Added keyread_time() to HEAP

The default keyread_time() was optimized for blocks and not suitable for
HEAP. The effect was the HEAP prefered table scans over ranges for btree
indexes.
Fixed also get_sweep_read_cost() for HEAP tables.

mysql-test/suite/heap/heap_btree.result

@@ -178,7 +178,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	btn	btn	10	NULL	1	Using where
 explain select * from t1 where btn like "h%";
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	#	Using where
+1	SIMPLE	t1	range	btn	btn	10	NULL	#	Using where
 explain select * from t1 where btn like "a%";
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	btn	btn	10	NULL	1	Using where

mysql-test/suite/heap/heap_hash.result

@@ -428,14 +428,14 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	uniq_id	uniq_id	8	NULL	2	Using where
 select 0+a from t1 where a in (869751,736494,226312,802616,728912);
 0+a
-869751
-736494
 226312
-802616
 728912
+736494
+802616
+869751
 explain select 0+a from t1 where a in (869751,736494,226312,802616,728912);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	uniq_id	NULL	NULL	NULL	5	Using where
+1	SIMPLE	t1	range	uniq_id	uniq_id	8	NULL	5	Using where
 drop table t1;
 End of 5.3 tests
 #

sql/handler.cc

@@ -2675,11 +2675,13 @@ double handler::keyread_time(uint index, uint ranges, ha_rows rows)
   size_t len= table->key_info[index].key_length + ref_length;
   if (index == table->s->primary_key && table->file->primary_key_is_clustered())
     len= table->s->stored_rec_length;
-  uint keys_per_block= (uint) (stats.block_size/2.0/len+1);
-  ulonglong blocks= !rows ? 0 : (rows-1) / keys_per_block + 1;
   double cost= (double)rows*len/(stats.block_size+1)*IDX_BLOCK_COPY_COST;
   if (ranges)
+  {
+    uint keys_per_block= (uint) (stats.block_size/2.0/len+1);
+    ulonglong blocks= !rows ? 0 : (rows-1) / keys_per_block + 1;
     cost+= blocks;
+  }
   return cost;
 }
 

sql/opt_range.cc

@@ -4897,7 +4897,8 @@ double get_sweep_read_cost(const PARAM *param, ha_rows records)
 {
   double result;
   DBUG_ENTER("get_sweep_read_cost");
-  if (param->table->file->primary_key_is_clustered())
+  if (param->table->file->primary_key_is_clustered() ||
+      param->table->file->stats.block_size == 0 /* HEAP */)
   {
     /*
       We are using the primary key to find the rows.

storage/heap/ha_heap.h

@@ -66,7 +66,8 @@ class ha_heap: public handler
   { return (double) (stats.records+stats.deleted) / 20.0+10; }
   double read_time(uint index, uint ranges, ha_rows rows)
   { return (double) rows / 20.0+1; }
-
+  double keyread_time(uint index, uint ranges, ha_rows rows)
+  { return (double) rows / 20.0+1; }
   int open(const char *name, int mode, uint test_if_locked);
   int close(void);
   void set_keys_for_scanning(void);