database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-08-07 00:04:31 +03:00
Code Activity
Files
MDEV-36812
mariadb/mysql-test/suite/vcol/r/vcol_select_innodb.result
Yuchen Pei 8cdee25952 MDEV-36132 Substitute vcol expressions with indexed vcol fields in ORDER BY and GROUP BY 
Also expand vcol field index coverings to include indexes covering all
the fields in the expression. The reasoning goes as follows: let f(c1,
c2, ..., cn) be a function on applied to columns c1, c2, ..., cn, if
f(...) is covered by an index, so should vc whose expression is
f(...).

For example, if t.vf = t.c1 + t.c2, and t has three indexes (vf), (c1,
c2), (c1).

Before this change, vf's index covering is a singleton {(vf)}. Let's call
that the "conventional" index covering.

After this change vf's index covering is now {(vf), (c1, c2)}, since
(c1, c2) covers both c1 and c2. Let's call (c1, c2) in this case the
"extra" covering.

With the coverings updated, when an index in the "extra" covering is
chosen for keyread, the vcol also needs to be calculated. In this case
we mark vcol in the table read_set, and ensure it is computed.

With these changes, we see various improvements, including from using
full table scan + filesort to full index scan + filesort when ORDER BY
an indexed vcol (here vc = c + 1 is a vcol and both c and vc are
indexes):

 explain select c + 1 from t order by vc;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	10000	Using filesort
+1	SIMPLE	t	index	NULL	c	5	NULL	10000	Using index; Using filesort

The substitutions are followed updates to all_fields which include a
copy of the ORDER BY/GROUP BY item pointers, as well as corresponding
updates to ref_pointer_array so that the all_fields and
ref_pointer_array remain in sync.

Another, related change is the recomputation of table index covering
on substitutions. It not only reflects the correct table index
covering after the substitutions, but also improve executions where
the vcol index can be chosen, such as this example (here vc = c + 1
and vc is the only index in the table), from full table scan +
filesort to full index scan:

select vc from t order by c + 1;

We do it in SELECT as well as in single table DELETE/UPDATE.
2025-07-22 10:44:12 +10:00

