From aaf9fb0de706da2924bdcb2533b1eda6933aca61 Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Tue, 3 May 2011 17:11:45 -0700
Subject: [PATCH] Fixed LP bug #776274, The bug was introduced by the patch
 that fixed bug 717577.

---
 mysql-test/r/select.result           | 13 +++++++++++++
 mysql-test/r/select_jcl6.result      | 13 +++++++++++++
 mysql-test/r/select_pkeycache.result | 13 +++++++++++++
 mysql-test/t/select.test             | 14 ++++++++++++++
 sql/item_cmpfunc.cc                  | 19 ++++++++++---------
 5 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/mysql-test/r/select.result b/mysql-test/r/select.result
index 56d383a57b7..f9d6c80018b 100644
--- a/mysql-test/r/select.result
+++ b/mysql-test/r/select.result
@@ -5018,3 +5018,16 @@ WHERE t7.f71>0;
 f23
 DROP TABLE t1,t2,t3,t4,t5,t6,t7;
 End of 5.1 tests
+#
+# BUG#776274: substitution of a single row table
+#                    
+CREATE TABLE t1 (a int NOT NULL , b int);
+INSERT INTO t1 VALUES (2,2);
+SELECT * FROM t1 WHERE a = b;
+a	b
+2	2
+EXPLAIN
+SELECT * FROM t1 WHERE a = b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+DROP TABLE t1;
diff --git a/mysql-test/r/select_jcl6.result b/mysql-test/r/select_jcl6.result
index caa0fcb5cf6..ca7241d8f87 100644
--- a/mysql-test/r/select_jcl6.result
+++ b/mysql-test/r/select_jcl6.result
@@ -5025,6 +5025,19 @@ WHERE t7.f71>0;
 f23
 DROP TABLE t1,t2,t3,t4,t5,t6,t7;
 End of 5.1 tests
+#
+# BUG#776274: substitution of a single row table
+#                    
+CREATE TABLE t1 (a int NOT NULL , b int);
+INSERT INTO t1 VALUES (2,2);
+SELECT * FROM t1 WHERE a = b;
+a	b
+2	2
+EXPLAIN
+SELECT * FROM t1 WHERE a = b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+DROP TABLE t1;
 set join_cache_level=default;
 show variables like 'join_cache_level';
 Variable_name	Value
diff --git a/mysql-test/r/select_pkeycache.result b/mysql-test/r/select_pkeycache.result
index 56d383a57b7..f9d6c80018b 100644
--- a/mysql-test/r/select_pkeycache.result
+++ b/mysql-test/r/select_pkeycache.result
@@ -5018,3 +5018,16 @@ WHERE t7.f71>0;
 f23
 DROP TABLE t1,t2,t3,t4,t5,t6,t7;
 End of 5.1 tests
+#
+# BUG#776274: substitution of a single row table
+#                    
+CREATE TABLE t1 (a int NOT NULL , b int);
+INSERT INTO t1 VALUES (2,2);
+SELECT * FROM t1 WHERE a = b;
+a	b
+2	2
+EXPLAIN
+SELECT * FROM t1 WHERE a = b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+DROP TABLE t1;
diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index fb04562a173..3d5ffd185ba 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -4211,3 +4211,17 @@ SELECT t2.f23 FROM
 DROP TABLE t1,t2,t3,t4,t5,t6,t7;
 
 --echo End of 5.1 tests
+
+--echo #
+--echo # BUG#776274: substitution of a single row table
+--echo #                    
+
+CREATE TABLE t1 (a int NOT NULL , b int);
+INSERT INTO t1 VALUES (2,2);
+
+SELECT * FROM t1 WHERE a = b;
+EXPLAIN
+SELECT * FROM t1 WHERE a = b;
+
+DROP TABLE t1;
+
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index cc6f2f41982..73191982b64 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -5740,18 +5740,19 @@ void Item_equal::update_const()
   List_iterator<Item> it(equal_items);
   if (with_const)
     it++;
-  Item *item= it++;
-  while (item)
+  Item *item;
+  while ((item= it++))
   {
     if (item->const_item())
     {
-      it.remove();
-      Item *next_item= it++;
-      add_const(item);
-      item= next_item;
-    }
-    else
-      item= it++;
+      if (item == equal_items.head())
+        with_const= TRUE;
+      else
+      {
+        it.remove();
+        add_const(item);
+      }
+    } 
   }
 }