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--disable_warnings
drop table if exists t0, t1, t2, t3, t4;
--enable_warnings
#
# 1. Subquery with GROUP/HAVING
#
create table t1 (oref int, grp int, ie int) ;
insert into t1 (oref, grp, ie) values
(1, 1, 1),
(1, 1, 1),
(1, 2, NULL),
(2, 1, 3),
(3, 1, 4),
(3, 2, NULL);
# Ok, for
# select max(ie) from t1 where oref=PARAM group by grp
# we'll have:
# 1 -> (1, NULL) matching + NULL
# 2 -> (3) non-matching
# 3 -> (3, NULL) non-matching + NULL
# 4 -> () nothing.
create table t2 (oref int, a int);
insert into t2 values
(1, 1),
(2, 2),
(3, 3),
(4, NULL),
(2, NULL);
# true, false, null, false, null
select a, oref, a in (select max(ie)
from t1 where oref=t2.oref group by grp) from t2;
# This must have a trigcond
explain extended
select a, oref, a in (select max(ie)
from t1 where oref=t2.oref group by grp) from t2;
# This must not have a trigcond:
explain extended
select a, oref from t2
where a in (select max(ie) from t1 where oref=t2.oref group by grp);
# Non-correlated subquery, 2 NULL evaluations
create table t3 (a int);
insert into t3 values (NULL), (NULL);
flush status;
select a in (select max(ie) from t1 where oref=4 group by grp) from t3;
show status like 'Handler_read_rnd_next';
select ' ^ This must show 11' Z;
# This must show trigcond:
explain extended select a in (select max(ie) from t1 where oref=4 group by grp) from t3;
drop table t1, t2, t3;
#
# 2. Subquery handled with 'index_subquery':
#
create table t1 (a int, oref int, key(a));
insert into t1 values
(1, 1),
(1, NULL),
(2, 3),
(2, NULL),
(3, NULL);
create table t2 (a int, oref int);
insert into t2 values (1, 1), (2,2), (NULL, 3), (NULL, 4);
select oref, a, a in (select a from t1 where oref=t2.oref) Z from t2;
# The next explain shows "using index" but that is just incorrect display
# (there is a bug filed about this).
explain extended
select oref, a, a in (select a from t1 where oref=t2.oref) Z from t2;
flush status;
select oref, a from t2 where a in (select a from t1 where oref=t2.oref);
# This will only show access to t2:
show status like '%Handler_read_rnd_next';
# Check that repeated NULL-scans are not cached (subq. is not correlated):
delete from t2;
insert into t2 values (NULL, 0),(NULL, 0), (NULL, 0), (NULL, 0);
flush status;
select oref, a, a in (select a from t1 where oref=t2.oref) Z from t2;
show status like '%Handler_read%';
select 'No key lookups, seq reads: 29= 5 reads from t2 + 4 * 6 reads from t1.' Z;
drop table t1, t2;
#
# 3. Subquery handled with 'unique_index_subquery':
#
create table t1 (a int, b int, primary key (a));
insert into t1 values (1,1), (3,1),(100,1);
create table t2 (a int, b int);
insert into t2 values (1,1),(2,1),(NULL,1),(NULL,0);
select a,b, a in (select a from t1 where t1.b = t2.b) Z from t2 ;
drop table t1, t2;
#
# 4. Subquery that is a join, with ref access
#
create table t1 (a int, b int, key(a));
insert into t1 values
(0,0),(1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7),(8,8),(9,9);
create table t2 like t1;
insert into t2 select * from t1;
update t2 set b=1;
create table t3 (a int, oref int);
insert into t3 values (1, 1), (NULL,1), (NULL,0);
select a, oref,
t3.a in (select t1.a from t1, t2 where t1.b=t2.a and t2.b=t3.oref) Z
from t3;
# This must have trigcond in WHERE and HAVING:
explain extended
select a, oref,
t3.a in (select t1.a from t1, t2 where t1.b=t2.a and t2.b=t3.oref) Z
from t3;
drop table t1, t2, t3;
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