Removed /2 of InnoDB ref_per_key[] estimates

The original code was there to favor index search over table scan.
This is not needed anymore as the cost calculations for table scans
and index lookups are now more exact.

mysql-test/main/derived_split_innodb.result

@@ -208,8 +208,8 @@ t2
 where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	1	
-1	PRIMARY	t1	ref	idx	idx	4	test.t2.id	1	
-1	PRIMARY	<derived2>	ref	key0	key0	9	test.t2.id,test.t1.id	1	
+1	PRIMARY	<derived2>	ref	key1	key1	4	test.t2.id	1	
+1	PRIMARY	t1	ref	idx	idx	4	test.t2.id	3	Using where
 2	DERIVED	t3	ref	idx1,idx2	idx1	4	const	5	Using where; Using index
 select t1.id, t1.itemid, dt.id, t2.id
 from t1,
@@ -227,8 +227,8 @@ t2
 where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	1	
-1	PRIMARY	t1	ref	idx	idx	4	test.t2.id	1	
-1	PRIMARY	<derived2>	ref	key0	key0	9	test.t2.id,test.t1.id	1	
+1	PRIMARY	<derived2>	ref	key1	key1	4	test.t2.id	1	
+1	PRIMARY	t1	ref	idx	idx	4	test.t2.id	3	Using where
 2	DERIVED	t3	ref	idx1	idx1	4	const	5	Using where; Using index
 select t1.id, t1.itemid, dt.id, t2.id
 from t1,

mysql-test/main/join_outer_innodb.result

@@ -448,9 +448,9 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t12	eq_ref	PRIMARY	PRIMARY	4	test.t11.k3	1	Using where
 1	SIMPLE	l2	eq_ref	PRIMARY	PRIMARY	4	test.t11.k4	1	Using where
 1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
-1	SIMPLE	t13	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where
+1	SIMPLE	t13	ref	PRIMARY,m3	m3	8	const,test.t1.a1	3	Using index
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where
-1	SIMPLE	m2	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where
+1	SIMPLE	m2	ref	PRIMARY,m3	m3	8	const,test.t1.a1	3	Using index
 1	SIMPLE	l3	eq_ref	PRIMARY	PRIMARY	4	test.m2.m2	1	Using where
 1	SIMPLE	t14	eq_ref	PRIMARY	PRIMARY	2	test.t1.a8	1	Using where
 1	SIMPLE	t15	eq_ref	PRIMARY	PRIMARY	2	test.t1.a9	1	Using where
@@ -471,9 +471,9 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t12	eq_ref	PRIMARY	PRIMARY	4	test.t11.k3	1	Using where
 1	SIMPLE	l2	eq_ref	PRIMARY	PRIMARY	4	test.t11.k4	1	Using where
 1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
-1	SIMPLE	t13	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where
+1	SIMPLE	t13	ref	PRIMARY,m3	m3	8	const,test.t1.a1	3	Using index
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where
-1	SIMPLE	m2	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where
+1	SIMPLE	m2	ref	PRIMARY,m3	m3	8	const,test.t1.a1	3	Using index
 1	SIMPLE	l3	eq_ref	PRIMARY	PRIMARY	4	test.m2.m2	1	Using where
 1	SIMPLE	t14	eq_ref	PRIMARY	PRIMARY	2	test.t1.a8	1	Using where
 1	SIMPLE	t15	eq_ref	PRIMARY	PRIMARY	2	test.t1.a9	1	Using where

