join_outer.result, join_outer.test:

  Added a test case for bug #5896.
sql_select.cc:
  Fixed the problem of ignoring on expressions depending
  only on outer table when outer table either contains
  1 row or is guaranteed to return only 1 row (bug #5896).

mysql-test/r/join_outer.result

-drop table if exists t1,t2,t3,t4,t5;
+drop table if exists t0,t1,t2,t3,t4,t5;
 CREATE TABLE t1 (
 grp int(11) default NULL,
 a bigint(20) unsigned default NULL,
@@ -745,3 +745,47 @@ player_id	match_1_h	*	match_id	home	UUX
 7	4	*	1	2	2
 3	3	*	1	2	1
 drop table t1, t2;
+CREATE TABLE t0 (a0 int PRIMARY KEY);
+CREATE TABLE t1 (a1 int PRIMARY KEY);
+CREATE TABLE t2 (a2 int);
+CREATE TABLE t3 (a3 int);
+INSERT INTO t0 VALUES (1);
+INSERT INTO t1 VALUES (1);
+INSERT INTO t2 VALUES (1), (2);
+INSERT INTO t3 VALUES (1), (2);
+SELECT * FROM t1 LEFT JOIN t2 ON a1=0;
+a1	a2
+1	NULL
+EXPLAIN SELECT * FROM t1 LEFT JOIN t2 ON a1=0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
+SELECT * FROM t1 LEFT JOIN (t2,t3) ON a1=0;
+a1	a2	a3
+1	NULL	NULL
+EXPLAIN SELECT * FROM t1 LEFT JOIN (t2,t3) ON a1=0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
+1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	2	
+SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=0 WHERE a0=a1;
+a0	a1	a2	a3
+1	1	NULL	NULL
+EXPLAIN SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=0 WHERE a0=a1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	system	PRIMARY	NULL	NULL	NULL	1	
+1	SIMPLE	t1	system	PRIMARY	NULL	NULL	NULL	1	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
+1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	2	
+INSERT INTO t0 VALUES (0);
+INSERT INTO t1 VALUES (0);
+SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=5 WHERE a0=a1 AND a0=1;
+a0	a1	a2	a3
+1	1	NULL	NULL
+EXPLAIN SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=5 WHERE a0=a1 AND a0=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	const	PRIMARY	PRIMARY	4	const	1	Using index
+1	SIMPLE	t1	const	PRIMARY	PRIMARY	4	const	1	Using index
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
+1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	2	
+DROP TABLE t0,t1,t2,t3;

mysql-test/t/join_outer.test

@@ -3,7 +3,7 @@
 #
 
 --disable_warnings
-drop table if exists t1,t2,t3,t4,t5;
+drop table if exists t0,t1,t2,t3,t4,t5;
 --enable_warnings
 
 CREATE TABLE t1 (
@@ -501,3 +501,28 @@ select s.*, '*', m.*, (s.match_1_h - m.home) UUX from
   order by UUX desc;
 
 drop table t1, t2;
+
+# Test for bug #5896  
+
+CREATE TABLE t0 (a0 int PRIMARY KEY);
+CREATE TABLE t1 (a1 int PRIMARY KEY);
+CREATE TABLE t2 (a2 int);
+CREATE TABLE t3 (a3 int);
+INSERT INTO t0 VALUES (1);
+INSERT INTO t1 VALUES (1);
+INSERT INTO t2 VALUES (1), (2);
+INSERT INTO t3 VALUES (1), (2);
+
+SELECT * FROM t1 LEFT JOIN t2 ON a1=0;
+EXPLAIN SELECT * FROM t1 LEFT JOIN t2 ON a1=0;
+SELECT * FROM t1 LEFT JOIN (t2,t3) ON a1=0;
+EXPLAIN SELECT * FROM t1 LEFT JOIN (t2,t3) ON a1=0;
+SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=0 WHERE a0=a1;
+EXPLAIN SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=0 WHERE a0=a1;
+
+INSERT INTO t0 VALUES (0);
+INSERT INTO t1 VALUES (0);
+SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=5 WHERE a0=a1 AND a0=1;
+EXPLAIN SELECT * FROM t0, t1 LEFT JOIN (t2,t3) ON a1=5 WHERE a0=a1 AND a0=1;
+
+DROP TABLE t0,t1,t2,t3;

sql/sql_select.cc

@@ -4895,6 +4895,28 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
       COND *const_cond=
 	make_cond_for_table(cond,join->const_table_map,(table_map) 0);
       DBUG_EXECUTE("where",print_where(const_cond,"constants"););
+      for (JOIN_TAB *tab= join->join_tab+join->const_tables;
+           tab < join->join_tab+join->tables ; tab++)
+      {
+        if (tab->on_expr)
+        {
+          JOIN_TAB *cond_tab= tab->first_inner;
+          COND *tmp= make_cond_for_table(tab->on_expr,
+                                         join->const_table_map,
+                                         (table_map) 0);
+          if (!tmp)
+            continue;
+          tmp= new Item_func_trig_cond(tmp, &cond_tab->not_null_compl);
+          if (!tmp)
+            DBUG_RETURN(1);
+          tmp->quick_fix_field();
+          cond_tab->select_cond= !cond_tab->select_cond ? tmp :
+	                          new Item_cond_and(cond_tab->select_cond,tmp);
+          if (!cond_tab->select_cond)
+	    DBUG_RETURN(1);
+          cond_tab->select_cond->quick_fix_field();
+        }       
+      }
       if (const_cond && !const_cond->val_int())
       {
 	DBUG_PRINT("info",("Found impossible WHERE condition"));