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MWL#17: Table elimination

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- add debug tests (were accidentally not pushed with the bulk of WL)
This commit is contained in:
Sergey Petrunya
2009-10-29 20:50:33 +03:00
parent 664fa25e0e
commit 1d13500373
2 changed files with 49 additions and 0 deletions
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22
mysql-test/r/table_elim_debug.result Normal file
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drop table if exists t1, t2;
create table t1 (a int);
insert into t1 values (0),(1),(2),(3);
create table t2 (a int primary key, b int)
as select a, a as b from t1 where a in (1,2);
explain select t1.a from t1 left join t2 on t2.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
set optimizer_switch='table_elimination=off';
explain select t1.a from t1 left join t2 on t2.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
1 SIMPLE t2 eq_ref PRIMARY PRIMARY 4 test.t1.a 1 Using index
set optimizer_switch='table_elimination=on';
explain select t1.a from t1 left join t2 on t2.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
set optimizer_switch='table_elimination=default';
explain select t1.a from t1 left join t2 on t2.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
drop table t1, t2;