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96e092dc73
WL#2474 "Multi Range Read: Change the default MRR implementation to implement new MRR interface"
WL#2475 "Batched range read functions for MyISAM/InnoDb"
"Index condition pushdown for MyISAM/InnoDB"
Igor's fix from sp1r-igor@olga.mysql.com-20080330055902-07614:
There could be observed the following problems:
1. EXPLAIN did not mention pushdown conditions from on expressions in the
'extra' column. As a result if a query had no where conditions pushed
down to a table, but had on conditions pushed to this table the 'extra'
column in the EXPLAIN for the table missed 'using where'.
2. Conditions for ref access were not eliminated from on expressions
though such conditions were eliminated from the where condition.
19 lines
894 B
Text
19 lines
894 B
Text
CREATE TABLE t1 (id int(11) NOT NULL PRIMARY KEY, name varchar(20),
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INDEX (name)) ENGINE=InnoDB;
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CREATE TABLE t2 (id int(11) NOT NULL PRIMARY KEY, fkey int(11),
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FOREIGN KEY (fkey) REFERENCES t2(id)) ENGINE=InnoDB;
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INSERT INTO t1 VALUES (1,'A1'),(2,'A2'),(3,'B');
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INSERT INTO t2 VALUES (1,1),(2,2),(3,2),(4,3),(5,3);
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EXPLAIN
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SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id
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WHERE t1.name LIKE 'A%';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index PRIMARY,name name 23 NULL 3 Using where; Using index
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1 SIMPLE t2 ref fkey fkey 5 test.t1.id 1 Using index
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EXPLAIN
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SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id
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WHERE t1.name LIKE 'A%' OR FALSE;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 index NULL fkey 5 NULL 5 Using index
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.fkey 1 Using where
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DROP TABLE t1,t2;
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