Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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None
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None
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None
Description
If the following query:
SELECT * FROM t1 RIGHT JOIN v2 ON ( v2.a = t1.a ) WHERE v2.b IN ( SELECT b FROM t3 ) AND t1.b IS NULL ;
is run without semijoin, it returns no rows whereas if a base table is used insted of the view, the query returns:
------------------+
| a | b | a | b |
------------------+
| NULL | NULL | 1 | 0 |
| NULL | NULL | 1 | 0 |
------------------+
explain:
MariaDB [test]> explain SELECT * FROM t1 RIGHT JOIN v2 ON ( v2.a = t1.a ) WHERE v2.b IN ( SELECT b FROM t3 ) AND t1.b IS NULL ;
--------------------------------------------------------------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
--------------------------------------------------------------------------------------------------------------+
| 1 | PRIMARY | t1 | ALL | NULL | NULL | NULL | NULL | 2 | Using where |
| 1 | PRIMARY | t2 | ALL | NULL | NULL | NULL | NULL | 2 | Using where; Using join buffer (flat, BNL join) |
| 2 | DEPENDENT SUBQUERY | t3 | ALL | NULL | NULL | NULL | NULL | 2 | Using where |
--------------------------------------------------------------------------------------------------------------+
minimal optimizer_switch=semijoin=off;
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=off,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
test case:
CREATE TABLE t1 ( a int, b int );
INSERT INTO t1 VALUES (0,0),(0,0);
CREATE TABLE t2 ( a int, b int );
INSERT IGNORE INTO t2 VALUES (1,0),(1,0);
CREATE TABLE t3 ( b int );
INSERT IGNORE INTO t3 VALUES (0),(0);
CREATE OR REPLACE VIEW v2 AS SELECT * FROM t2;
SELECT * FROM t1 RIGHT JOIN v2 ON ( v2.a = t1.a ) WHERE v2.b IN ( SELECT b FROM t3 ) AND t1.b IS NULL ;
Repeatable in maria-5.3. Not repeatable in maria-5.2,mysql-5.5