Add libpq comment about how to determine the format used for passing

binary values.

Add comments to libpq C function for parameter passing.

doc/src/sgml/libpq.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.258 2008/06/01 16:23:08 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.259 2008/06/23 21:10:49 momjian Exp $ -->
 
 <chapter id="libpq">
  <title><application>libpq</application> - C Library</title>
@@ -1397,6 +1397,14 @@ PGresult *PQexecParams(PGconn *conn,
             If the array pointer is null then all parameters are presumed
             to be text strings.
            </para>
+           <para>
+            Values passed in binary format require knowlege of
+            the internal representation expected by the backend.
+            For example, integers must be passed in network byte
+            order.  Passing <type>numeric</> values requires
+            knowledge of the server storage format, as implemented
+            in <filename>src/backend/utils/adt/numeric.c</>.
+           </para>
           </listitem>
          </varlistentry>
 

src/interfaces/libpq/fe-exec.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.195 2008/05/29 22:02:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.196 2008/06/23 21:10:49 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -976,12 +976,13 @@ PQsendQueryGuts(PGconn *conn,
 			goto sendFailed;
 	}
 
-	/* construct the Bind message */
+	/* Construct the Bind message */
 	if (pqPutMsgStart('B', false, conn) < 0 ||
 		pqPuts("", conn) < 0 ||
 		pqPuts(stmtName, conn) < 0)
 		goto sendFailed;
 
+	/* Send parameter formats */
 	if (nParams > 0 && paramFormats)
 	{
 		if (pqPutInt(nParams, 2, conn) < 0)
@@ -1001,6 +1002,7 @@ PQsendQueryGuts(PGconn *conn,
 	if (pqPutInt(nParams, 2, conn) < 0)
 		goto sendFailed;
 
+	/* Send parameters */
 	for (i = 0; i < nParams; i++)
 	{
 		if (paramValues && paramValues[i])