mysql-test/main/mdev-25830.result

@@ -25,8 +25,8 @@ ORDER  BY sysapproval_approver0.`order`
 LIMIT  0, 50 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
 1	SIMPLE	task2	range	PRIMARY,sys_class_name_2,sys_domain_path	PRIMARY	96	NULL	1	0.00	100.00	100.00	Using where; Using temporary; Using filesort
-1	SIMPLE	task1	ref	PRIMARY,task_parent,sys_class_name_2,sys_domain_path	task_parent	99	test.task2.sys_id	1	NULL	100.00	NULL	Using index condition; Using where
-1	SIMPLE	sysapproval_approver0	ref	sysapproval_approver_ref5,sys_domain_path,sysapproval_approver_CHG1975376	sysapproval_approver_ref5	99	test.task1.sys_id	1	NULL	100.00	NULL	Using index condition; Using where
+1	SIMPLE	task1	ref	PRIMARY,task_parent,sys_class_name_2,sys_domain_path	task_parent	99	test.task2.sys_id	2	NULL	100.00	NULL	Using index condition; Using where
+1	SIMPLE	sysapproval_approver0	ref	sysapproval_approver_ref5,sys_domain_path,sysapproval_approver_CHG1975376	sysapproval_approver_ref5	99	test.task1.sys_id	3	NULL	100.00	NULL	Using index condition; Using where
 set optimizer_use_condition_selectivity=4;
 analyze SELECT sysapproval_approver0.`sys_id`
 FROM   ((sysapproval_approver sysapproval_approver0
@@ -48,8 +48,8 @@ ORDER  BY sysapproval_approver0.`order`
 LIMIT  0, 50 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
 1	SIMPLE	task2	range	PRIMARY,sys_class_name_2,sys_domain_path	PRIMARY	96	NULL	1	0.00	100.00	100.00	Using where; Using temporary; Using filesort
-1	SIMPLE	task1	ref	PRIMARY,task_parent,sys_class_name_2,sys_domain_path	task_parent	99	test.task2.sys_id	1	NULL	100.00	NULL	Using index condition; Using where
-1	SIMPLE	sysapproval_approver0	ref	sysapproval_approver_ref5,sys_domain_path,sysapproval_approver_CHG1975376	sysapproval_approver_ref5	99	test.task1.sys_id	1	NULL	100.00	NULL	Using index condition; Using where
+1	SIMPLE	task1	ref	PRIMARY,task_parent,sys_class_name_2,sys_domain_path	task_parent	99	test.task2.sys_id	2	NULL	100.00	NULL	Using index condition; Using where
+1	SIMPLE	sysapproval_approver0	ref	sysapproval_approver_ref5,sys_domain_path,sysapproval_approver_CHG1975376	sysapproval_approver_ref5	99	test.task1.sys_id	3	NULL	100.00	NULL	Using index condition; Using where
 drop table sysapproval_approver,task;
 set global innodb_stats_persistent= @innodb_stats_persistent_save;
 set global innodb_stats_persistent_sample_pages=

mysql-test/main/order_by_innodb.result

@@ -258,7 +258,7 @@ dd.d1, dd.d2, dd.id limit 1
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	#	
 1	PRIMARY	t2	eq_ref	PRIMARY,id2	id2	8	test.t1.id,func	#	Using where; Using index
-2	DEPENDENT SUBQUERY	dd	ref	id2,for_latest_sort	id2	4	test.t1.id	#	Using where; Using filesort
+2	DEPENDENT SUBQUERY	dd	range	id2,for_latest_sort	for_latest_sort	6	NULL	#	Using where
 drop table t1,t2,t3;
 # End of 10.2 tests
 #

