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drop table if exists t0;
create table t0 (a int) engine=myisam;
insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
#
# Tests for single-table DELETE
#
explain select * from t0 where a=3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 ALL NULL NULL NULL NULL 8 Using where
explain delete from t0 where a=3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 ALL NULL NULL NULL NULL 8 Using where
# DELETE without WHERE is a special case:
explain delete from t0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Deleting all rows
create table t1 (a int, b int, filler char(100), key(a), key(b));
insert into t1
select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler'
from t0 A, t0 B, t0 C;
# This should use an index, possible_keys=NULL because there is no WHERE
explain delete from t1 order by a limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL a NULL NULL 512
# This should use range, possible_keys={a,b}
explain delete from t1 where a<20 and b < 10;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a,b a 5 NULL 1 Using where
# This should use ALL + filesort
explain delete from t1 order by a+1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 512 Using filesort
# This should use range + using filesort
explain delete from t1 where a<20 order by b limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a a 5 NULL 1 Using where; Using filesort
# Try some subqueries:
explain delete from t1 where a < (select max(a) from t0);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 range a a 5 NULL 1 Using where
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Query plan already deleted
explain delete from t1 where a < (select max(a) from t0 where a < t1.b);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 512 Using where
2 DEPENDENT SUBQUERY t0 ALL NULL NULL NULL NULL 8 Using where
#
# Tests for multi-table DELETE
#
explain delete t1 from t0, t1 where t0.a = t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 ALL NULL NULL NULL NULL 8 Using where
1 SIMPLE t1 ref a a 5 test.t0.a 4 Using index
drop table t0, t1;
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