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Bug#30302: Tables that were optimized away are printed in the

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EXPLAIN EXTENDED warning.

Query optimizer searches for the constant tables and optimizes them away. This
means that fields of such tables are substituted for their values and on later
phases they are treated as constants. After this constant tables are removed
from the query execution plan. Nevertheless constant tables were shown in 
the EXPLAIN EXTENDED warning thus producing query that might be not an
equivalent of the original query.
        
Now the print_join function skips all tables that were optimized away from
printing to the EXPLAIN EXTENDED warning. If all tables were optimized away it
produces the 'FROM dual' clause.
This commit is contained in:
Evgeny Potemkin
2009-10-19 15:13:26 +04:00
parent 68c55462ef
commit 14994d2148
12 changed files with 76 additions and 22 deletions
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26
mysql-test/r/explain.result
View File

@ -64,7 +64,7 @@ explain extended select * from v1 where f2=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from `test`.`t1` where 1
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual where 1
explain extended select * from t1 where 0;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
@ -74,7 +74,7 @@ explain extended select * from t1 where 1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from `test`.`t1` where 1
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual where 1
explain extended select * from t1 having 0;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible HAVING
@ -84,7 +84,7 @@ explain extended select * from t1 having 1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from `test`.`t1` having 1
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual having 1
drop view v1;
drop table t1;
CREATE TABLE t1(c INT);
@ -194,4 +194,24 @@ dt
2001-01-01 01:01:01
2001-01-01 01:01:01
drop tables t1, t2;
#
# Bug#30302: Tables that were optimized away are printed in the
# EXPLAIN EXTENDED warning.
#
create table t1(f1 int);
create table t2(f2 int);
insert into t1 values(1);
insert into t2 values(1),(2);
explain extended select * from t1 where f1=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1` from dual where 1
explain extended select * from t1 join t2 on f1=f2 where f1=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
1 SIMPLE t2 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1003 select '1' AS `f1`,`test`.`t2`.`f2` AS `f2` from `test`.`t2` where (`test`.`t2`.`f2` = 1)
drop table t1,t2;
End of 5.1 tests.