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The problem appeared in the 5.3 tree with the following revision:
revno: 3645 [merge]
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revision-id: igor@askmonty.org-20130327155816-ocjsyxyqgcsraf0s
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------------------------------------------------------------
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revno: 3639.1.1
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revision-id: igor@askmonty.org-20130323043306-2cteo3ndk22af921
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message:
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Fixed bug mdev-4318.
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In some cases, when using views the optimizer incorrectly determined
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possible join orders for queries with nested outer and inner joins.
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This could lead to invalid execution plans for such queries.
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With the data provided in the test case, the test query produces a result set consisting of 31 rows:
SELECT DISTINCT alias1.id
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FROM t1 AS alias1 LEFT JOIN v1 AS alias2 LEFT JOIN t2 AS alias3
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ON alias2.id = alias3.i ON alias1.i1 = alias2.i1
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WHERE alias3.i != 3;
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id
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7
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9
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18
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20
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24
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50
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51
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61
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71
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94
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97
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100
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104
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114
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119
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128
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129
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140
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8
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43
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45
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64
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74
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77
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78
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93
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101
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107
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132
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133
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156
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However, a similar query with an extended select list (but the same joins and WHERE clause) produces 32 rows:
SELECT DISTINCT alias1.id, alias2.id, alias3.i, alias1.i1, alias2.i1
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FROM t1 AS alias1 LEFT JOIN v1 AS alias2 LEFT JOIN t2 AS alias3
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ON alias2.id = alias3.i ON alias1.i1 = alias2.i1
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WHERE alias3.i != 3;
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id id i i1 i1
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7 7 7 6 6
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9 7 7 6 6
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18 7 7 6 6
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20 7 7 6 6
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24 7 7 6 6
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50 7 7 6 6
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51 7 7 6 6
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61 7 7 6 6
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71 7 7 6 6
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94 7 7 6 6
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97 7 7 6 6
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100 7 7 6 6
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104 7 7 6 6
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114 7 7 6 6
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119 7 7 6 6
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128 7 7 6 6
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129 7 7 6 6
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140 7 7 6 6
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8 8 8 3 3
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43 8 8 3 3
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45 8 8 3 3
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64 8 8 3 3
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74 8 8 3 3
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77 8 8 3 3
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78 8 8 3 3
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93 8 8 3 3
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101 8 8 3 3
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107 8 8 3 3
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132 8 8 3 3
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133 8 8 3 3
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156 7 7 6 6
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151 8 8 3 3
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The last row, with alias1.id=151, is missing from the first list. It seems to satisfy the condition, so I presume 32 rows is the correct result and 31 rows is not.
SELECT COUNT and other variations of the query also return 32 rows. With join_cache_level=0, the initial query also returns 32 rows.
Test case:
CREATE TABLE t1 (
