fixed subselect explain bug

mysql-test/r/subselect.result

@@ -269,3 +269,21 @@ INSERT INTO iftest VALUES ();
 SELECT field FROM iftest WHERE 1=(SELECT 1 UNION ALL SELECT 1 FROM (SELECT 1) HAVING field='b');
 Subselect returns more than 1 record
 drop table iftest;
+drop table if exists threadhardwarefr7;
+CREATE TABLE `threadhardwarefr7` (
+`numeropost` mediumint(8) unsigned NOT NULL default '0',
+`numreponse` int(10) unsigned NOT NULL auto_increment,
+`pseudo` varchar(35) NOT NULL default '',
+PRIMARY KEY  (`numeropost`,`numreponse`),
+UNIQUE KEY `numreponse` (`numreponse`),
+KEY `pseudo` (`pseudo`,`numeropost`)
+) TYPE=MyISAM;
+INSERT INTO threadhardwarefr7 (numeropost,numreponse,pseudo) VALUES (1,1,'joce'),(1,2,'joce'),(1,3,'test');
+EXPLAIN SELECT MAX(numreponse) FROM threadhardwarefr7 WHERE numeropost='1';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE								Select tables optimized away
+EXPLAIN SELECT numreponse FROM threadhardwarefr7 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM threadhardwarefr7 WHERE numeropost='1');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	threadhardwarefr7	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	
+2	SUBSELECT								Select tables optimized away
+drop table if exists threadhardwarefrtest7;

mysql-test/t/subselect.test

@@ -166,3 +166,18 @@ INSERT INTO iftest VALUES ();
 -- error 1240
 SELECT field FROM iftest WHERE 1=(SELECT 1 UNION ALL SELECT 1 FROM (SELECT 1) HAVING field='b');
 drop table iftest;
+
+drop table if exists threadhardwarefr7;
+CREATE TABLE `threadhardwarefr7` (
+  `numeropost` mediumint(8) unsigned NOT NULL default '0',
+  `numreponse` int(10) unsigned NOT NULL auto_increment,
+  `pseudo` varchar(35) NOT NULL default '',
+  PRIMARY KEY  (`numeropost`,`numreponse`),
+  UNIQUE KEY `numreponse` (`numreponse`),
+  KEY `pseudo` (`pseudo`,`numeropost`)
+) TYPE=MyISAM;
+INSERT INTO threadhardwarefr7 (numeropost,numreponse,pseudo) VALUES (1,1,'joce'),(1,2,'joce'),(1,3,'test');
+
+EXPLAIN SELECT MAX(numreponse) FROM threadhardwarefr7 WHERE numeropost='1';
+EXPLAIN SELECT numreponse FROM threadhardwarefr7 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM threadhardwarefr7 WHERE numeropost='1');
+drop table if exists threadhardwarefrtest7;

sql/sql_select.cc

@@ -395,13 +395,7 @@ JOIN::optimize()
 	zero_result_cause= "No matching min/max row";
 	DBUG_RETURN(0);
       }
-      if (select_options & SELECT_DESCRIBE)
-      {
-	select_describe(this, false, false, false,
-			"Select tables optimized away");
-	delete procedure;
-	DBUG_RETURN(1);
-      }
+      zero_result_cause= "Select tables optimized away";
       tables_list= 0;					// All tables resolved
     }
   }
@@ -663,7 +657,8 @@ JOIN::exec()
   {                                           // Only test of functions
     error=0;
     if (select_options & SELECT_DESCRIBE)
-      select_describe(this, false, false, false, "No tables used");
+      select_describe(this, false, false, false,
+		      (zero_result_cause?zero_result_cause:"No tables used"));
     else
     {
       result->send_fields(fields_list,1);