| 2010-12-26 10:05:24 |
Philip Stoev |
description |
In maria-5.3 , the following query:
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
returns no rows even though 1 row matches the WHERE predicate and is returned by all other plans.
explain:
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
1 SIMPLE t2 ref f3 f3 5 const 1 Using where; Using join buffer (flat, BNLH join)
test case:
CREATE TABLE t1 (f2 int(11), f4 varchar(10)) ;
INSERT IGNORE INTO t1 VALUES ('19','time'),('24','juabngoyrt');
CREATE TABLE t2 (f5 varchar(10), f2 int(11), f1 int(11), f3 int(11), KEY (f3)) ;
INSERT IGNORE INTO t2 VALUES ('time','4',NULL,NULL);
SET SESSION join_cache_level=6;
SET SESSION optimizer_switch='join_cache_bka=off';
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
EXPLAIN SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
SET SESSION join_cache_level=0;
SET SESSION optimizer_switch='index_condition_pushdown=off';
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ; |
In maria-5.3 , the following query:
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
returns no rows even though 1 row matches the WHERE predicate and is returned by all other plans.
explain:
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
1 SIMPLE t2 ref f3 f3 5 const 1 Using where; Using join buffer (flat, BNLH join)
test case:
CREATE TABLE t1 (f2 int(11), f4 varchar(10)) ;
INSERT IGNORE INTO t1 VALUES ('19','time'),('24','juabngoyrt');
CREATE TABLE t2 (f5 varchar(10), f2 int(11), f1 int(11), f3 int(11), KEY (f3)) ;
INSERT IGNORE INTO t2 VALUES ('time','4',NULL,NULL);
SET SESSION join_cache_level=6;
SET SESSION optimizer_switch='join_cache_bka=off';
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
EXPLAIN SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
SET SESSION join_cache_level=0;
SET SESSION optimizer_switch='index_condition_pushdown=off';
SELECT STRAIGHT_JOIN t1.f2 FROM t1 JOIN t2 ON t1.f4 = t2.f5 WHERE ( t2.f1 OR t2.f2 ) AND t2.f3 IS NULL ;
Even though this particular test case includes join_cache_bka=off, the problematic query plan was also observed without having to force it. |
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