Fix for bug#5138: hash indexes on heap tables support statistics.

 KEY::rec_per_key is updated every time 1/HEAP_STATS_UPDATE_THRESHOLD part of table records has been changed.


heap/_check.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
heap/hp_clear.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
heap/hp_create.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
heap/hp_delete.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
heap/hp_hash.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
heap/hp_write.c:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
include/heap.h:
  Hash indexes on heap tables now support statistics - number of hash buckets. The value is updated on any insert/delete operation.
mysql-test/r/heap.result:
  Fix for bug#5138: store/use statistics for hash indexes on heap tables
mysql-test/r/heap_hash.result:
  Fix for bug#5138: store/use statistics for hash indexes on heap tables
mysql-test/r/myisam.result:
  Fix for bug#5138: store/use statistics for hash indexes on heap tables
mysql-test/t/heap_hash.test:
  Fix for bug#5138: store/use statistics for hash indexes on heap tables
sql/structs.h:
  Added comments

4 files changed, 248 insertions, 10 deletions

diff --git a/mysql-test/r/heap.result b/mysql-test/r/heap.result
index c49c9abb368..f4ee11fe1a3 100644
--- a/mysql-test/r/heap.result
+++ b/mysql-test/r/heap.result
@@ -4,7 +4,7 @@ insert into t1 values(1,1),(2,2),(3,3),(4,4);
 delete from t1 where a=1 or a=0;
 show keys from t1;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
-t1	0	PRIMARY	1	a	NULL	NULL	NULL	NULL		HASH	
+t1	0	PRIMARY	1	a	NULL	3	NULL	NULL		HASH	
 select * from t1;
 a	b
 2	2
@@ -169,7 +169,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	11	Using where
 explain select * from t1 where btn="a" and new_col="a";
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	btn	btn	11	const,const	10	Using where
+1	SIMPLE	t1	ref	btn	btn	11	const,const	2	Using where
 drop table t1;
 CREATE TABLE t1 (
 a int default NULL,
@@ -182,7 +182,7 @@ SELECT * FROM t1 WHERE a=NULL;
 a	b
 explain SELECT * FROM t1 WHERE a IS NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a	a	5	const	10	Using where
+1	SIMPLE	t1	ref	a	a	5	const	1	Using where
 SELECT * FROM t1 WHERE a<=>NULL;
 a	b
 NULL	99
@@ -204,7 +204,7 @@ key a (a)
 INSERT INTO t1 VALUES (10), (10), (10);
 EXPLAIN SELECT * FROM t1 WHERE a=10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a	a	5	const	10	Using where
+1	SIMPLE	t1	ref	a	a	5	const	3	Using where
 SELECT * FROM t1 WHERE a=10;
 a
 10
diff --git a/mysql-test/r/heap_hash.result b/mysql-test/r/heap_hash.result
index 7affbf788fb..29287b23745 100644
--- a/mysql-test/r/heap_hash.result
+++ b/mysql-test/r/heap_hash.result
@@ -1,10 +1,10 @@
-drop table if exists t1;
+drop table if exists t1,t2;
 create table t1 (a int not null,b int not null, primary key using HASH (a)) engine=heap comment="testing heaps" avg_row_length=100 min_rows=1 max_rows=100;
 insert into t1 values(1,1),(2,2),(3,3),(4,4);
 delete from t1 where a=1 or a=0;
 show keys from t1;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
-t1	0	PRIMARY	1	a	NULL	NULL	NULL	NULL		HASH	
+t1	0	PRIMARY	1	a	NULL	3	NULL	NULL		HASH	
 select * from t1;
 a	b
 2	2
@@ -169,7 +169,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	11	Using where
 explain select * from t1 where btn="a" and new_col="a";
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	btn	btn	11	const,const	10	Using where
+1	SIMPLE	t1	ref	btn	btn	11	const,const	2	Using where
 drop table t1;
 CREATE TABLE t1 (
 a int default NULL,
@@ -182,7 +182,7 @@ SELECT * FROM t1 WHERE a=NULL;
 a	b
 explain SELECT * FROM t1 WHERE a IS NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a	a	5	const	10	Using where
+1	SIMPLE	t1	ref	a	a	5	const	1	Using where
 SELECT * FROM t1 WHERE a<=>NULL;
 a	b
 NULL	99
@@ -203,3 +203,139 @@ DELETE from t1 where a < 100;
 SELECT * from t1;
 a
 DROP TABLE t1;
+create table t1
+(
+a char(8) not null,
+b char(20) not null,
+c int not null,
+key (a)
+) engine=heap;
+insert into t1 values ('aaaa', 'prefill-hash=5',0);
+insert into t1 values ('aaab', 'prefill-hash=0',0);
+insert into t1 values ('aaac', 'prefill-hash=7',0);
+insert into t1 values ('aaad', 'prefill-hash=2',0);
+insert into t1 values ('aaae', 'prefill-hash=1',0);
+insert into t1 values ('aaaf', 'prefill-hash=4',0);
+insert into t1 values ('aaag', 'prefill-hash=3',0);
+insert into t1 values ('aaah', 'prefill-hash=6',0);
+explain select * from t1 where a='aaaa';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	1	Using where
+explain select * from t1 where a='aaab';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	1	Using where
