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, 5 insertions, 5 deletions

diff --git a/mysql-test/r/subselect_sj2.result b/mysql-test/r/subselect_sj2.result
index 4e9672446a3..1ee01030b4b 100644
--- a/mysql-test/r/subselect_sj2.result
+++ b/mysql-test/r/subselect_sj2.result
@@ -183,7 +183,7 @@ a, mid(filler1, 1,10), length(filler1)=length(filler2)
 from t2 ot where a in (select a from t1 it);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	ot	ALL	NULL	NULL	NULL	NULL	22	
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
 2	MATERIALIZED	it	ALL	NULL	NULL	NULL	NULL	32	
 select 
 a, mid(filler1, 1,10), length(filler1)=length(filler2) 
@@ -251,7 +251,7 @@ a, mid(filler1, 1,10), length(filler1)=length(filler2)
 from t2 ot where a in (select a from t1 it);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	ot	ALL	NULL	NULL	NULL	NULL	22	
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
 2	MATERIALIZED	it	ALL	NULL	NULL	NULL	NULL	52	
 select 
 a, mid(filler1, 1,10), length(filler1)=length(filler2) 
@@ -292,7 +292,7 @@ from t0 where a in
 (select t2.a+t3.a from t1 left join (t2 join t3) on t2.a=t1.a and t3.a=t1.a);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t0	ALL	NULL	NULL	NULL	NULL	10	
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	9	func	1	Using where
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	8	func	1	Using where
 2	MATERIALIZED	t1	index	a	a	5	NULL	10	Using where; Using index
 2	MATERIALIZED	t2	ref	a	a	5	test.t1.a	1	Using index
 2	MATERIALIZED	t3	ref	a	a	5	test.t1.a	1	Using index
@@ -721,7 +721,7 @@ The following must use loose index scan over t3, key a:
 explain select count(a) from t2 where a in ( SELECT  a FROM t3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	index	a	a	5	NULL	1000	Using index
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
 2	MATERIALIZED	t3	index	a	a	5	NULL	30000	Using index
 select count(a) from t2 where a in ( SELECT  a FROM t3);
 count(a)
@@ -878,7 +878,7 @@ SELECT * FROM t3 LEFT JOIN (v1,t2) ON t3.a = t2.a
 WHERE t3.b IN (SELECT b FROM t4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	1	
-1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	1	Using where
 1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	2	
 2	MATERIALIZED	t4	ALL	NULL	NULL	NULL	NULL	2