Fixed bug #28571. Outer join queries with ON conditions over

constant outer tables did not return null complemented
rows when conditions were evaluated to FALSE.
Wrong results were returned because the conditions over constant
outer tables, when being pushed down, were erroneously enclosed 
into the guard function used for WHERE conditions.

mysql-test/r/join_outer.result

@@ -1239,3 +1239,18 @@ Handler_read_prev	0
 Handler_read_rnd	0
 Handler_read_rnd_next	6
 DROP TABLE t1,t2;
+CREATE TABLE t1 (c int  PRIMARY KEY, e int NOT NULL);
+INSERT INTO t1 VALUES (1,0), (2,1);
+CREATE TABLE t2 (d int PRIMARY KEY);
+INSERT INTO t2 VALUES (1), (2), (3);
+EXPLAIN SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	const	PRIMARY	PRIMARY	4	const	1	
+1	SIMPLE	t2	index	NULL	PRIMARY	4	NULL	3	Using where; Using index; Not exists
+SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d IS NULL;
+c	e	d
+1	0	NULL
+SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d<=>NULL;
+c	e	d
+1	0	NULL
+DROP TABLE t1,t2;

mysql-test/t/join_outer.test

@@ -845,3 +845,19 @@ SELECT t1.id, a FROM t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t2.b IS NULL;
 show status like 'Handler_read%';
 
 DROP TABLE t1,t2;
+
+#
+# Bug 28571: outer join with false on condition over constant tables 
+#
+
+CREATE TABLE t1 (c int  PRIMARY KEY, e int NOT NULL);
+INSERT INTO t1 VALUES (1,0), (2,1);
+CREATE TABLE t2 (d int PRIMARY KEY);
+INSERT INTO t2 VALUES (1), (2), (3);
+
+EXPLAIN SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d IS NULL;
+SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d IS NULL;
+SELECT * FROM t1 LEFT JOIN t2 ON e<>0 WHERE c=1 AND d<=>NULL;
+
+DROP TABLE t1,t2;
+

sql/sql_select.cc

@@ -5666,28 +5666,6 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *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_ref)
-          {
-            JOIN_TAB *cond_tab= tab->first_inner;
-            COND *tmp= make_cond_for_table(*tab->on_expr_ref,
-                                           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"));
@@ -5918,13 +5896,39 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
       }
       
       /* 
-        Push down all predicates from on expressions.
-        Each of these predicated are guarded by a variable
+        Push down conditions from all on expressions.
+        Each of these conditions are guarded by a variable
         that turns if off just before null complemented row for
-        outer joins is formed. Thus, the predicates from an
+        outer joins is formed. Thus, the condition from an
         'on expression' are guaranteed not to be checked for
         the null complemented row.
       */ 
+
+      /* First push down constant conditions from on expressions */
+      for (JOIN_TAB *tab= join->join_tab+join->const_tables;
+           tab < join->join_tab+join->tables ; tab++)
+      {
+        if (*tab->on_expr_ref)
+        {
+          JOIN_TAB *cond_tab= tab->first_inner;
+          COND *tmp= make_cond_for_table(*tab->on_expr_ref,
+                                         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();
+        }       
+      }
+
+      /* Push down non-constant conditions from on expressions */
       JOIN_TAB *last_tab= tab;
       while (first_inner_tab && first_inner_tab->last_inner == last_tab)
       {