Merge

mysql-test/r/join_outer.result

@@ -1397,4 +1397,18 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select straight_join `test`.`jt1`.`f1` AS `f1` from `test`.`t1` `jt6` left join (`test`.`t1` `jt3` join `test`.`t1` `jt4` left join `test`.`t1` `jt5` on(1) left join `test`.`t1` `jt2` on(1)) on((`test`.`jt6`.`f1` and 1)) left join `test`.`t1` `jt1` on(1) where 1
 DROP TABLE t1;
+#
+# Bug#49600: outer join of two single-row tables with joining attributes
+#            evaluated to nulls
+create table t1 (a int, b int);
+create table t2 (a int, b int);
+insert into t1 values (1, NULL);
+insert into t2 values (2, NULL);
+select * from t1 left join t2 on t1.b=t2.b;
+a	b	a	b
+1	NULL	NULL	NULL
+select * from t1 left join t2 on t1.b=t2.b where 1=1;
+a	b	a	b
+1	NULL	NULL	NULL
+drop table t1,t2;
 End of 5.1 tests

mysql-test/r/table_elim.result

@@ -60,7 +60,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	4	100.00	
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	100.00	
 Warnings:
-Note	1003	select `test`.`t0`.`a` AS `a` from `test`.`t0` left join (`test`.`t1`) on((`test`.`t0`.`a` = `test`.`t1`.`a`)) where 1
+Note	1003	select `test`.`t0`.`a` AS `a` from `test`.`t0` left join (`test`.`t1`) on((`test`.`t1`.`a` = `test`.`t0`.`a`)) where 1
 # Elimination with aggregate functions
 explain select count(*) from t1 left join t2 on t2.a=t1.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/view.result

@@ -1418,7 +1418,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 Warnings:
-Note	1003	select `test`.`t3`.`a` AS `a`,`test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `b` from `test`.`t3` left join (`test`.`t1` left join `test`.`t2` on((`test`.`t1`.`a` = `test`.`t2`.`a`))) on((`test`.`t3`.`a` = `test`.`t1`.`a`)) where 1
+Note	1003	select `test`.`t3`.`a` AS `a`,`test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `b` from `test`.`t3` left join (`test`.`t1` left join `test`.`t2` on(((`test`.`t1`.`a` = `test`.`t3`.`a`) and (`test`.`t2`.`a` = `test`.`t3`.`a`)))) on((`test`.`t1`.`a` = `test`.`t3`.`a`)) where 1
 create view v1 (a) as select a from t1;
 create view v2 (a) as select a from t2;
 create view v4 (a,b) as select v1.a as a, v2.a as b from v1 left join v2 on (v1.a=v2.a);
@@ -1433,7 +1433,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 Warnings:
-Note	1003	select `test`.`t3`.`a` AS `a`,`test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `b` from `test`.`t3` left join (`test`.`t1` left join (`test`.`t2`) on((`test`.`t1`.`a` = `test`.`t2`.`a`))) on((`test`.`t3`.`a` = `test`.`t1`.`a`)) where 1
+Note	1003	select `test`.`t3`.`a` AS `a`,`test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `b` from `test`.`t3` left join (`test`.`t1` left join (`test`.`t2`) on(((`test`.`t1`.`a` = `test`.`t3`.`a`) and (`test`.`t2`.`a` = `test`.`t3`.`a`)))) on((`test`.`t1`.`a` = `test`.`t3`.`a`)) where 1
 prepare stmt1 from "select * from t3 left join v4 on (t3.a = v4.a);";
 execute stmt1;
 a	a	b

mysql-test/t/join_outer.test

@@ -981,4 +981,19 @@ EXPLAIN EXTENDED SELECT STRAIGHT_JOIN jt1.f1 FROM t1 AS jt1
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#49600: outer join of two single-row tables with joining attributes
+--echo #            evaluated to nulls
+
+create table t1 (a int, b int);
+create table t2 (a int, b int);
+insert into t1 values (1, NULL);
+insert into t2 values (2, NULL);
+
+select * from t1 left join t2 on t1.b=t2.b;
+
+select * from t1 left join t2 on t1.b=t2.b where 1=1;
+
+drop table t1,t2;
+
 --echo End of 5.1 tests

sql/item_cmpfunc.cc

@@ -5507,7 +5507,7 @@ longlong Item_equal::val_int()
     return 0;
   List_iterator_fast<Item_field> it(fields);
   Item *item= const_item ? const_item : it++;
-  if ((null_value= item->null_value))
+  if ((null_value= item->is_null()))
     return 0;
   eval_item->store_value(item);
   while ((item_field= it++))
@@ -5515,7 +5515,7 @@ longlong Item_equal::val_int()
     /* Skip fields of non-const tables. They haven't been read yet */
     if (item_field->field->table->const_table)
     {
-      if ((null_value= item_field->null_value) || eval_item->cmp(item_field))
+      if ((null_value= item_field->is_null()) || eval_item->cmp(item_field))
         return 0;
     }
   }

sql/sql_select.cc

@@ -9315,7 +9315,10 @@ optimize_cond(JOIN *join, COND *conds, List<TABLE_LIST> *join_list,
   DBUG_ENTER("optimize_cond");
 
   if (!conds)
+  {
     *cond_value= Item::COND_TRUE;
+    build_equal_items(join->thd, NULL, NULL, join_list, &join->cond_equal);
+  }  
   else
   {
     /*