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b3e70bde38This is done by no longer merging inner table dep with outer nested_join ones. This expands the search space of outer joins and introduces suboptimal join order choices already existing in inner joins (e.g. MDEV-36331, MDEV-37346) to outer joins, caused by heuristic pruning. To mitigate this issue, we add a switch that turns on heuristic pruning always (existing behaviour), and make is so that when the switch is off (default) joins with limited number of tables or limited search space* do not perform heuristic pruning. This improves join order optimization for these joins, where otherwise heuristic pruning may remove good joins - see added test cases in the test main.greedy_optimizer. *: about the same as 10 tables with default search depth (7) when optimizer_search_depth=0. If we completely disable heuristic pruning, or use the upper bound 10!, the test main.greedy_optimizer will grind to almost hanging for optimizer_search_depth=0 when more than 20 tables are involved. If we only compare the number of tables with 10, then it will prune when search space is low due to a low search depth when we can afford not to prune.
65 lines
2.5 KiB
Text
65 lines
2.5 KiB
Text
CREATE TABLE t1 (
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pk INT,
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f1 VARCHAR(10) NOT NULL,
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f2 VARCHAR(10) NULL,
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f3 INT UNSIGNED NULL,
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KEY (f1),
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PRIMARY KEY (pk)
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) ENGINE=InnoDB;
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CREATE OR REPLACE ALGORITHM=MERGE VIEW v4 AS SELECT * FROM t1;
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INSERT INTO t1 VALUES (1,'k','g',6),(2,'y','r',0),(3,'t','q',1),(4,'a','r',NULL),(5,'z','t',NULL);
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CREATE TABLE t2 (f VARCHAR(10) NULL) ENGINE=InnoDB;
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INSERT INTO t2 VALUES (NULL),('g'),('e'),('g');
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CREATE TABLE t3 (
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f1 VARCHAR(10) NOT NULL,
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f2 VARCHAR(10) NULL,
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f3 INT UNSIGNED NULL
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) ENGINE=InnoDB;
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INSERT INTO t3 VALUES ('k','n',9),('y','b',8),('m','w',6);
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CREATE TABLE t4 (f INT NULL) ENGINE=InnoDB;
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INSERT INTO t4 VALUES (8),(9);
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UPDATE t1 SET t1.pk = -109 WHERE t1.f1 IN ( SELECT 'a' FROM t4 WHERE f >= 1 );
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SET DEBUG_SYNC='now SIGNAL con1_dml';
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connect con1,localhost,root,,test;
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SET DEBUG_SYNC='now WAIT_FOR con1_dml';
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begin;
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SELECT * FROM t1 for update;
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pk f1 f2 f3
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-109 a r NULL
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1 k g 6
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2 y r 0
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3 t q 1
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5 z t NULL
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SET DEBUG_SYNC='now SIGNAL default_dml';
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SET DEBUG_SYNC='now SIGNAL con2_dml';
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connection default;
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SET DEBUG_SYNC='now WAIT_FOR default_dml';
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explain UPDATE t3 AS alias1 LEFT JOIN t3 AS alias2 ON ( alias1.f1 <> alias1.f2 ) SET alias1.f3 = 59 WHERE ( EXISTS ( SELECT t1.f3 FROM t1 IGNORE INDEX (f1) WHERE t1.f1 = alias1.f1 ) ) OR alias2.f1 = 'h';
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY alias1 ALL NULL NULL NULL NULL #
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1 PRIMARY alias2 ALL NULL NULL NULL NULL # Using where
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2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL # Using where
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UPDATE t3 AS alias1 LEFT JOIN t3 AS alias2 ON ( alias1.f1 <> alias1.f2 ) SET alias1.f3 = 59 WHERE ( EXISTS ( SELECT t1.f3 FROM t1 IGNORE INDEX (f1) WHERE t1.f1 = alias1.f1 ) ) OR alias2.f1 = 'h';
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connect con2,localhost,root,,test;
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set debug_sync='now WAIT_FOR con2_dml';
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SET DEBUG_SYNC='now SIGNAL con1_dml2';
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disconnect con2;
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connection con1;
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SET DEBUG_SYNC='now WAIT_FOR con1_dml2';
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explain UPDATE v4, t1 SET t1.pk = 76 WHERE t1.f2 IN ( SELECT t2.f FROM t2 INNER JOIN t3 );
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 ALL NULL NULL NULL NULL #
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1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 43 func #
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1 PRIMARY t1 index NULL f1 42 NULL # Using index
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2 MATERIALIZED t3 ALL NULL NULL NULL NULL #
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2 MATERIALIZED t2 ALL NULL NULL NULL NULL #
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UPDATE v4, t1 SET t1.pk = 76 WHERE t1.f2 IN ( SELECT t2.f FROM t2 INNER JOIN t3 );
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ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
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connection default;
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connection con1;
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COMMIT;
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disconnect con1;
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connection default;
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DROP VIEW v4;
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DROP TABLE t1, t2, t3, t4;
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set debug_sync= reset;
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