Clarify documentation on the behavior of unnamed bind queries.

doc/src/sgml/protocol.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.78 2010/02/03 09:47:19 heikki Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.79 2010/02/16 20:15:14 momjian Exp $ -->
 
 <chapter id="protocol">
  <title>Frontend/Backend Protocol</title>
@@ -737,9 +737,9 @@
    <para>
     The unnamed prepared statement is likewise planned during Parse processing
     if the Parse message defines no parameters.  But if there are parameters,
-    query planning occurs during Bind processing instead.  This allows the
-    planner to make use of the actual values of the parameters provided in
-    the Bind message when planning the query.
+    query planning occurs every time Bind parameters are supplied.  This allows the
+    planner to make use of the actual values of the parameters provided by
+    each Bind message, rather than use generic estimates.
    </para>
 
    <note>

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.588 2010/02/13 01:32:19 sriggs Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.589 2010/02/16 20:15:14 momjian Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -1469,7 +1469,7 @@ exec_bind_message(StringInfo input_message)
 	}
 	else
 	{
-		/* special-case the unnamed statement */
+		/* Unnamed statements are re-prepared for every bind */
 		psrc = unnamed_stmt_psrc;
 		if (!psrc)
 			ereport(ERROR,