+explain select * from t1 where a='aaac';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	1	Using where
+explain select * from t1 where a='aaad';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	1	Using where
+insert into t1 select * from t1;
+explain select * from t1 where a='aaaa';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaab';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaac';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaad';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+create table t2 as select * from t1;
+delete from t1;
+insert into t1 select * from t2;
+explain select * from t1 where a='aaaa';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaab';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaac';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+explain select * from t1 where a='aaad';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a	a	8	const	2	Using where
+drop table t1, t2;
+create table t1 (
+id int unsigned not null primary key auto_increment, 
+name varchar(20) not null,
+index heap_idx(name),
+index btree_idx using btree(name)
+) engine=heap;
+create table t2 (
+id int unsigned not null primary key auto_increment, 
+name varchar(20) not null,
+index btree_idx using btree(name),
+index heap_idx(name)
+) engine=heap;
+insert into t1 (name) values ('Matt'), ('Lilu'), ('Corbin'), ('Carly'), 
+('Suzy'), ('Hoppy'), ('Burrito'), ('Mimi'), ('Sherry'), ('Ben'), ('Phil'), 
+('Emily'), ('Mike');
+insert into t2 select * from t1;
+explain select * from t1 where name='matt';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	heap_idx,btree_idx	heap_idx	20	const	1	Using where
+explain select * from t2 where name='matt';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ref	btree_idx,heap_idx	btree_idx	20	const	1	Using where
+explain select * from t1 where name='Lilu';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	heap_idx,btree_idx	heap_idx	20	const	1	Using where
+explain select * from t2 where name='Lilu';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ref	btree_idx,heap_idx	btree_idx	20	const	1	Using where
+explain select * from t1 where name='Phil';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	heap_idx,btree_idx	heap_idx	20	const	1	Using where
+explain select * from t2 where name='Phil';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ref	btree_idx,heap_idx	btree_idx	20	const	1	Using where
+explain select * from t1 where name='Lilu';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	heap_idx,btree_idx	heap_idx	20	const	1	Using where
+explain select * from t2 where name='Lilu';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ref	btree_idx,heap_idx	btree_idx	20	const	1	Using where
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+select count(*) from t1 where name='Matt';
+count(*)
+7
+explain select * from t1 ignore index (btree_idx) where name='matt';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	heap_idx	heap_idx	20	const	7	Using where
+show index from t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
+t1	0	PRIMARY	1	id	NULL	91	NULL	NULL		HASH	
+t1	1	heap_idx	1	name	NULL	15	NULL	NULL		HASH	
+t1	1	btree_idx	1	name	A	NULL	NULL	NULL		BTREE	
+flush tables;
+show index from t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
+t1	0	PRIMARY	1	id	NULL	91	NULL	NULL		HASH	
+t1	1	heap_idx	1	name	NULL	13	NULL	NULL		HASH	
+t1	1	btree_idx	1	name	A	NULL	NULL	NULL		BTREE	
+create table t3
+(
+a varchar(20) not null,
+b varchar(20) not null,
+key (a,b)
+) engine=heap;
+insert into t3 select name, name from t1;
+show index from t3;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
+t3	1	a	1	a	NULL	NULL	NULL	NULL		HASH	
+t3	1	a	2	b	NULL	15	NULL	NULL		HASH	
+flush tables;
+show index from t3;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
+t3	1	a	1	a	NULL	NULL	NULL	NULL		HASH	
+t3	1	a	2	b	NULL	13	NULL	NULL		HASH	
+drop table t1,t2;
diff --git a/mysql-test/r/myisam.result b/mysql-test/r/myisam.result
index 26dcce43d08..31b14f9b822 100644
--- a/mysql-test/r/myisam.result
+++ b/mysql-test/r/myisam.result
@@ -543,7 +543,7 @@ Warnings:
 Note	1031	Table storage engine for 't1' doesn't have this option
 show keys from t1;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
-t1	1	a	1	a	NULL	NULL	NULL	NULL	YES	HASH	
+t1	1	a	1	a	NULL	1000	NULL	NULL	YES	HASH	
 drop table t1,t2;
 create table t1 ( a tinytext, b char(1), index idx (a(1),b) );
 insert into t1 values (null,''), (null,'');
diff --git a/mysql-test/t/heap_hash.test b/mysql-test/t/heap_hash.test
index 412b6f2e705..df233633840 100644
--- a/mysql-test/t/heap_hash.test
+++ b/mysql-test/t/heap_hash.test
@@ -3,7 +3,7 @@
 #
 