mysql-test/main/subselect2.result

@@ -125,8 +125,8 @@ DOCID	DOCNAME	DOCTYPEID	FOLDERID	AUTHOR	CREATED	TITLE	SUBTITLE	DOCABSTRACT	PUBLI
 c373e9f5ad07993f3859444553544200	Last Discussion	c373e9f5ad079174ff17444553544200	c373e9f5ad0796c0eca4444553544200	Goldilocks	2003-06-09 11:21:06	Title: Last Discussion	NULL	Setting new abstract and keeping doc checked out	2003-06-09 10:51:26	2003-06-09 10:51:26	NULL	NULL	NULL	03eea05112b845949f3fd03278b5fe43	2003-06-09 11:21:06	admin	0	NULL	Discussion	NULL	NULL
 EXPLAIN SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3_a.FOLDERID FROM t3 as t3_a WHERE t3_a.PARENTID IN(SELECT t3_b.FOLDERID FROM t3 as t3_b WHERE t3_b.PARENTID IN(SELECT t3_c.FOLDERID FROM t3 as t3_c WHERE t3_c.PARENTID IN(SELECT t3_d.FOLDERID FROM t3 as t3_d WHERE t3_d.PARENTID IN(SELECT t3_e.FOLDERID FROM t3 as t3_e WHERE t3_e.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3_e.FOLDERNAME = 'Level1') AND t3_d.FOLDERNAME = 'Level2') AND t3_c.FOLDERNAME = 'Level3') AND t3_b.FOLDERNAME = 'CopiedFolder') AND t3_a.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t2	ALL	DDOCTYPEID_IDX,DFOLDERID_IDX	NULL	NULL	NULL	9	Using where
-1	PRIMARY	t4	eq_ref	PRIMARY	PRIMARY	34	test.t2.DOCTYPEID	1	
+1	PRIMARY	t4	ALL	PRIMARY	NULL	NULL	NULL	10	
+1	PRIMARY	t2	ALL	DDOCTYPEID_IDX,DFOLDERID_IDX	NULL	NULL	NULL	9	Using where; Using join buffer (flat, BNL join)
 1	PRIMARY	t1	eq_ref	PRIMARY	PRIMARY	34	test.t2.DOCID	1	
 1	PRIMARY	t3_a	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t2.FOLDERID	1	Using where
 1	PRIMARY	t3_b	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3_a.PARENTID	1	Using where

mysql-test/main/subselect_innodb.result

@@ -560,6 +560,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 #
 # MDEV-6081: ORDER BY+ref(const): selectivity is very incorrect (MySQL Bug#14338686)
 #
+insert into t2 select seq,seq,seq from seq_10000_to_11000;
 alter table t2 add key2 int;
 update t2 set key2=key1;
 alter table t2 add key(key2);
@@ -580,6 +581,29 @@ t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	#	
 2	DEPENDENT SUBQUERY	t2	ref	key1	key1	5	test.t1.a	#	Using where; Using filesort
+select 
+(SELECT 
+concat(id, '-', key1, '-', col1)
+FROM t2
+WHERE t2.key1 = t1.a
+ORDER BY t2.key2 ASC LIMIT 1)
+from 
+t1;
+(SELECT 
+concat(id, '-', key1, '-', col1)
+FROM t2
+WHERE t2.key1 = t1.a
+ORDER BY t2.key2 ASC LIMIT 1)
+100-0-123456
+101-1-123456
+102-2-123456
+103-3-123456
+104-4-123456
+105-5-123456
+106-6-123456
+107-7-123456
+108-8-123456
+109-9-123456
 drop table t1,t2;
 #
 # MDEV-12931: semi-join in ON expression of STRAIGHT_JOIN 

mysql-test/main/subselect_innodb.test

 -- source include/no_valgrind_without_big.inc
 -- source include/have_innodb.inc
+-- source include/have_sequence.inc
 
 # Note: the tests uses only non-semijoin subqueries so semi-join switch
 #       settings are not relevant.
@@ -568,6 +569,11 @@ from
 --echo # MDEV-6081: ORDER BY+ref(const): selectivity is very incorrect (MySQL Bug#14338686)
 --echo #
 
+
+# Table t2 has 100 equal values / key value, which causes it to prefer index scan instead of ref
+# Fix it by adding more different values to key1
+insert into t2 select seq,seq,seq from seq_10000_to_11000;
+
 alter table t2 add key2 int;
 update t2 set key2=key1;
 alter table t2 add key(key2);
@@ -583,6 +589,14 @@ explain select
     ORDER BY t2.key2 ASC LIMIT 1)
 from 
   t1;
+select 
+   (SELECT 
+      concat(id, '-', key1, '-', col1)
+    FROM t2
+    WHERE t2.key1 = t1.a
+    ORDER BY t2.key2 ASC LIMIT 1)
+from 
+  t1;
 
 drop table t1,t2;
 

mysql-test/main/update_use_source.result

@@ -317,7 +317,7 @@ rollback;
 explain update t1 set c1=0 where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 > 3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	range	t1_c2	t1_c2	5	NULL	2	Using where
-2	DEPENDENT SUBQUERY	a	ref	t1_c2	t1_c2	5	test.t1.c2	4	Using index
+2	DEPENDENT SUBQUERY	a	ref	t1_c2	t1_c2	5	test.t1.c2	8	Using index
 start transaction;
 update t1 set c1=c1+10 where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 >= 3;
 affected rows: 4

mysql-test/suite/innodb/r/innodb-index-online.result

@@ -204,7 +204,7 @@ CREATE INDEX c2d ON t1(c2);
 SHOW INDEX FROM t1;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
 t1	0	PRIMARY	1	c1	A	80	NULL	NULL		BTREE			NO
-t1	1	c2d	1	c2	A	10	NULL	NULL	YES	BTREE			NO
+t1	1	c2d	1	c2	A	5	NULL	NULL	YES	BTREE			NO
 EXPLAIN SELECT COUNT(*) FROM t1 WHERE c2 > 3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c2d	c2d	5	NULL	32	Using where; Using index

mysql-test/suite/innodb/r/innodb_bug57252.result

 cardinality
-2
+1
 Table	Op	Msg_type	Msg_text
 test.bug57252	analyze	status	Engine-independent statistics collected
 test.bug57252	analyze	status	OK

mysql-test/suite/innodb/r/innodb_stats.result

@@ -151,7 +151,7 @@ INDEX_NAME	a_key
 SEQ_IN_INDEX	1
 COLUMN_NAME	a
 COLLATION	A
-CARDINALITY	2
+CARDINALITY	1
 SUB_PART	NULL
 PACKED	NULL
 NULLABLE	YES
@@ -204,7 +204,7 @@ INDEX_NAME	a_key
 SEQ_IN_INDEX	1
 COLUMN_NAME	a
 COLLATION	A
-CARDINALITY	3
+CARDINALITY	1
 SUB_PART	NULL
 PACKED	NULL
 NULLABLE	YES
@@ -257,7 +257,7 @@ INDEX_NAME	a_key
 SEQ_IN_INDEX	1
 COLUMN_NAME	a
 COLLATION	A
-CARDINALITY	2
+CARDINALITY	1
 SUB_PART	NULL
 PACKED	NULL
 NULLABLE	YES
@@ -522,7 +522,7 @@ INDEX_NAME	a_key
 SEQ_IN_INDEX	1
 COLUMN_NAME	a
 COLLATION	A
-CARDINALITY	10
+CARDINALITY	5
 SUB_PART	NULL
 PACKED	NULL
 NULLABLE	YES

mysql-test/suite/innodb/r/innodb_stats_fetch.result

@@ -131,16 +131,16 @@ FROM information_schema.statistics WHERE table_name = 'test_ps_fetch'
 ORDER BY index_name, seq_in_index;
 seq_in_index	1
 column_name	c
-cardinality	6
+cardinality	3
 seq_in_index	2
 column_name	d
-cardinality	22
+cardinality	11
 seq_in_index	1
 column_name	a
-cardinality	40
+cardinality	20
 seq_in_index	2
 column_name	b
-cardinality	200
+cardinality	90
 SELECT
 table_rows, avg_row_length, max_data_length, index_length
 FROM information_schema.tables WHERE table_name = 'test_ps_fetch';

storage/innobase/handler/ha_innodb.cc

@@ -14891,13 +14891,6 @@ ha_innobase::info_low(
 					innodb_rec_per_key(index, j,
 							   stats.records));
 
-				/* Since MySQL seems to favor table scans
-				too much over index searches, we pretend
-				index selectivity is 2 times better than
-				our estimate: */
-
-				rec_per_key_int = rec_per_key_int / 2;
-
 				if (rec_per_key_int == 0) {
 					rec_per_key_int = 1;
 				}