Fixed LP bug #702310 / bug #59493.

An assertion failure was triggered for a 6-way join query that uses two
join buffers.
The failure happened because every call of the function flush_cached_records()
saved and restored status of all tables before the table join_tab. It
must do it only for those of them that follow the last table that uses
a join buffer.

mysql-test/r/select.result

@@ -4796,4 +4796,83 @@ SELECT 1 FROM t1 ORDER BY a COLLATE latin1_german2_ci;
 1
 1
 DROP TABLE t1;
+#
+# Bug #702310: usage of 2 join buffers after ref access to an empty table 
+#
+CREATE TABLE t1 (f1 int) ;
+INSERT INTO t1 VALUES (9);
+CREATE TABLE t2 (f1 int);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+CREATE TABLE t3 (f1 int);
+INSERT INTO t3 VALUES (17);
+CREATE TABLE t4  (f1 int PRIMARY KEY, f2 varchar(1024)) ;
+CREATE TABLE t5 (f1 int) ;
+INSERT INTO t5 VALUES (20),(5);
+CREATE TABLE t6(f1 int);
+INSERT INTO t6 VALUES (9),(7);
+SET SESSION join_buffer_size = 9000;
+EXPLAIN
+SELECT STRAIGHT_JOIN * FROM t2, (t1 LEFT JOIN (t3,t4) ON t1.f1 = t4.f1), t5, t6;
+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	12	
+1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	1	
+1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	4	const	1	
+1	SIMPLE	t5	ALL	NULL	NULL	NULL	NULL	2	Using join buffer
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	2	Using join buffer
+SELECT STRAIGHT_JOIN * FROM t2, (t1 LEFT JOIN (t3,t4) ON t1.f1 = t4.f1), t5, t6;
+f1	f1	f1	f1	f2	f1	f1
+3	9	NULL	NULL	NULL	20	9
+7	9	NULL	NULL	NULL	20	9
+18	9	NULL	NULL	NULL	20	9
+3	9	NULL	NULL	NULL	20	9
+7	9	NULL	NULL	NULL	20	9
+18	9	NULL	NULL	NULL	20	9
+3	9	NULL	NULL	NULL	20	9
+3	9	NULL	NULL	NULL	20	7
+7	9	NULL	NULL	NULL	20	7
+18	9	NULL	NULL	NULL	20	7
+3	9	NULL	NULL	NULL	20	7
+7	9	NULL	NULL	NULL	20	7
+18	9	NULL	NULL	NULL	20	7
+3	9	NULL	NULL	NULL	20	7
+3	9	NULL	NULL	NULL	5	9
+7	9	NULL	NULL	NULL	5	9
+18	9	NULL	NULL	NULL	5	9
+3	9	NULL	NULL	NULL	5	9
+7	9	NULL	NULL	NULL	5	9
+18	9	NULL	NULL	NULL	5	9
+3	9	NULL	NULL	NULL	5	9
+3	9	NULL	NULL	NULL	5	7
+7	9	NULL	NULL	NULL	5	7
+18	9	NULL	NULL	NULL	5	7
+3	9	NULL	NULL	NULL	5	7
+7	9	NULL	NULL	NULL	5	7
+18	9	NULL	NULL	NULL	5	7
+3	9	NULL	NULL	NULL	5	7
+7	9	NULL	NULL	NULL	20	9
+18	9	NULL	NULL	NULL	20	9
+3	9	NULL	NULL	NULL	20	9
+7	9	NULL	NULL	NULL	20	9
+18	9	NULL	NULL	NULL	20	9
+7	9	NULL	NULL	NULL	5	9
+18	9	NULL	NULL	NULL	5	9
+7	9	NULL	NULL	NULL	20	7
+18	9	NULL	NULL	NULL	20	7
+3	9	NULL	NULL	NULL	20	7
+7	9	NULL	NULL	NULL	20	7
+18	9	NULL	NULL	NULL	20	7
+7	9	NULL	NULL	NULL	5	7
+18	9	NULL	NULL	NULL	5	7
+3	9	NULL	NULL	NULL	5	9
+7	9	NULL	NULL	NULL	5	9
+18	9	NULL	NULL	NULL	5	9
+3	9	NULL	NULL	NULL	5	7
+7	9	NULL	NULL	NULL	5	7
+18	9	NULL	NULL	NULL	5	7
+SET SESSION join_buffer_size = DEFAULT;
+DROP TABLE t1,t2,t3,t4,t5,t6;
 End of 5.1 tests

mysql-test/t/select.test

@@ -4087,5 +4087,38 @@ EXPLAIN SELECT 1 FROM t1 ORDER BY a COLLATE latin1_german2_ci;
 SELECT 1 FROM t1 ORDER BY a COLLATE latin1_german2_ci;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #702310: usage of 2 join buffers after ref access to an empty table 
+--echo #
+
+CREATE TABLE t1 (f1 int) ;
+INSERT INTO t1 VALUES (9);
+
+CREATE TABLE t2 (f1 int);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+INSERT INTO t2 VALUES (3),(7),(18);
+
+CREATE TABLE t3 (f1 int);
+INSERT INTO t3 VALUES (17);
+
+CREATE TABLE t4  (f1 int PRIMARY KEY, f2 varchar(1024)) ;
+
+CREATE TABLE t5 (f1 int) ;
+INSERT INTO t5 VALUES (20),(5);
+
+CREATE TABLE t6(f1 int);
+INSERT INTO t6 VALUES (9),(7);
+
+SET SESSION join_buffer_size = 9000;
+
+EXPLAIN
+SELECT STRAIGHT_JOIN * FROM t2, (t1 LEFT JOIN (t3,t4) ON t1.f1 = t4.f1), t5, t6;
+SELECT STRAIGHT_JOIN * FROM t2, (t1 LEFT JOIN (t3,t4) ON t1.f1 = t4.f1), t5, t6;
+
+SET SESSION join_buffer_size = DEFAULT;
+
+DROP TABLE t1,t2,t3,t4,t5,t6;
 
 --echo End of 5.1 tests

sql/sql_select.cc

@@ -11957,7 +11957,8 @@ flush_cached_records(JOIN *join,JOIN_TAB *join_tab,bool skip_last)
     return error < 0 ? NESTED_LOOP_NO_MORE_ROWS: NESTED_LOOP_ERROR;
   }
 
-  for (JOIN_TAB *tmp=join->join_tab; tmp != join_tab ; tmp++)
+  for (JOIN_TAB *tmp= join_tab-1;
+       tmp >= join->join_tab && !tmp->cache.buff; tmp--)
   {
     tmp->status=tmp->table->status;
     tmp->table->status=0;
@@ -12015,7 +12016,8 @@ flush_cached_records(JOIN *join,JOIN_TAB *join_tab,bool skip_last)
   reset_cache_write(&join_tab->cache);
   if (error > 0)				// Fatal error
     return NESTED_LOOP_ERROR;                   /* purecov: inspected */
-  for (JOIN_TAB *tmp2=join->join_tab; tmp2 != join_tab ; tmp2++)
+  for (JOIN_TAB *tmp2= join_tab-1;
+       tmp2 >= join->join_tab && !tmp2->cache.buff; tmp2--)
     tmp2->table->status=tmp2->status;
   return NESTED_LOOP_OK;
 }