Bug #22781: SQL_BIG_RESULT fails to influence sort plan

 Currently SQL_BIG_RESULT is checked only at compile time.
 However, additional optimizations may take place after
 this check that change the sort method from 'filesort'
 to sorting via index. As a result the actual plan
 executed is not the one specified by the SQL_BIG_RESULT
 hint. Similarly, there is no such test when executing
 EXPLAIN, resulting in incorrect output.
 The patch corrects the problem by testing for
 SQL_BIG_RESULT both during the explain and execution
 phases.


mysql-test/r/bdb.result:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - updated sql_big_result testcase
mysql-test/r/group_by.result:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - test case with MyISAM
mysql-test/r/innodb.result:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - updated sql_big_result testcase
mysql-test/r/innodb_mysql.result:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - test case with InnoDB
mysql-test/r/myisam.result:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - updated sql_big_result testcase
mysql-test/t/group_by.test:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - test case with MyISAM
mysql-test/t/innodb_mysql.test:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - test case with InnoDB
sql/sql_select.cc:
  Bug #22781: SQL_BIG_RESULT fails to influence sort plan
   - When SQL_BIG_RESULT is specified, disable the optimization performed
  at execution/explain time that decides to use an index instead
  of filesort.

mysql-test/r/group_by.result

@@ -303,10 +303,10 @@ spid	sum(userid)
 1	1
 explain select sql_big_result score,count(*) from t1 group by score desc;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index
+1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index; Using filesort
 explain select sql_big_result score,count(*) from t1 group by score desc order by null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index
+1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index; Using filesort
 select sql_big_result score,count(*) from t1 group by score desc;
 score	count(*)
 3	5
@@ -821,3 +821,66 @@ a	b	real_b
 68	France	France
 DROP VIEW v1;
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a INT PRIMARY KEY, b INT, key (b));
+INSERT INTO t1 VALUES (1,      1);
+INSERT INTO t1 SELECT  a + 1 , MOD(a + 1 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 2 , MOD(a + 2 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 4 , MOD(a + 4 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 8 , MOD(a + 8 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 16, MOD(a + 16, 20) FROM t1;
+INSERT INTO t1 SELECT  a + 32, MOD(a + 32, 20) FROM t1;
+INSERT INTO t1 SELECT  a + 64, MOD(a + 64, 20) FROM t1;
+SELECT MIN(b), MAX(b) from t1;
+MIN(b)	MAX(b)
+0	19
+EXPLAIN SELECT b, sum(1) FROM t1 GROUP BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	b	5	NULL	128	Using index
+EXPLAIN SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	b	5	NULL	128	Using index; Using filesort
+SELECT b, sum(1) FROM t1 GROUP BY b;
+b	sum(1)
+0	6
+1	7
+2	7
+3	7
+4	7
+5	7
+6	7
+7	7
+8	7
+9	6
+10	6
+11	6
+12	6
+13	6
+14	6
+15	6
+16	6
+17	6
+18	6
+19	6
+SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
+b	sum(1)
+0	6
+1	7
+2	7
+3	7
+4	7
+5	7
+6	7
+7	7
+8	7
+9	6
+10	6
+11	6
+12	6
+13	6
+14	6
+15	6
+16	6
+17	6
+18	6
+19	6
+DROP TABLE t1;

mysql-test/r/innodb_mysql.result

@@ -337,3 +337,19 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	index	NULL	fkey	5	NULL	5	Using index
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.fkey	1	Using where
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a INT PRIMARY KEY, b INT, c FLOAT, KEY b(b)) ENGINE = INNODB;
+INSERT INTO t1 VALUES (    1 , 1              , 1);
+INSERT INTO t1 SELECT  a + 1 , MOD(a + 1 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 2 , MOD(a + 2 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 4 , MOD(a + 4 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 8 , MOD(a + 8 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 16, MOD(a + 16, 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 32, MOD(a + 32, 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 64, MOD(a + 64, 20), 1 FROM t1;
+EXPLAIN SELECT b, SUM(c) FROM t1 GROUP BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	b	5	NULL	128	
+EXPLAIN SELECT SQL_BIG_RESULT b, SUM(c) FROM t1 GROUP BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	128	Using filesort
+DROP TABLE t1;

mysql-test/t/group_by.test

@@ -655,3 +655,25 @@ where t2.b=v1.a GROUP BY t2.b;
 
