Fixed LP bug #939009.

The result of materialization of the right part of an IN subquery predicate
is placed into a temporary table. Each row of the materialized table is
distinct. A unique key over all fields of the temporary table is defined and
created. It allows to perform key look-ups into the table.
The table created for a materialized subquery can be accessed by key as
any other table. The function best_access-path search for the best access
to join a table to a given partial join. With some where conditions this
function considers a possibility of a ref_or_null access. If such access
employs the unique key on the temporary table then when estimating
the cost this access the function tries to use the array rec_per_key. Yet,
such array is not built for this unique key. This causes a crash of the server.

Rows returned by the subquery that contain nulls don't have to be placed
into temporary table, as they cannot be match any row produced by the
left part of the subquery predicate. So all fields of the temporary table
can be defined as non-nullable. In this case any ref_or_null access
to the temporary table does not make any sense and it does not make sense
to estimate such an access.

The fix makes sure that the temporary table for a materialized IN subquery
is defined with columns that are all non-nullable. The also ensures that 
any row with nulls returned by the subquery is not placed into the
temporary table.  

1 files changed, 7 insertions, 7 deletions

diff --git a/mysql-test/r/subselect_sj_nonmerged.result b/mysql-test/r/subselect_sj_nonmerged.result
index 8df74536de7..2a3768c8c50 100644
--- a/mysql-test/r/subselect_sj_nonmerged.result
+++ b/mysql-test/r/subselect_sj_nonmerged.result
@@ -40,14 +40,14 @@ alter table t3 add primary key(a);
 #   (despite that subquery's join output estimate is 50 rows)
 explain select * from t3 where a in (select max(t2.a) from t1, t2 group by t2.b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	5	Using where
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	5	
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	8	<subquery2>.max(t2.a)	1	Using where; Using index
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary
 2	MATERIALIZED	t1	ALL	NULL	NULL	NULL	NULL	10	Using join buffer (flat, BNL join)
 # Compare to this which really will have 50 record combinations:
 explain select * from t3 where a in (select max(t2.a) from t1, t2 group by t2.b, t1.b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	50	Using where
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	50	
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	8	<subquery2>.max(t2.a)	1	Using where; Using index
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary
 2	MATERIALIZED	t1	ALL	NULL	NULL	NULL	NULL	10	Using join buffer (flat, BNL join)
@@ -57,7 +57,7 @@ SET optimizer_switch='outer_join_with_cache=off';
 explain select * from t3 
 where a in (select max(t2.a) from t1 left join t2 on t1.a=t2.a group by t2.b, t1.b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	50	Using where
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	50	
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	8	<subquery2>.max(t2.a)	1	Using where; Using index
 2	MATERIALIZED	t1	ALL	NULL	NULL	NULL	NULL	10	Using temporary
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
@@ -69,7 +69,7 @@ t4.b=t0.a and t4.a in (select max(t2.a) from t1, t2 group by t2.b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t0	ALL	NULL	NULL	NULL	NULL	10	
 1	PRIMARY	t4	ALL	a	NULL	NULL	NULL	100	Using where; Using join buffer (flat, BNL join)
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	test.t4.a	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	test.t4.a	1	
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary
 2	MATERIALIZED	t1	ALL	NULL	NULL	NULL	NULL	10	Using join buffer (flat, BNL join)
 insert into t4 select 100 + (B.a *100 + A.a), 100 + (B.a*100 + A.a), 'filler' from t4 A, t0 B;
@@ -77,8 +77,8 @@ explain select * from t4 where
 t4.a in (select max(t2.a) from t1, t2 group by t2.b) and 
 t4.b in (select max(t2.a) from t1, t2 group by t2.b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	5	Using where
-1	PRIMARY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	5	Using where; Using join buffer (flat, BNL join)
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	5	
+1	PRIMARY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	5	Using join buffer (flat, BNL join)
 1	PRIMARY	t4	ref	a	a	10	<subquery2>.max(t2.a),<subquery3>.max(t2.a)	12	
 3	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary
 3	MATERIALIZED	t1	ALL	NULL	NULL	NULL	NULL	10	Using join buffer (flat, BNL join)
@@ -114,7 +114,7 @@ insert into t1 select A.a + 10*B.a + 100*C.a from t0 A, t0 B, t0 C;
 # The following must use non-merged SJ-Materialization:
 explain select * from t1 X join t0 Y on X.a < Y.a where X.a in (select max(a) from t0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	1	Using where
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	1	
 1	PRIMARY	X	ref	a	a	5	<subquery2>.max(a)	1	Using index
 1	PRIMARY	Y	ALL	NULL	NULL	NULL	NULL	10	Using where; Using join buffer (flat, BNL join)
 2	MATERIALIZED	t0	ALL	NULL	NULL	NULL	NULL	10