MDEV-6838 Using too big key for internal temp tables

update test results after the fix

mysql-test/r/derived_view.result

@@ -770,7 +770,7 @@ SELECT * FROM t1, t2, v1 WHERE t2.a=t1.a AND t2.a=v1.a AND t2.a=v1.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
 1	PRIMARY	t2	ref	a	a	4	const	1	Using index
-1	PRIMARY	<derived2>	ref	key0	key0	10	const,const	1	
+1	PRIMARY	<derived2>	ref	key0	key0	8	const,const	1	
 2	DERIVED	t3	ALL	NULL	NULL	NULL	NULL	12	Using temporary; Using filesort
 SELECT * FROM t1, t2, v1 WHERE t2.a=t1.a AND t2.a=v1.a AND t2.a=v1.b;
 a	a	a	b
@@ -1518,7 +1518,7 @@ WHERE t3.b IN (SELECT v1.b FROM  v1, t2
 WHERE t2.c = v1.c AND t2.c = v1.b AND v1.b = t3.c);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	1	
-1	PRIMARY	<derived3>	ref	key1	key1	10	const,const	0	Start temporary
+1	PRIMARY	<derived3>	ref	key1	key1	8	const,const	0	Start temporary
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using where; End temporary; Using join buffer (flat, BNL join)
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	
 SELECT * FROM t3 
@@ -1596,7 +1596,7 @@ EXPLAIN
 SELECT v1.a FROM v1,v2 WHERE v2.b = v1.b ORDER BY 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	Using where; Using filesort
-1	PRIMARY	<derived3>	ref	key0	key0	5	v1.b	2	
+1	PRIMARY	<derived3>	ref	key0	key0	4	v1.b	2	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	Using temporary; Using filesort
 DROP VIEW v1,v2;

mysql-test/r/select_jcl6.result

@@ -4417,7 +4417,7 @@ INSERT INTO t1 VALUES
 EXPLAIN SELECT 1 FROM t1 NATURAL LEFT JOIN t1 AS t2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	
-1	SIMPLE	t2	hash_ALL	a	#hash#$hj	14	test.t1.a	2	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	t2	hash_ALL	a	#hash#$hj	2	test.t1.a	2	Using where; Using join buffer (flat, BNLH join)
 SELECT 1 FROM t1 NATURAL LEFT JOIN t1 AS t2;
 1
 1
@@ -4427,7 +4427,7 @@ SELECT 1 FROM t1 NATURAL LEFT JOIN t1 AS t2;
 EXPLAIN SELECT 1 FROM t1 NATURAL LEFT JOIN t1 AS t2 FORCE INDEX(a);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	
-1	SIMPLE	t2	hash_ALL	a	#hash#$hj	14	test.t1.a	2	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	t2	hash_ALL	a	#hash#$hj	2	test.t1.a	2	Using where; Using join buffer (flat, BNLH join)
 SELECT 1 FROM t1 NATURAL LEFT JOIN t1 AS t2 FORCE INDEX(a);
 1
 1

mysql-test/r/subselect_extra.result

@@ -447,7 +447,7 @@ WHERE t3.b IN (SELECT v1.b FROM  v1, t2
 WHERE t2.c = v1.c AND t2.c = v1.b AND v1.b = t3.c);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	1	
-1	PRIMARY	<derived3>	ref	key1	key1	10	const,const	0	Start temporary
+1	PRIMARY	<derived3>	ref	key1	key1	8	const,const	0	Start temporary
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using where; End temporary; Using join buffer (flat, BNL join)
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	
 SELECT * FROM t3 

mysql-test/r/subselect_extra_no_semijoin.result

@@ -450,7 +450,7 @@ WHERE t2.c = v1.c AND t2.c = v1.b AND v1.b = t3.c);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using where
 2	DEPENDENT SUBQUERY	t2	system	NULL	NULL	NULL	NULL	1	
-2	DEPENDENT SUBQUERY	<derived3>	ref	key1	key1	10	const,const	0	Using where
+2	DEPENDENT SUBQUERY	<derived3>	ref	key1	key1	8	const,const	0	Using where
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	
 SELECT * FROM t3 
 WHERE t3.b IN (SELECT v1.b FROM  v1, t2 

mysql-test/r/subselect_sj2_jcl6.result

@@ -891,7 +891,7 @@ WHERE t3.b IN (SELECT b FROM t4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	1	
 1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
-1	PRIMARY	t2	hash_ALL	NULL	#hash#$hj	5	test.t3.a	1	Using where; Using join buffer (flat, BNLH join)
+1	PRIMARY	t2	hash_ALL	NULL	#hash#$hj	4	test.t3.a	1	Using where; Using join buffer (flat, BNLH join)
 1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	2	Using join buffer (incremental, BNL join)
 2	MATERIALIZED	t4	ALL	NULL	NULL	NULL	NULL	2	
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	1	
@@ -1161,7 +1161,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ref	PRIMARY	PRIMARY	5	const	1	Using where; Using index
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	1	Start temporary; Using join buffer (flat, BNL join)
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (incremental, BNL join)
-1	PRIMARY	t4	hash_index	NULL	#hash#$hj:PRIMARY	55:59	test.t3.t3_c	2	Using where; End temporary; Using join buffer (incremental, BNLH join)
+1	PRIMARY	t4	hash_index	NULL	#hash#$hj:PRIMARY	54:59	test.t3.t3_c	2	Using where; End temporary; Using join buffer (incremental, BNLH join)
 DROP TABLE t1,t2,t3,t4;
 #
 # MDEV-6263: Wrong result when using IN subquery with order by