Revert thinko introduced into prefix_selectivity() by my recent patch:

make_greater_string needs the < procedure not the >= one.  Spotted by
Peter.

src/backend/utils/adt/selfuncs.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.245 2008/03/09 00:32:09 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.246 2008/03/17 17:13:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4531,17 +4531,17 @@ prefix_selectivity(VariableStatData *vardata,
 	 *	"x < greaterstr".
 	 *-------
 	 */
+	cmpopr = get_opfamily_member(opfamily, vartype, vartype,
+								 BTLessStrategyNumber);
+	if (cmpopr == InvalidOid)
+		elog(ERROR, "no < operator for opfamily %u", opfamily);
+	fmgr_info(get_opcode(cmpopr), &opproc);
+
 	greaterstrcon = make_greater_string(prefixcon, &opproc);
 	if (greaterstrcon)
 	{
 		Selectivity topsel;
 
-		cmpopr = get_opfamily_member(opfamily, vartype, vartype,
-									 BTLessStrategyNumber);
-		if (cmpopr == InvalidOid)
-			elog(ERROR, "no < operator for opfamily %u", opfamily);
-		fmgr_info(get_opcode(cmpopr), &opproc);
-
 		topsel = ineq_histogram_selectivity(vardata, &opproc, false,
 											greaterstrcon->constvalue,
 											greaterstrcon->consttype);