Fixed bug #28188: performance degradation for outer join queries to which

'not exists' optimization is applied.

In fact 'not exists' optimization did not work anymore after the patch
introducing the evaluate_join_record function had been applied.

Corrected the evaluate_join_record function to respect the 'not_exists'
optimization.


mysql-test/r/join_outer.result:
  Added a test case for bug #28188.
mysql-test/t/join_outer.test:
  Added a test case for bug #28188.
sql/sql_select.cc:
  Fixed bug #28188: performance degradation for outer join queries to which
  'not exists' optimization is applied.
  
  Corrected the evaluate_join_record function to respect the 'not_exists'
  optimization.

mysql-test/r/join_outer.result

@@ -1214,3 +1214,28 @@ SELECT * FROM t1 LEFT JOIN t2 USING(f1) WHERE f1='Bla';
 f1	f2	f3
 bla	blah	sheep
 DROP TABLE t1,t2;
+CREATE TABLE t1 (id int PRIMARY KEY, a varchar(8));
+CREATE TABLE t2 (id int NOT NULL, b int NOT NULL, INDEX idx(id));
+INSERT INTO t1 VALUES
+(1,'aaaaaaa'), (5,'eeeeeee'), (4,'ddddddd'), (2,'bbbbbbb'), (3,'ccccccc');
+INSERT INTO t2 VALUES
+(3,10), (2,20), (5,30), (3,20), (5,10), (3,40), (3,30), (2,10), (2,40);
+EXPLAIN
+SELECT t1.id, a FROM t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t2.b IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	
+1	SIMPLE	t2	ref	idx	idx	4	test.t1.id	2	Using where; Not exists
+flush status;
+SELECT t1.id, a FROM t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t2.b IS NULL;
+id	a
+1	aaaaaaa
+4	ddddddd
+show status like 'Handler_read%';
+Variable_name	Value
+Handler_read_first	0
+Handler_read_key	5
+Handler_read_next	0
+Handler_read_prev	0
+Handler_read_rnd	0
+Handler_read_rnd_next	6
+DROP TABLE t1,t2;

mysql-test/t/join_outer.test

@@ -825,3 +825,23 @@ SELECT * FROM t1 LEFT JOIN t2 USING(f1) WHERE f1='bla';
 SELECT * FROM t1 LEFT JOIN t2 USING(f1) WHERE f1='Bla';
 
 DROP TABLE t1,t2;
+
+#
+# Bug 28188: 'not exists' optimization for outer joins 
+#
+ 
+CREATE TABLE t1 (id int PRIMARY KEY, a varchar(8));
+CREATE TABLE t2 (id int NOT NULL, b int NOT NULL, INDEX idx(id));
+INSERT INTO t1 VALUES
+  (1,'aaaaaaa'), (5,'eeeeeee'), (4,'ddddddd'), (2,'bbbbbbb'), (3,'ccccccc');
+INSERT INTO t2 VALUES
+  (3,10), (2,20), (5,30), (3,20), (5,10), (3,40), (3,30), (2,10), (2,40);
+
+EXPLAIN
+SELECT t1.id, a FROM t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t2.b IS NULL;
+
+flush status;
+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;

sql/sql_select.cc

@@ -10526,7 +10526,6 @@ static enum_nested_loop_state
 evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
                      int error, my_bool *report_error)
 {
-  bool not_exists_optimize= join_tab->table->reginfo.not_exists_optimize;
   bool not_used_in_distinct=join_tab->not_used_in_distinct;
   ha_rows found_records=join->found_records;
   COND *select_cond= join_tab->select_cond;
@@ -10563,6 +10562,8 @@ 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)
+          return NESTED_LOOP_NO_MORE_ROWS;
         /* Check all predicates that has just been activated. */
         /*
           Actually all predicates non-guarded by first_unmatched->found
@@ -10608,8 +10609,6 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
     if (found)
     {
       enum enum_nested_loop_state rc;
-      if (not_exists_optimize)
-        return NESTED_LOOP_NO_MORE_ROWS;
       /* A match from join_tab is found for the current partial join. */
       rc= (*join_tab->next_select)(join, join_tab+1, 0);
       if (rc != NESTED_LOOP_OK && rc != NESTED_LOOP_NO_MORE_ROWS)