Fixed bug #49322.

When not-exists optimization was applied to a table that
happened to be an inner table of two outer joins, one
embedded into another, then setting the match flag for
the embedding outer join on could be skipped. This caused
generation of extra null complemented rows.
Made sure that the match flags are set correctly in all cases
when not-exists optimization is used.  

mysql-test/r/join_nested.result

@@ -1743,4 +1743,62 @@ ON t4.carrier = t1.carrier;
 COUNT(*)
 6
 DROP TABLE t1,t2,t3,t4,t5;
+CREATE TABLE t1 (
+pk int NOT NULL AUTO_INCREMENT PRIMARY KEY,
+a int DEFAULT NULL,
+KEY idx(a)
+);
+CREATE TABLE t2 (
+pk int  NOT NULL AUTO_INCREMENT PRIMARY KEY,
+a int DEFAULT NULL,
+KEY idx(a)
+);
+CREATE TABLE t3 (
+pk int NOT NULL AUTO_INCREMENT PRIMARY KEY,
+a int DEFAULT NULL,
+KEY idx(a)
+);
+INSERT INTO t1 VALUES 
+(1,2), (2,7), (3,5), (4,7), (5,5), (6,NULL), (7,NULL), (8,9);
+INSERT INTO t2 VALUES 
+(1,NULL), (4,2), (5,2), (3,4), (2,8);
+INSERT INTO t3 VALUES
+(1,9), (2,2), (3,5), (4,2), (5,7), (6,0), (7,5);
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a;
+pk	a	pk	a	pk	a
+1	2	4	2	2	2
+1	2	4	2	4	2
+1	2	5	2	2	2
+1	2	5	2	4	2
+2	7	NULL	NULL	NULL	NULL
+3	5	NULL	NULL	NULL	NULL
+4	7	NULL	NULL	NULL	NULL
+5	5	NULL	NULL	NULL	NULL
+6	NULL	NULL	NULL	NULL	NULL
+7	NULL	NULL	NULL	NULL	NULL
+8	9	NULL	NULL	NULL	NULL
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a
+WHERE t2.pk IS NULL;
+pk	a	pk	a	pk	a
+2	7	NULL	NULL	NULL	NULL
+3	5	NULL	NULL	NULL	NULL
+4	7	NULL	NULL	NULL	NULL
+5	5	NULL	NULL	NULL	NULL
+6	NULL	NULL	NULL	NULL	NULL
+7	NULL	NULL	NULL	NULL	NULL
+8	9	NULL	NULL	NULL	NULL
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a
+WHERE t3.pk IS NULL;
+pk	a	pk	a	pk	a
+2	7	NULL	NULL	NULL	NULL
+3	5	NULL	NULL	NULL	NULL
+4	7	NULL	NULL	NULL	NULL
+5	5	NULL	NULL	NULL	NULL
+6	NULL	NULL	NULL	NULL	NULL
+7	NULL	NULL	NULL	NULL	NULL
+8	9	NULL	NULL	NULL	NULL
+DROP TABLE t1, t2, t3;
 End of 5.0 tests

mysql-test/t/join_nested.test

@@ -1196,5 +1196,45 @@ SELECT COUNT(*)
 
 DROP TABLE t1,t2,t3,t4,t5;
 
+#
+# BUG#49322: Nested left joins + not-exist optimization
+#
+
+CREATE TABLE t1 (
+  pk int NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  a int DEFAULT NULL,
+  KEY idx(a)
+);
+CREATE TABLE t2 (
+  pk int  NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  a int DEFAULT NULL,
+  KEY idx(a)
+);
+CREATE TABLE t3 (
+  pk int NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  a int DEFAULT NULL,
+  KEY idx(a)
+);
+
+INSERT INTO t1 VALUES 
+  (1,2), (2,7), (3,5), (4,7), (5,5), (6,NULL), (7,NULL), (8,9);
+INSERT INTO t2 VALUES 
+  (1,NULL), (4,2), (5,2), (3,4), (2,8);
+INSERT INTO t3 VALUES
+  (1,9), (2,2), (3,5), (4,2), (5,7), (6,0), (7,5);
+
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+  FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a;
+
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+  FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a
+  WHERE t2.pk IS NULL;
+
+SELECT t1.pk, t1.a, t2.pk, t2.a,t3.pk, t3.a 
+  FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t3.a=t2.a) ON t2.a=t1.a
+  WHERE t3.pk IS NULL;
+
+DROP TABLE t1, t2, t3;
+
 --echo End of 5.0 tests
 

sql/sql_select.cc

@@ -11738,6 +11738,7 @@ 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)
     {
       /*
@@ -11754,7 +11755,7 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       for (JOIN_TAB *tab= first_unmatched; tab <= join_tab; tab++)
       {
         if (tab->table->reginfo.not_exists_optimize)
-          return NESTED_LOOP_NO_MORE_ROWS;
+          use_not_exists_opt= 1;
         /* Check all predicates that has just been activated. */
         /*
           Actually all predicates non-guarded by first_unmatched->found
@@ -11787,6 +11788,9 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       join_tab->first_unmatched= first_unmatched;
     }
 
+    if (use_not_exists_opt)
+      return NESTED_LOOP_NO_MORE_ROWS;
+
     /*
       It was not just a return to lower loop level when one
       of the newly activated predicates is evaluated as false