Fixed LP bug #817360.

This problem could be observed for queries with nested outer joins
for which the not_exist optimization were applicable. 
The problem was caused by the code of the patch for bug #49322
that erroneously forced the return to the previous nested loop
level when the join algorithm successfully builds a partial record
for an embedded outer to which the not_exist optimization could be
applied.
Actually the immediate return to the previous nested loops level
is correct only if this partial record is rejected by a predicate
pushed down to one of the inner tables of this outer join. Otherwise
attempts to find extensions of this record must be made.

mysql-test/r/join_nested.result

@@ -1801,4 +1801,35 @@ pk	a	pk	a	pk	a
 7	NULL	NULL	NULL	NULL	NULL
 8	9	NULL	NULL	NULL	NULL
 DROP TABLE t1, t2, t3;
+CREATE TABLE t1 (a int NOT NULL );
+INSERT INTO t1 VALUES (9), (9);
+CREATE TABLE t2 (a int NOT NULL );
+INSERT INTO t2 VALUES (9);
+CREATE TABLE t3 (a int NOT NULL, b int);
+INSERT INTO t3 VALUES (19,9);
+CREATE TABLE t4 (b int) ;
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a;
+a	a	a	b	b
+9	9	19	9	NULL
+9	9	19	9	NULL
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a
+WHERE t3.a IS NULL;
+a	a	a	b	b
+EXPLAIN EXTENDED
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a
+WHERE t3.a IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where
+1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where; Not exists
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	0	0.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`b` AS `b` from `test`.`t1` left join (`test`.`t2` left join `test`.`t3` on(((`test`.`t2`.`a` = `test`.`t1`.`a`) and (`test`.`t3`.`b` = `test`.`t1`.`a`))) left join `test`.`t4` on((`test`.`t4`.`b` = `test`.`t3`.`a`))) on((`test`.`t2`.`a` = `test`.`t1`.`a`)) where isnull(`test`.`t3`.`a`)
+DROP TABLE t1,t2,t3,t4;
 End of 5.0 tests

mysql-test/r/join_nested_jcl6.result

@@ -1810,6 +1810,37 @@ pk	a	pk	a	pk	a
 7	NULL	NULL	NULL	NULL	NULL
 8	9	NULL	NULL	NULL	NULL
 DROP TABLE t1, t2, t3;
+CREATE TABLE t1 (a int NOT NULL );
+INSERT INTO t1 VALUES (9), (9);
+CREATE TABLE t2 (a int NOT NULL );
+INSERT INTO t2 VALUES (9);
+CREATE TABLE t3 (a int NOT NULL, b int);
+INSERT INTO t3 VALUES (19,9);
+CREATE TABLE t4 (b int) ;
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a;
+a	a	a	b	b
+9	9	19	9	NULL
+9	9	19	9	NULL
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a
+WHERE t3.a IS NULL;
+a	a	a	b	b
+EXPLAIN EXTENDED
+SELECT * FROM t1 LEFT JOIN
+((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+ON t1.a=t2.a
+WHERE t3.a IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
+1	SIMPLE	t2	hash_ALL	NULL	#hash#$hj	4	test.t1.a	1	100.00	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	t3	hash_ALL	NULL	#hash#$hj	5	test.t1.a	1	100.00	Using where; Not exists; Using join buffer (incremental, BNLH join)
+1	SIMPLE	t4	hash_ALL	NULL	#hash#$hj	5	test.t3.a	0	0.00	Using where; Using join buffer (incremental, BNLH join)
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`b` AS `b` from `test`.`t1` left join (`test`.`t2` left join `test`.`t3` on(((`test`.`t2`.`a` = `test`.`t1`.`a`) and (`test`.`t3`.`b` = `test`.`t1`.`a`))) left join `test`.`t4` on(((`test`.`t4`.`b` = `test`.`t3`.`a`) and (`test`.`t3`.`a` is not null)))) on((`test`.`t2`.`a` = `test`.`t1`.`a`)) where isnull(`test`.`t3`.`a`)
+DROP TABLE t1,t2,t3,t4;
 End of 5.0 tests
 CREATE TABLE t5 (a int, b int, c int, PRIMARY KEY(a), KEY b_i (b));
 CREATE TABLE t6 (a int, b int, c int, PRIMARY KEY(a), KEY b_i (b));

mysql-test/t/join_nested.test

@@ -1236,5 +1236,35 @@ SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a
 DROP TABLE t1, t2, t3;
 
 
+#
+# LP BUG#817360: Nested left joins + not-exist optimization
+#
+
+CREATE TABLE t1 (a int NOT NULL );
+INSERT INTO t1 VALUES (9), (9);
+
+CREATE TABLE t2 (a int NOT NULL );
+INSERT INTO t2 VALUES (9);
+
+CREATE TABLE t3 (a int NOT NULL, b int);
+INSERT INTO t3 VALUES (19,9);
+
+CREATE TABLE t4 (b int) ;
+
+SELECT * FROM t1 LEFT JOIN
+             ((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+             ON t1.a=t2.a;
+SELECT * FROM t1 LEFT JOIN
+             ((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+             ON t1.a=t2.a
+   WHERE t3.a IS NULL;
+EXPLAIN EXTENDED
+SELECT * FROM t1 LEFT JOIN
+             ((t2 LEFT JOIN t3 ON t2.a=t3.b) LEFT JOIN t4 ON t3.a=t4.b)
+             ON t1.a=t2.a
+   WHERE t3.a IS NULL;
+
+DROP TABLE t1,t2,t3,t4;
+
 --echo End of 5.0 tests
 

sql/sql_select.cc

@@ -15114,7 +15114,6 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       condition is true => a match is found.
     */
     bool found= 1;
-    bool use_not_exists_opt= 0;
     while (join_tab->first_unmatched && found)
     {
       /*
@@ -15130,8 +15129,6 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       first_unmatched->found= 1;
       for (JOIN_TAB *tab= first_unmatched; tab <= join_tab; tab++)
       {
-        if (tab->table->reginfo.not_exists_optimize)
-          use_not_exists_opt= 1;
         /* Check all predicates that has just been activated. */
         /*
           Actually all predicates non-guarded by first_unmatched->found
@@ -15142,7 +15139,11 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
         {
           /* The condition attached to table tab is false */
           if (tab == join_tab)
+          {
             found= 0;
+            if (tab->table->reginfo.not_exists_optimize)
+              DBUG_RETURN(NESTED_LOOP_NO_MORE_ROWS);
+          }            
           else
           {
             /*
@@ -15150,7 +15151,10 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
               not to the last table of the current nest level.
             */
             join->return_tab= tab;
-            DBUG_RETURN(NESTED_LOOP_OK);
+            if (tab->table->reginfo.not_exists_optimize)
+              DBUG_RETURN(NESTED_LOOP_NO_MORE_ROWS);
+            else
+              DBUG_RETURN(NESTED_LOOP_OK);
           }
         }
       }
@@ -15164,8 +15168,6 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       join_tab->first_unmatched= first_unmatched;
     }
 
-    if (use_not_exists_opt)
-      DBUG_RETURN(NESTED_LOOP_NO_MORE_ROWS);
     JOIN_TAB *return_tab= join->return_tab;
     join_tab->found_match= TRUE;