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MWL#17: Table elimination

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- Correctly handle the case where we have multi-table DELETE and a table
  that we're deleting from looks like it could be eliminated.
This commit is contained in:
Sergey Petrunya 2009-08-24 10:12:42 +02:00
commit 21d2573908
3 changed files with 61 additions and 2 deletions
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29
mysql-test/r/table_elim.result
View file

@ -278,3 +278,32 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 10 NULL 2 Using index
1 SIMPLE t2 ref a a 3 test.t1.a 2
drop table t1, t2;
#
# check UPDATE/DELETE that look like they could be eliminated
#
create table t1 (a int primary key, b int);
insert into t1 values (1,1),(2,2),(3,3);
create table t2 like t1;
insert into t2 select * from t1;
update t1 left join t2 using (a) set t2.a=t2.a+100;
select * from t1;
a b
1 1
2 2
3 3
select * from t2;
a b
101 1
102 2
103 3
delete from t2;
insert into t2 select * from t1;
delete t2 from t1 left join t2 using (a);
select * from t1;
a b
1 1
2 2
3 3
select * from t2;
a b
drop table t1, t2;

20
mysql-test/t/table_elim.test
View file

@ -229,3 +229,23 @@ explain select t1.* from t1 left join t2 on t2.a=t1.a;
drop table t1, t2;
--echo #
--echo # check UPDATE/DELETE that look like they could be eliminated
--echo #
create table t1 (a int primary key, b int);
insert into t1 values (1,1),(2,2),(3,3);
create table t2 like t1;
insert into t2 select * from t1;
update t1 left join t2 using (a) set t2.a=t2.a+100;
select * from t1;
select * from t2;
delete from t2;
insert into t2 select * from t1;
delete t2 from t1 left join t2 using (a);
select * from t1;
select * from t2;
drop table t1, t2;