname>OpenSSL</> used does not support
+           it.
+          </para>
+          <para>
+           Compression uses CPU time, but can improve throughput if
+           the network is the bottleneck.
+           Disabling compression can improve response time and throughput
+           if CPU performance is the limiting factor.
+          </para>
+         </listitem>
+        </varlistentry>
+
         <varlistentry id="libpq-connect-sslcert" xreflabel="sslcert">
          <term><literal>sslcert</literal></term>
          <listitem>
@@ -6308,6 +6330,16 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      <indexterm>
+       <primary><envar>PGSSLCOMPRESSION</envar></primary>
+      </indexterm>
+      <envar>PGSSLCOMPRESSION</envar> behaves the same as the <xref
+      linkend="libpq-connect-sslcompression"> connection parameter.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       <indexterm>