 DROP VIEW v1;
 DROP TABLE t1,t2;
+
+#
+# Bug#22781: SQL_BIG_RESULT fails to influence sort plan
+#
+CREATE TABLE t1 (a INT PRIMARY KEY, b INT, key (b));
+
+INSERT INTO t1 VALUES (1,      1);
+INSERT INTO t1 SELECT  a + 1 , MOD(a + 1 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 2 , MOD(a + 2 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 4 , MOD(a + 4 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 8 , MOD(a + 8 , 20) FROM t1;
+INSERT INTO t1 SELECT  a + 16, MOD(a + 16, 20) FROM t1;
+INSERT INTO t1 SELECT  a + 32, MOD(a + 32, 20) FROM t1;
+INSERT INTO t1 SELECT  a + 64, MOD(a + 64, 20) FROM t1;
+
+SELECT MIN(b), MAX(b) from t1;
+
+EXPLAIN SELECT b, sum(1) FROM t1 GROUP BY b;
+EXPLAIN SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
+SELECT b, sum(1) FROM t1 GROUP BY b;
+SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
+DROP TABLE t1;

mysql-test/t/innodb_mysql.test

@@ -302,3 +302,21 @@ SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id
   WHERE t1.name LIKE 'A%' OR FALSE;
 
 DROP TABLE t1,t2;
+
+#
+# Bug#22781: SQL_BIG_RESULT fails to influence sort plan
+#
+CREATE TABLE t1 (a INT PRIMARY KEY, b INT, c FLOAT, KEY b(b)) ENGINE = INNODB;
+
+INSERT INTO t1 VALUES (    1 , 1              , 1);
+INSERT INTO t1 SELECT  a + 1 , MOD(a + 1 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 2 , MOD(a + 2 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 4 , MOD(a + 4 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 8 , MOD(a + 8 , 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 16, MOD(a + 16, 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 32, MOD(a + 32, 20), 1 FROM t1;
+INSERT INTO t1 SELECT  a + 64, MOD(a + 64, 20), 1 FROM t1;
+
+EXPLAIN SELECT b, SUM(c) FROM t1 GROUP BY b;
+EXPLAIN SELECT SQL_BIG_RESULT b, SUM(c) FROM t1 GROUP BY b;
+DROP TABLE t1;

sql/sql_select.cc

@@ -1400,6 +1400,7 @@ JOIN::exec()
       skip_sort_order= 0;
     }
     if (order && 
+        (order != group_list || !(select_options & SELECT_BIG_RESULT)) &&
 	(const_tables == tables ||
  	 ((simple_order || skip_sort_order) &&
 	  test_if_skip_sort_order(&join_tab[const_tables], order,
@@ -11995,11 +11996,17 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   table=  tab->table;
   select= tab->select;
 
-  if (test_if_skip_sort_order(tab,order,select_limit,0))
+  /*
+    When there is SQL_BIG_RESULT do not sort using index for GROUP BY,
+    and thus force sorting on disk.
+  */
+  if ((order != join->group_list || 
+       !(join->select_options & SELECT_BIG_RESULT)) &&
+      test_if_skip_sort_order(tab,order,select_limit,0))
     DBUG_RETURN(0);
   if (!(sortorder=make_unireg_sortorder(order,&length)))
     goto err;				/* purecov: inspected */
-  /* It's not fatal if the following alloc fails */
+
   table->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),
                                              MYF(MY_WME | MY_ZEROFILL));
   table->status=0;				// May be wrong if quick_select