 --disable_warnings
-drop table if exists t1;
+drop table if exists t1,t2;
 --enable_warnings
 
 create table t1 (a int not null,b int not null, primary key using HASH (a)) engine=heap comment="testing heaps" avg_row_length=100 min_rows=1 max_rows=100;
@@ -141,3 +141,105 @@ INSERT into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11);
 DELETE from t1 where a < 100;
 SELECT * from t1;
 DROP TABLE t1;
+
+
+#
+# Hash index # records estimate test
+#
+create table t1
+(
+  a char(8) not null,
+  b char(20) not null,
+  c int not null,
+  key (a)
+) engine=heap;
+
+insert into t1 values ('aaaa', 'prefill-hash=5',0);
+insert into t1 values ('aaab', 'prefill-hash=0',0);
+insert into t1 values ('aaac', 'prefill-hash=7',0);
+insert into t1 values ('aaad', 'prefill-hash=2',0);
+insert into t1 values ('aaae', 'prefill-hash=1',0);
+insert into t1 values ('aaaf', 'prefill-hash=4',0);
+insert into t1 values ('aaag', 'prefill-hash=3',0);
+insert into t1 values ('aaah', 'prefill-hash=6',0);
+
+explain select * from t1 where a='aaaa';
+explain select * from t1 where a='aaab';
+explain select * from t1 where a='aaac';
+explain select * from t1 where a='aaad';
+insert into t1 select * from t1;
+explain select * from t1 where a='aaaa';
+explain select * from t1 where a='aaab';
+explain select * from t1 where a='aaac';
+explain select * from t1 where a='aaad';
+
+# Check if delete_all_rows() updates #hash_buckets
+create table t2 as select * from t1;
+delete from t1;
+insert into t1 select * from t2;
+explain select * from t1 where a='aaaa';
+explain select * from t1 where a='aaab';
+explain select * from t1 where a='aaac';
+explain select * from t1 where a='aaad';
+drop table t1, t2;
+
+
+# Btree and hash index use costs. 
+create table t1 (
+  id int unsigned not null primary key auto_increment, 
+  name varchar(20) not null,
+  index heap_idx(name),
+  index btree_idx using btree(name)
+) engine=heap;
+
+create table t2 (
+  id int unsigned not null primary key auto_increment, 
+  name varchar(20) not null,
+  index btree_idx using btree(name),
+  index heap_idx(name)
+) engine=heap;
+
+insert into t1 (name) values ('Matt'), ('Lilu'), ('Corbin'), ('Carly'), 
+  ('Suzy'), ('Hoppy'), ('Burrito'), ('Mimi'), ('Sherry'), ('Ben'), ('Phil'), 
+  ('Emily'), ('Mike');
+insert into t2 select * from t1;
+
+explain select * from t1 where name='matt';
+explain select * from t2 where name='matt';
+
+explain select * from t1 where name='Lilu';
+explain select * from t2 where name='Lilu';
+
+explain select * from t1 where name='Phil';
+explain select * from t2 where name='Phil';
+
+explain select * from t1 where name='Lilu';
+explain select * from t2 where name='Lilu';
+
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+insert into t1 (name) select name from t2;
+
+select count(*) from t1 where name='Matt';
+explain select * from t1 ignore index (btree_idx) where name='matt';
+show index from t1;
+
+flush tables;
+show index from t1;
+
+create table t3
+(
+  a varchar(20) not null,
+  b varchar(20) not null,
+  key (a,b)
+) engine=heap;
+insert into t3 select name, name from t1;
+show index from t3;
+flush tables;
+show index from t3;
+
+drop table t1,t2;
+