LP:849776 - Wrong result with semijoin + "Impossible where"

The following query:

select * from t5 where (a) in (
SELECT t1.a FROM t1
LEFT JOIN t2 ON ( t1.a = t2.a ) WHERE t2.b NOT IN ( SELECT t4.b FROM t4 WHERE t4.b < t1.b ));

returns no rows when executed with semijoin, even though the correct result must be "8", since table t5 contains the result from the subquery.

mysql 5.5 also wrongly returns an empty result, though the plan there is different. Postgresql confirms that the correct result is "8".

explain:

minimal optimizer_switch: semijoin=on
full optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=off,derived_merge=off,derived_with_keys=off,firstmatch=off,loosescan=off,materialization=off,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=off,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

bzr version-info:

revision-id: <email address hidden>
date: 2011-09-10 18:01:27 +0300
build-date: 2011-09-14 11:28:19 +0300
revno: 3183
branch-nick: maria-5.3

test case:

CREATE TABLE t1 ( b varchar(1), a integer) ;
INSERT INTO t1 VALUES ('z',8);

CREATE TABLE t2 ( a integer, b varchar(1)) ;

CREATE TABLE t4 ( a integer, b varchar(1)) ;

CREATE TABLE t5 ( a integer) ;
INSERT INTO t5 VALUES (8);

set session optimizer_switch='semijoin=on';
select * from t5 where (a) in (
SELECT t1.a FROM t1
LEFT JOIN t2 ON ( t1.a = t2.a ) WHERE t2.b NOT IN ( SELECT t4.b FROM t4 WHERE t4.b < t1.b ));