The following query:

SELECT *
FROM t1
WHERE (t1.a, t1.b) NOT IN (
SELECT t2.a, t2.b
FROM t2
);

returns no rows when executed with partial_match_rowid_merge even though the WHERE should evaluate to TRUE for all rows in t1 (as confirmed by PostgreSQL).

EXPLAIN:

id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 SUBQUERY t2 ALL NULL NULL NULL NULL 2

minimal switch: materialization=on,partial_match_rowid_merge=on,partial_match_table_scan=off
full 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=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=off,subquery_cache=on,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

reproducible on both maria-5.3 and maria-5.3-mwl89

revision-id: <email address hidden>
date: 2011-11-20 04:53:07 -0800
build-date: 2011-11-22 10:41:56 +0200
revno: 3298
branch-nick: maria-5.3

test case:

SET SESSION optimizer_switch='materialization=on,partial_match_rowid_merge=on,partial_match_table_scan=off';
CREATE TABLE t1 ( a int, b int);
INSERT INTO t1 VALUES (0,NULL),(0,NULL);

CREATE TABLE t2 (a int, b int);
INSERT INTO t2 VALUES (2,2),(2,2);

SELECT *
FROM t1
WHERE (t1.a, t1.b) NOT IN (
SELECT t2.a, t2.b
FROM t2
);