Add extra_float_digits GUC parameter to allow adjustment of displayed

precision for float4, float8, and geometric types.  Set it in pg_dump
so that float data can be dumped/reloaded exactly (at least on platforms
where the float I/O support is properly implemented).  Initial patch by
Pedro Ferreira, some additional work by Tom Lane.

doc/src/sgml/runtime.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.148 2002/11/05 23:16:56 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.149 2002/11/08 17:37:52 tgl Exp $
 -->
 
 <Chapter Id="runtime">
@@ -1448,6 +1448,30 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <indexterm>
+       <primary>significant digits</primary>
+      </indexterm>
+      <indexterm>
+       <primary>display</primary>
+       <secondary>of float numbers</secondary>
+      </indexterm>
+
+      <term><varname>EXTRA_FLOAT_DIGITS</varname> (<type>integer</type>)</term>
+      <listitem>
+       <para>
+        This parameter adjusts the number of digits displayed for
+	floating-point values, including <type>float4</>, <type>float8</>,
+	and geometric datatypes.  The parameter value is added to the
+	standard number of digits (<literal>FLT_DIG</> or <literal>DBL_DIG</>
+	as appropriate).  The value can be set as high as 2, to include
+	partially-significant digits; this is especially useful for dumping
+	float data that needs to be restored exactly.  Or it can be set
+	negative to suppress unwanted digits.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><varname>KRB_SERVER_KEYFILE</varname> (<type>string</type>)</term>
       <listitem>