make the heap.heap test portable

in HEAP btree indexes, the address of a record in memory is part of the
key. So, when inserting many identical keys, the actual btree
shape is defined by how and where records in memory are allocated.

records_in_range uses floats to estimate the size of the chunk of the
btree between min and max records, it depends on the btree shape and,
thus, is not portable either. As are optimizer decisions that are based
on records_in_range estimations, if the number happens to be close
to a tipping point.

as a fix, reduce the number of matching rows, so that even with
system-specific variations the optimizer would still pick the
expected plan.

Fixes heap.heap failure (range vs ALL) on ppc64

mysql-test/suite/heap/heap.result

@@ -563,32 +563,32 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=MEMORY DEFAULT CHARSET=latin1
 select count(*) from t1;
 count(*)
-270
+267
 insert into t1 values(concat('a',char(1)),concat('a',char(1)),concat('a',char(1)));
 select count(*) from t1 where v='a';
 count(*)
-10
+7
 select count(*) from t1 where c='a';
 count(*)
-10
+7
 select count(*) from t1 where t='a';
 count(*)
-10
+7
 select count(*) from t1 where v='a  ';
 count(*)
-10
+7
 select count(*) from t1 where c='a  ';
 count(*)
-10
+7
 select count(*) from t1 where t='a  ';
 count(*)
-10
+7
 select count(*) from t1 where v between 'a' and 'a ';
 count(*)
-10
+7
 select count(*) from t1 where v between 'a' and 'a ' and v between 'a  ' and 'b\n';
 count(*)
-10
+7
 explain select count(*) from t1 where v='a  ';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	v	v	13	const	#	Using where
@@ -618,9 +618,6 @@ qq
 *a    *a*a    *
 *a     *a*a     *
 *a      *a*a      *
-*a       *a*a       *
-*a        *a*a        *
-*a         *a*a         *
 explain select * from t1 where v='a';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	v	v	13	const	#	Using where

mysql-test/suite/heap/heap.test

@@ -337,6 +337,7 @@ while ($1)
   }
   dec $1;
 }
+delete from t1 where v like 'a%' and length(v) > 7;
 commit;
 --enable_query_log
 select count(*) from t1;