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create table t1(c1 integer not null,c2 integer not null, key (c1)) engine=InnoDb;
create view v1 as select * from t1 where c1 in (0,1);
insert t1 select 0,seq from seq_1_to_500;
insert t1 select 1,seq from seq_1_to_100;
insert t1 select 2,seq from seq_1_to_50;
insert t1 select 3,seq from seq_1_to_20;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
#
# Delete with limit (quick select - range acces)
#
start transaction;
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) = 500 limit 1;
affected rows: 1
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) = 500 limit 1;
affected rows: 0
select count(*) from v1 where c1=0;
count(*)
499
rollback;
#
# Delete
#
start transaction;
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) = 500 ;
affected rows: 500
rollback;
#
# Delete with exists
#
start transaction;
select count(*) from v1 where c1=2;
count(*)
0
delete from t1 where c1=2 and exists(select 'x' from t1 b where b.c2<10);
affected rows: 50
delete from t1 where c1=2 and exists(select 'x' from t1 b where b.c2<10);
affected rows: 0
select count(*) from v1 where c1=2;
count(*)
0
rollback;
#
# Delete through a view with limit (range access)
#
start transaction;
explain delete from v1 where (select count(*) from t1 b where b.c1=v1.c1) = 500 limit 1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 range c1 c1 4 NULL 600 Using where
2 DEPENDENT SUBQUERY b ref c1 c1 4 test.t1.c1 167 Using index
delete from v1 where (select count(*) from t1 b where b.c1=v1.c1) = 500 limit 1;
affected rows: 1
delete from v1 where (select count(*) from t1 b where b.c1=v1.c1) = 500 limit 1;
affected rows: 0
select count(*) from v1 where c1=0;
count(*)
499
rollback;
#
# Delete through a view (ALL access)
#
start transaction;
explain delete from v1 where (select count(*) from t1 b where b.c1=v1.c1) = 500;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL c1 NULL NULL NULL 670 Using where
2 DEPENDENT SUBQUERY b ref c1 c1 4 test.t1.c1 167 Using index
delete from v1 where (select count(*) from t1 b where b.c1=v1.c1) = 500 ;
affected rows: 500
select count(*) from v1 where c1=0;
count(*)
0
rollback;
#
# Delete failed due to trigger
#
create trigger trg after delete on t1 for each row
begin
declare c int;
begin
if old.c1 = 1 then
select count(*) into c from t1 where c1!=old.c1;
SIGNAL SQLSTATE '45000' set table_name=c;
end if;
end;
end;
/
start transaction;
delete from t1 where c1=1 and (select count(*) from t1 b where b.c1=t1.c1) > 0 order by c2 asc limit 10;
ERROR 45000: Unhandled user-defined exception condition
rollback;
start transaction;
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) > 0 order by c1 desc limit 100;
ERROR 45000: Unhandled user-defined exception condition
select c1,count(*) from t1 group by c1;
c1 count(*)
0 500
1 100
2 50
3 20
rollback;
drop trigger trg;
#
# Delete through a view with returning
#
start transaction;
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) = 500 order by c2 asc limit 10 returning c1,c2;
c1 c2
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
0 10
rollback;
start transaction;
delete from t1 where (select count(*) from t1 b where b.c1=t1.c1) = 500 order by c2 desc limit 10 returning c1,c2;
c1 c2
0 491
0 492
0 493
0 494
0 495
0 496
0 497
0 498
0 499
0 500
rollback;
drop view v1;
drop table t1;
#
# Delete from table with more than 150000 rows
#
create table t1(c1 integer not null,c2 integer not null, key (c1));
insert t1 select 0,seq from seq_1_to_128000;
insert t1 select 1,seq from seq_1_to_25600;
select count(*) from t1;
count(*)
153600
# with a lot of memory for sort_buffer_size
set session sort_buffer_size = 1024000;
delete from t1 where c1=0 and exists(select 'x' from t1 b where b.c1<10);
affected rows: 128000
# with little memory for sort_buffer_size
insert t1 select 0,seq from seq_1_to_128000;
set session sort_buffer_size = 1024;
delete from t1 where c1=0 and exists(select 'x' from t1 b where b.c1<10);
affected rows: 128000
drop table t1;
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