271 lines
9.2 KiB
Plaintext
Raw Permalink Blame History

SET @@session.default_storage_engine = 'InnoDB';
SET @save_stats_persistent=@@GLOBAL.innodb_stats_persistent;
SET GLOBAL innodb_stats_persistent=0;
create table t1 (a int,
b int as (-a),
c int as (-a) persistent,
index (c));
insert into t1 (a) values (2), (1), (1), (3), (NULL);
create table t2 like t1;
insert into t2 (a) values (1);
create table t3 (a int primary key,
b int as (-a),
c int as (-a) persistent unique);
insert into t3 (a) values (2),(1),(3),(5),(4),(7);
# select_type=SIMPLE, type=system
select * from t2;
a b c
1 -1 -1
explain select * from t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 1
select * from t2 where c=-1;
a b c
1 -1 -1
explain select * from t2 where c=-1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ref c c 5 const 1
# select_type=SIMPLE, type=ALL
select * from t1 where b=-1;
a b c
1 -1 -1
1 -1 -1
explain select * from t1 where b=-1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 Using where
# select_type=SIMPLE, type=const
select * from t3 where a=1;
a b c
1 -1 -1
explain select * from t3 where a=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 const PRIMARY PRIMARY 4 const 1
# select_type=SIMPLE, type=range
select * from t3 where c>=-1;
a b c
1 -1 -1
explain select * from t3 where c>=-1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range c c 5 NULL 1 Using where; Using index
# select_type=SIMPLE, type=ref
select * from t1,t3 where t1.c=t3.c and t3.c=-1;
a b c a b c
1 -1 -1 1 -1 -1
1 -1 -1 1 -1 -1
explain select * from t1,t3 where t1.c=t3.c and t3.c=-1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 const c c 5 const 1 Using index
1 SIMPLE t1 ref c c 5 const 2
# select_type=PRIMARY, type=index,ALL
select * from t1 where b in (select c from t3);
a b c
2 -2 -2
1 -1 -1
1 -1 -1
3 -3 -3
explain select * from t1 where b in (select c from t3);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 5 Using where
1 PRIMARY t3 eq_ref c c 5 test.t1.b 1 Using index
# select_type=PRIMARY, type=range,ref
select * from t1 where c in (select c from t3 where c between -2 and -1);
a b c
2 -2 -2
1 -1 -1
1 -1 -1
explain select * from t1 where c in (select c from t3 where c between -2 and -1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t3 range c c 5 NULL 2 Using where; Using index
1 PRIMARY t1 ref c c 5 test.t3.c 1
# select_type=UNION, type=system
# select_type=UNION RESULT, type=<union1,2>
select * from t1 union select * from t2;
a b c
2 -2 -2
1 -1 -1
3 -3 -3
NULL NULL NULL
explain select * from t1 union select * from t2;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 5
2 UNION t2 ALL NULL NULL NULL NULL 1
NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL
# select_type=DERIVED, type=system
set @tmp_optimizer_switch=@@optimizer_switch;
set optimizer_switch='derived_merge=off,derived_with_keys=off';
select * from (select a,b,c from t1) as t11;
a b c
2 -2 -2
1 -1 -1
1 -1 -1
3 -3 -3
NULL NULL NULL
explain select * from (select a,b,c from t1) as t11;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 5
2 DERIVED t1 ALL NULL NULL NULL NULL 5
set optimizer_switch=@tmp_optimizer_switch;
###
### Using aggregate functions with/without DISTINCT
###
# SELECT COUNT(*) FROM tbl_name
select count(*) from t1;
count(*)
5
explain select count(*) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL c 5 NULL 5 Using index
# SELECT COUNT(DISTINCT <non-vcol>) FROM tbl_name
select count(distinct a) from t1;
count(distinct a)
3
explain select count(distinct a) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5
# SELECT COUNT(DISTINCT <non-stored vcol>) FROM tbl_name
select count(distinct b) from t1;
count(distinct b)
3
explain select count(distinct b) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5
# SELECT COUNT(DISTINCT <stored vcol>) FROM tbl_name
select count(distinct c) from t1;
count(distinct c)
3
explain select count(distinct c) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL c 5 NULL 5 Using index for group-by
###
### filesort & range-based utils
###
# SELECT * FROM tbl_name WHERE <vcol expr>
select * from t3 where c >= -2;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where c >= -2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range c c 5 NULL 2 Using where; Using index
# SELECT * FROM tbl_name WHERE <non-vcol expr>
select * from t3 where a between 1 and 2;
a b c
1 -1 -1
2 -2 -2
explain select * from t3 where a between 1 and 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range PRIMARY PRIMARY 4 NULL 2 Using where
# SELECT * FROM tbl_name WHERE <non-indexed vcol expr>
select * from t3 where b between -2 and -1;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where b between -2 and -1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index NULL c 5 NULL 6 Using where; Using index
# SELECT * FROM tbl_name WHERE <indexed vcol expr>
select * from t3 where c between -2 and -1;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where c between -2 and -1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range c c 5 NULL 2 Using where; Using index
# SELECT * FROM tbl_name WHERE <non-vcol expr> ORDER BY <non-indexed vcol>
select * from t3 where a between 1 and 2 order by b;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where a between 1 and 2 order by b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range PRIMARY PRIMARY 4 NULL 2 Using where; Using filesort
# SELECT * FROM tbl_name WHERE <non-vcol expr> ORDER BY <indexed vcol>
select * from t3 where a between 1 and 2 order by c;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where a between 1 and 2 order by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index PRIMARY c 5 NULL 6 Using where; Using index
# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <non-vcol>
select * from t3 where b between -2 and -1 order by a;
a b c
1 -1 -1
2 -2 -2
explain select * from t3 where b between -2 and -1 order by a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index NULL PRIMARY 4 NULL 6 Using where
# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <non-indexed vcol>
select * from t3 where b between -2 and -1 order by b;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where b between -2 and -1 order by b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index NULL c 5 NULL 6 Using where; Using index; Using filesort
# SELECT * FROM tbl_name WHERE <indexed vcol expr> ORDER BY <non-indexed vcol>
select * from t3 where c between -2 and -1 order by b;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where c between -2 and -1 order by b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range c c 5 NULL 2 Using where; Using index; Using filesort
# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <indexed vcol>
select * from t3 where b between -2 and -1 order by c;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where b between -2 and -1 order by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index NULL c 5 NULL 6 Using where; Using index
# SELECT * FROM tbl_name WHERE <indexed vcol expr> ORDER BY <indexed vcol>
select * from t3 where c between -2 and -1 order by c;
a b c
2 -2 -2
1 -1 -1
explain select * from t3 where c between -2 and -1 order by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 range c c 5 NULL 2 Using where; Using index
# SELECT sum(<non-indexed vcol>) FROM tbl_name GROUP BY <non-indexed vcol>
select sum(b) from t1 group by b;
sum(b)
NULL
-3
-2
-2
explain select sum(b) from t1 group by b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 Using temporary; Using filesort
# SELECT sum(<indexed vcol>) FROM tbl_name GROUP BY <indexed vcol>
select sum(c) from t1 group by c;
sum(c)
NULL
-3
-2
-2
explain select sum(c) from t1 group by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL c 5 NULL 5 Using index
# SELECT sum(<non-indexed vcol>) FROM tbl_name GROUP BY <indexed vcol>
select sum(b) from t1 group by c;
sum(b)
NULL
-3
-2
-2
explain select sum(b) from t1 group by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL c 5 NULL 5
# SELECT sum(<indexed vcol>) FROM tbl_name GROUP BY <non-indexed vcol>
select sum(c) from t1 group by b;
sum(c)
NULL
-3
-2
-2
explain select sum(c) from t1 group by b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 Using temporary; Using filesort
SET GLOBAL innodb_stats_persistent=@save_stats_persistent;
View Git Blame Copy Permalink