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id INT,
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i1 INT,
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i2 INT DEFAULT 0,
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d1 DATE DEFAULT '2000-01-01',
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d2 DATE DEFAULT '2000-01-01',
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t1 TIME DEFAULT '00:00:00',
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t2 TIME DEFAULT '00:00:00',
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dt1 DATETIME NOT NULL DEFAULT '2000-01-01 00:00:00',
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dt2 DATETIME NOT NULL DEFAULT '2000-01-01 00:00:00',
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c1 VARCHAR(1) NOT NULL,
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c2 VARCHAR(1) NOT NULL
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) ENGINE=MyISAM;
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CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
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INSERT INTO t1 (id,i1,c1,c2) VALUES
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(1,7,'t','t'),(2,4,'k','k'),(3,2,'e','e'),(4,0,'i','i'),(5,1,'t','t'),(6,91,'m','m'),(7,6,'z','z'),(8,3,'c','c'),(9,6,'i','i'),(10,8,'v','v'),
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(11,1,'l','l'),(12,4,'j','j'),(13,5,'w','w'),(14,0,'r','r'),(15,7,'o','o'),(16,9,'o','o'),(17,7,'u','u'),(18,6,'f','f'),(19,0,'l','l'),(20,6,'g','g'),
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(21,1,'e','e'),(22,7,'y','y'),(23,0,'p','p'),(24,6,'v','v'),(25,5,'d','d'),(26,9,'i','i'),(27,5,'z','z'),(28,2,'q','q'),(29,4,'j','j'),(30,9,'m','m'),
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(31,8,'d','d'),(32,5,'r','r'),(33,1,'r','r'),(34,1,'k','k'),(35,4,'p','p'),(36,2,'x','x'),(37,5,'w','w'),(38,0,'k','k'),(39,7,'y','y'),(40,4,'p','p'),
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(41,9,'l','l'),(42,2,'u','u'),(43,3,'r','r'),(44,5,'y','y'),(45,3,'u','u'),(46,9,'t','t'),(47,8,'f','f'),(48,2,'f','f'),(49,2,'q','q'),(50,6,'v','v'),
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(51,6,'u','u'),(52,0,'b','b'),(53,1,'n','n'),(54,2,'p','p'),(55,0,'y','y'),(56,1,'l','l'),(57,1,'c','c'),(58,0,'d','d'),(59,2,'y','y'),(60,7,'l','l'),
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(61,6,'m','m'),(62,9,'q','q'),(63,0,'j','j'),(64,3,'u','u'),(65,4,'w','w'),(66,5,'p','p'),(67,8,'z','z'),(68,5,'u','u'),(69,7,'b','b'),(70,0,'f','f'),
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(71,6,'u','u'),(72,1,'i','i'),(73,9,'s','s'),(74,3,'y','y'),(75,5,'s','s'),(76,8,'x','x'),(77,3,'s','s'),(78,3,'l','l'),(79,8,'b','b'),(80,0,'p','p'),
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(81,9,'m','m'),(82,5,'k','k'),(83,7,'u','u'),(84,0,'y','y'),(85,2,'x','x'),(86,5,'h','h'),(87,5,'j','j'),(88,5,'o','o'),(89,9,'o','o'),(90,1,'c','c'),
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(91,7,'k','k'),(92,9,'t','t'),(93,3,'h','h'),(94,6,'g','g'),(95,9,'r','r'),(96,2,'i','i'),(97,6,'l','l'),(98,4,'a','a'),(99,9,'w','w'),(100,6,'n','n'),
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(101,3,'c','c'),(102,1,'a','a'),(103,9,'z','z'),(104,6,'k','k'),(105,7,'a','a'),(106,7,'g','g'),(107,3,'k','k'),(108,8,'h','h'),(109,7,'y','y'),(110,1,'d','d'),
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(111,0,'p','p'),(112,4,'b','b'),(113,2,'n','n'),(114,6,'l','l'),(115,0,'s','s'),(116,0,'n','n'),(117,8,'o','o'),(118,9,'f','f'),(119,6,'u','u'),(120,1,'j','j'),
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(121,1,'q','q'),(122,8,'y','y'),(123,1,'c','c'),(124,17,'i','i'),(125,1,'v','v'),(126,0,'w','w'),(127,5,'q','q'),(128,6,'n','n'),(129,6,'x','x'),(130,2,'b','b'),
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(131,8,'l','l'),(132,3,'i','i'),(133,3,'d','d'),(134,7,'h','h'),(135,0,'i','i'),(136,1,'n','n'),(137,2,'g','g'),(138,7,'u','u'),(139,0,'d','d'),(140,6,'x','x'),
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(141,1,'a','a'),(142,0,'q','q'),(143,9,'n','n'),(144,8,'r','r'),(145,4,'r','r'),(146,4,'g','g'),(147,0,'u','u'),(148,1,'j','j'),(149,0,'m','m'),(150,4,'u','u'),
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(151,3,'m','m'),(152,9,'p','p'),(153,1,'o','o'),(154,8,'v','v'),(155,9,'f','f'),(156,6,'f','f'),(157,1,'e','e'),(158,5,'l','l'),(159,8,'j','j');
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CREATE TABLE t2 (i INT) ENGINE=MyISAM;
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INSERT INTO t2 VALUES (7),(8);
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SELECT DISTINCT alias1.id
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FROM t1 AS alias1 LEFT JOIN v1 AS alias2 LEFT JOIN t2 AS alias3
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ON alias2.id = alias3.i ON alias1.i1 = alias2.i1
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WHERE alias3.i != 3;
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EXPLAIN:
EXPLAIN EXTENDED
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SELECT DISTINCT alias1.id FROM t1 AS alias1 LEFT JOIN v1 AS alias2 LEFT JOIN t2 AS alias3
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ON alias2.id = alias3.i ON alias1.i1 = alias2.i1
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WHERE alias3.i != 3;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 PRIMARY alias1 ALL NULL NULL NULL NULL 159 100.00 Using where; Using temporary
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1 PRIMARY <derived2> ref key0 key0 5 test.alias1.i1 10 100.00 Using where; Distinct
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1 PRIMARY alias3 ALL NULL NULL NULL NULL 2 100.00 Using where; Distinct; Using join buffer (flat, BNL join)
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2 DERIVED t1 ALL NULL NULL NULL NULL 159 100.00
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Warnings:
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Note 1003 select distinct `test`.`alias1`.`id` AS `id` from `test`.`t1` `alias1` join `test`.`v1` `alias2` join `test`.`t2` `alias3` where ((`test`.`alias3`.`i` = `alias2`.`id`) and (`alias2`.`i1` = `test`.`alias1`.`i1`) and (`alias2`.`id` <> 3))
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