From 3cf0d6f446b51b76a53378a11a117a134158f407 Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Thu, 23 Jun 2011 14:48:45 -0700
Subject: [PATCH] Fixed LP bug #800518. The function simple_pred did not take
 into account that a multiple equality could include ref items (more exactly
 items of the class Item_direct_view_ref). It caused crashes for queries over
 derived tables or views if the min/max optimization could be applied to these
 queries.

---
 mysql-test/r/derived.result | 16 ++++++++++++++++
 mysql-test/t/derived.test   | 17 +++++++++++++++++
 sql/opt_sum.cc              | 10 ++++++----
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/mysql-test/r/derived.result b/mysql-test/r/derived.result
index fe803ed37a5..0340ebcbe98 100644
--- a/mysql-test/r/derived.result
+++ b/mysql-test/r/derived.result
@@ -425,3 +425,19 @@ SELECT * FROM (SELECT DISTINCT * FROM t2) t, t1  WHERE t1.a = t.a;
 a	a
 3	3
 DROP TABLE t1,t2;
+#
+#  LP bug #800518: crash with a query over a derived table
+#                  when a min/max optimization is applied
+#
+CREATE TABLE t1 (a int, b int, c varchar(10), INDEX idx(a,b)) ;
+INSERT INTO t1 VALUES 
+(100, 3, 'xxx'), (200, 7, 'yyyyyyy'), (100, 1, 't'),
+(200, 4, 'aaaa'), (100, 3, 'eee'), (100, 5, 'zzzzz');
+EXPLAIN
+SELECT MAX(b) FROM (SELECT * FROM t1) AS t WHERE a = 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+SELECT MAX(b) FROM (SELECT * FROM t1) AS t WHERE a = 100;
+MAX(b)
+5
+DROP TABLE t1;
diff --git a/mysql-test/t/derived.test b/mysql-test/t/derived.test
index 75368925499..4bba495ca09 100644
--- a/mysql-test/t/derived.test
+++ b/mysql-test/t/derived.test
@@ -331,3 +331,20 @@ SELECT * FROM (SELECT DISTINCT * FROM t2) t, t1  WHERE t1.a = t.a;
 SELECT * FROM (SELECT DISTINCT * FROM t2) t, t1  WHERE t1.a = t.a;
 
 DROP TABLE t1,t2;
+
+--echo #
+--echo #  LP bug #800518: crash with a query over a derived table
+--echo #                  when a min/max optimization is applied
+--echo #
+
+CREATE TABLE t1 (a int, b int, c varchar(10), INDEX idx(a,b)) ;
+INSERT INTO t1 VALUES 
+  (100, 3, 'xxx'), (200, 7, 'yyyyyyy'), (100, 1, 't'),
+  (200, 4, 'aaaa'), (100, 3, 'eee'), (100, 5, 'zzzzz');
+
+EXPLAIN
+SELECT MAX(b) FROM (SELECT * FROM t1) AS t WHERE a = 100;
+SELECT MAX(b) FROM (SELECT * FROM t1) AS t WHERE a = 100;
+
+DROP TABLE t1;
+
diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc
index 965eb853471..78cb2fa8210 100644
--- a/sql/opt_sum.cc
+++ b/sql/opt_sum.cc
@@ -494,12 +494,14 @@ bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
     /* MULT_EQUAL_FUNC */
     {
       Item_equal *item_equal= (Item_equal *) func_item;
-      Item_equal_fields_iterator it(*item_equal);
-      args[0]= it++;
-      if (it++)
-        return 0;
       if (!(args[1]= item_equal->get_const()))
         return 0;
+      Item_equal_fields_iterator it(*item_equal);
+      if (!(item= it++))
+        return 0;
+      args[0]= item->real_item();
+      if (it++)
+        return 0;
     }
     break;
   case 1: