Adjust cost for re-creating a row from the JOIN CACHE

Creating a record from the join cache is faster than getting a row from
the engine (less and simpler code to execute).

Added JOIN_CACHE_ROW_COPY_COST_FACTOR (0.5 for now) as the factor to
take this into account. This is multiplied with ROW_COPY_COST.

Other things:
- Added cost of copying rows to hash join, similar to join_cache joins.

mysql-test/main/select_safe.result

@@ -67,6 +67,7 @@ test.t1	analyze	status	OK
 insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
 insert into t1 values (null,"b"),(null,"b"),(null,"c"),(null,"c"),(null,"d"),(null,"d"),(null,"e"),(null,"e"),(null,"a"),(null,"e");
 insert into t1 values (null,"x"),(null,"x"),(null,"y"),(null,"y"),(null,"z"),(null,"z"),(null,"v"),(null,"v"),(null,"a"),(null,"v");
+set @@optimizer_where_cost=0.3;
 explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	b	NULL	NULL	NULL	11	

mysql-test/main/select_safe.test

@@ -60,6 +60,7 @@ analyze table t1;
 insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
 insert into t1 values (null,"b"),(null,"b"),(null,"c"),(null,"c"),(null,"d"),(null,"d"),(null,"e"),(null,"e"),(null,"a"),(null,"e");
 insert into t1 values (null,"x"),(null,"x"),(null,"y"),(null,"y"),(null,"z"),(null,"z"),(null,"v"),(null,"v"),(null,"a"),(null,"v");
+set @@optimizer_where_cost=0.3;
 explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
 set MAX_SEEKS_FOR_KEY=1;
 explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;

mysql-test/main/status.result

@@ -173,7 +173,7 @@ a	a
 1	1
 SHOW SESSION STATUS LIKE 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	4.003418
+Last_query_cost	3.953418
 DROP TABLE t1;
 connect  con1,localhost,root,,;
 show status like 'com_show_status';

mysql-test/main/subselect.result

@@ -7045,8 +7045,8 @@ SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	a	a	5	NULL	2	Using where; Using index
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	4	test.t2.c	1	
+2	SUBQUERY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	1	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;

mysql-test/main/subselect4.result

@@ -1277,10 +1277,9 @@ EXPLAIN
 SELECT * FROM (t2 LEFT JOIN t1 ON t1.c1) LEFT JOIN t3 on t3.c1 WHERE 's' IN (SELECT c1 FROM t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	0	Const row not found
-1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	Using where; Start temporary; End temporary
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	Using join buffer (flat, BNL join)
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
-2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	3	Using where
 SELECT * FROM (t2 LEFT JOIN t1 ON t1.c1) LEFT JOIN t3 on t3.c1 WHERE 's' IN (SELECT c1 FROM t2);
 c1	c1	c1
 EXPLAIN

mysql-test/main/subselect_no_exists_to_in.result

@@ -7046,8 +7046,8 @@ SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	a	a	5	NULL	2	Using where; Using index
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	4	test.t2.c	1	
+2	SUBQUERY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	1	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;

mysql-test/main/subselect_no_opts.result

@@ -7039,8 +7039,8 @@ SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	a	a	5	NULL	2	Using where; Using index
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	4	test.t2.c	1	
+2	SUBQUERY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	1	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;

mysql-test/main/subselect_no_scache.result

@@ -7051,8 +7051,8 @@ SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	a	a	5	NULL	2	Using where; Using index
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	4	test.t2.c	1	
+2	SUBQUERY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	1	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;

mysql-test/main/subselect_no_semijoin.result

@@ -928,8 +928,8 @@ a	t1.a in (select t2.a from t2,t3 where t3.a=t2.a)
 explain extended SELECT t1.a, t1.a in (select t2.a from t2,t3 where t3.a=t2.a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	100.00	Using index
-2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	MATERIALIZED	t2	ref	a	a	5	test.t3.a	2	100.00	Using index
+2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	
+2	MATERIALIZED	t2	index	a	a	5	NULL	3	75.00	Using where; Using index; Using join buffer (flat, BNL join)
 Warnings:
 Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,<expr_cache><`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`a`,`test`.`t1`.`a` in ( <materialize> (/* select#2 */ select `test`.`t2`.`a` from `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t3`.`a` ), <primary_index_lookup>(`test`.`t1`.`a` in <temporary table> on distinct_key where `test`.`t1`.`a` = `<subquery2>`.`a`)))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from `test`.`t1`
 drop table t1,t2,t3;
@@ -7039,8 +7039,8 @@ SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	a	a	5	NULL	2	Using where; Using index
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	4	test.t2.c	1	
+2	SUBQUERY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	1	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1
 WHERE a = (SELECT MAX(b) FROM t2 WHERE c IN (SELECT MAX(d) FROM t3)) OR a = 10;

mysql-test/main/subselect_sj.result

@@ -205,10 +205,10 @@ a	b	a	b
 insert into t1 select (A.a + 10 * B.a),1 from t0 A, t0 B;
 explain extended select * from t1 where a in (select pk from t10 where pk<3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	103	100.00	Using where
-1	PRIMARY	t10	eq_ref	PRIMARY	PRIMARY	4	test.t1.a	1	100.00	Using index
+1	PRIMARY	t10	range	PRIMARY	PRIMARY	4	NULL	3	100.00	Using where; Using index
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	103	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t10` join `test`.`t1` where `test`.`t10`.`pk` = `test`.`t1`.`a` and `test`.`t1`.`a` < 3
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t10` join `test`.`t1` where `test`.`t1`.`a` = `test`.`t10`.`pk` and `test`.`t10`.`pk` < 3
 drop table t0, t1, t2;
 drop table t10, t11, t12;
 
@@ -2091,9 +2091,9 @@ explain
 SELECT * FROM t1 NATURAL LEFT JOIN (t2, t3) WHERE IFNULL(t2.f3,'foo') IN (SELECT * FROM t4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	
-1	PRIMARY	t4	ALL	NULL	NULL	NULL	NULL	2	Start temporary
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	5	Using where; End temporary
+1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	5	Using where
+1	PRIMARY	t4	ALL	NULL	NULL	NULL	NULL	2	Using where; Start temporary; End temporary
 SELECT * FROM t1 NATURAL LEFT JOIN (t2, t3 ) WHERE IFNULL(t2.f3,'foo') IN (SELECT * FROM t4);
 f1	f2	f3	f3
 2	0	0	0

mysql-test/main/subselect_sj_jcl6.result

@@ -216,10 +216,10 @@ a	b	a	b
 insert into t1 select (A.a + 10 * B.a),1 from t0 A, t0 B;
 explain extended select * from t1 where a in (select pk from t10 where pk<3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	103	100.00	Using where
-1	PRIMARY	t10	eq_ref	PRIMARY	PRIMARY	4	test.t1.a	1	100.00	Using index
+1	PRIMARY	t10	range	PRIMARY	PRIMARY	4	NULL	3	100.00	Using where; Using index
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	103	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t10` join `test`.`t1` where `test`.`t10`.`pk` = `test`.`t1`.`a` and `test`.`t1`.`a` < 3
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t10` join `test`.`t1` where `test`.`t1`.`a` = `test`.`t10`.`pk` and `test`.`t10`.`pk` < 3
 drop table t0, t1, t2;
 drop table t10, t11, t12;
 
@@ -2102,9 +2102,9 @@ explain
 SELECT * FROM t1 NATURAL LEFT JOIN (t2, t3) WHERE IFNULL(t2.f3,'foo') IN (SELECT * FROM t4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	
-1	PRIMARY	t4	ALL	NULL	NULL	NULL	NULL	2	Start temporary; Using join buffer (flat, BNL join)
-1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (incremental, BNL join)
-1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	5	Using where; End temporary; Using join buffer (incremental, BNL join)
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
+1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	5	Using where; Using join buffer (incremental, BNL join)
+1	PRIMARY	t4	ALL	NULL	NULL	NULL	NULL	2	Using where; Start temporary; End temporary; Using join buffer (incremental, BNL join)
 SELECT * FROM t1 NATURAL LEFT JOIN (t2, t3 ) WHERE IFNULL(t2.f3,'foo') IN (SELECT * FROM t4);
 f1	f2	f3	f3
 2	0	0	0

sql/optimizer_costs.h

@@ -75,6 +75,13 @@ static inline double cache_hit_ratio(uint ratio)
 #define ROW_COPY_COST             optimizer_row_copy_cost
 #define ROW_COPY_COST_THD(THD)    ((THD)->variables.optimizer_row_copy_cost)
 
+/*
+  Creating a record from the join cache is faster than getting a row from
+  the engine. JOIN_CACHE_ROW_COPY_COST_FACTOR is the factor used to
+  take this into account. This is multiplied with ROW_COPY_COST.
+*/
+#define JOIN_CACHE_ROW_COPY_COST_FACTOR 0.75
+
 /*
   Cost of finding the next key during index scan and copying it to
   'table->record'

sql/sql_select.cc

@@ -8786,7 +8786,8 @@ best_access_path(JOIN      *join,
       row combinations, only a HASH_FANOUT (10%) rows in the cache.
     */
     cmp_time= (rnd_records * record_count * HASH_FANOUT *
-               WHERE_COST_THD(thd));
+               (ROW_COPY_COST_THD(thd) * JOIN_CACHE_ROW_COPY_COST_FACTOR +
+                WHERE_COST_THD(thd)));
     tmp= COST_ADD(tmp, cmp_time);
 
     best_cost= tmp;
@@ -9018,7 +9019,8 @@ best_access_path(JOIN      *join,
           row.
         */
         cmp_time= (rnd_records * record_count *
-                   (ROW_COPY_COST_THD(thd) * (idx - join->const_tables) +
+                   (ROW_COPY_COST_THD(thd) * (idx - join->const_tables) *
+                    JOIN_CACHE_ROW_COPY_COST_FACTOR +
                     WHERE_COST_THD(thd)));
         tmp= COST_ADD(tmp, cmp_time);
       }