ビューとアクセスヒント句

• MySQL

(8.0.26)

drop table tab1;
create table tab1(
    col1 bigint 
   ,col2 bigint
   );

drop table tab2;
create table tab2(
    col1 bigint 
   ,col2 bigint
   );

drop table tab3;
create table tab3(
    col1 bigint 
   ,col2 bigint
   );

drop procedure proc1;

delimiter //
create procedure proc1(in x int)
begin
  declare i int;
  set i = 0;
  start transaction;
  while i < x do
    set i = i + 1;
    insert into tab1 values(
     i
    ,floor(rand() * 10000)+1
    );
    insert into tab2 values(
     i
    ,floor(rand() * 10000)+1
    );
    insert into tab3 values(
     i
    ,floor(rand() * 10000)+1
    );
  end while;
  commit;
end
//
delimiter ;

call proc1(100000);

select count(*) from tab1;
select * from tab1 order by rand() limit 20;
alter table tab1 add constraint tab1pk primary key (col1);
create index ind12 on tab1(col2);

select count(*) from tab2;
select * from tab2 order by rand() limit 20;
alter table tab2 add constraint tab2pk primary key (col1);
create index ind22 on tab2(col2);

select count(*) from tab3;
select * from tab3 order by rand() limit 20;
alter table tab3 add constraint tab3pk primary key (col1);
create index ind32 on tab3(col2);

analyze table tab1;
analyze table tab2;
analyze table tab3;

create or replace view view11 as
select  t21.col2 from tab2 t21 inner join tab3 t22
on t21.col1 = t22.col1
where t21.col2 < 5000
group by t21.col2
having count(t22.col2) > 100
;

create or replace view view21 as
select  t31.col2 from tab2 t31 inner join tab3 t32
on t31.col1 = t32.col1
;

--2. 動作確認
explain analyze
select  /*+ NO_INDEX(t31 ind22) */    count(*) from tab1 t1
inner join view11 t2
on t1.col2 = t2.col2
inner join view21  t3
on t1.col2 = t3.col2
;
show warnings;

-- ビュー内部名を本体に指定

/*+ NO_INDEX(t21 ind22) */    → Unresolved
/*+ NO_INDEX(t31 ind22) */    → Unresolved

• Oracle

(19c)

https://ameblo.jp/keshi0414/entry-12318306543.html
https://qiita.com/mkyz08/items/9dfa4a5ea636238afc3e
https://blogs.oracle.com/otnjp/post/tsushima-hakushi-55

-- 1. テストデータ作成

drop table tab1 purge;
create table tab1(
    col1 int 
   ,col2 int
  );

drop table tab2 purge;
create table tab2(
    col1 int 
   ,col2 int
   );

drop table tab3 purge;
create table tab3(
    col1 int 
   ,col2 int
   );

declare
begin
for i in 1..1000000 loop
  insert into tab1 values(
    i
   ,floor(dbms_random.value(1, 10001) )
   );
  
  insert into tab2 values(
    i
   ,floor(dbms_random.value(1, 10001) )
   );
  insert into tab3 values(
    i
   ,floor(dbms_random.value(1, 10001) )
   );
end loop;
end;
/

commit;

select count(*) from tab1;
select * from tab1 order by dbms_random.value()  fetch first 20 rows only;
alter table tab1 add constraint tab1pk primary key (col1);
create index ind12 on tab1(col2);

select count(*) from tab2;
select * from tab2 order by dbms_random.value()  fetch first 20 rows only;
alter table tab2 add constraint tab2pk primary key (col1);
create index ind22 on tab2(col2);

select count(*) from tab3;
select * from tab3 order by dbms_random.value()  fetch first 20 rows only;
alter table tab3 add constraint tab3pk primary key (col1);
create index ind32 on tab3(col2);

set time on
set timing on

exec dbms_stats.gather_table_stats(user,'TAB1');
exec dbms_stats.gather_table_stats(user,'TAB2');
exec dbms_stats.gather_table_stats(user,'TAB3');

create or replace view view1 as
select  t21.col2 from tab2 t21 inner join tab3 t22
on t21.col1 = t22.col1
where t21.col2 < 5000
group by t21.col2
having count(t22.col2) > 100
;

create or replace view view2 as
select  t21.col2 from tab2 t21 , tab3 t22
where t21.col1 = t22.col1
and t21.col2 < 5000
group by t21.col2
having count(t22.col2) > 100
;

create or replace view view21 as
select  t31.col2 from tab2 t31 inner join tab3 t32
on t31.col1 = t32.col1
;

create or replace view view22 as
select  t31.col2 from tab2 t31 , tab3 t32
where t31.col1 = t32.col1
;

--2. 動作確認

[1]ANSI準拠の結合文

explain plan for
select /*+ INDEX_FFS(t3.t32 tab3pk)  */     count(*) from tab1 t1
inner join
view11 t2
on t1.col2 = t2.col2
inner join
view21 t3
on t1.col2 = t3.col2
;

select * from table(dbms_xplan.display(format=>'ALL') );

--1.1 問合せブロック付きヒント(システム生成)

/*+ INDEX_FFS(T32@SEL$5 tab3pk) */  →OK
/*+ INDEX(t21@SEL$2  ind22) */  → Unresolved

グループ化したビュー内のテーブルに対しては、本体クエリでアクセスパスヒント句指定不可

--1.2 グローバル・ヒント
/*+ INDEX_FFS(t3.t32 tab3pk)  */  →グローバルヒントが認識されない ★

--1.3 ビュー内部名を本体に指定
/*+ INDEX_FFS(t32 tab3pk)  */  → Unresolved

[2]Oracle固有の結合文

explain plan for
select /*+ INDEX_FFS(t3.t32 tab3pk)  */     count(*) from tab1 t1
,view12 t2
,view22 t3
where t1.col2 = t2.col2
and t1.col2 = t3.col2
;

select * from table(dbms_xplan.display(format=>'ALL') );

--2.1 問合せブロック付きヒント(システム生成)

/*+ INDEX_FFS(T32@SEL$3 tab3pk) */  →OK
/*+ INDEX(t21@SEL$2  ind22) */  → Unresolved

グループ化したビュー内のテーブルに対しては、本体クエリでアクセスパスヒント句指定不可

--2.2 グローバル・ヒント
/*+ INDEX_FFS(t3.t32 tab3pk)  */  →OK

--2.3 ビュー内部名を本体に指定
/*+ INDEX_FFS(t32 tab3pk)  */  → Unresolved

• PostgreSQL

(14)

-- 1. テストデータ作成

drop table tab1;
create table tab1(
    col1 bigint 
   ,col2 bigint
  );
drop table tab2;
create table tab2(
    col1 bigint 
   ,col2 bigint
   );
   
drop table tab3;
create table tab3(
    col1 bigint 
   ,col2 bigint
   );

start transaction;
insert into tab1 select
   g
  ,floor(random() * 10000)+1
from generate_series(1,1000000) g;

commit;

start transaction;
insert into tab2 select
   g
  ,floor(random() * 10000)+1
from generate_series(1,1000000) g;

commit;

start transaction;
insert into tab3 select
   g
  ,floor(random() * 10000)+1
from generate_series(1,1000000) g;

commit;

select count(*) from tab1;
select * from tab1 order by random() limit 20;
alter table tab1 add constraint tab1pk primary key (col1);
create index ind12 on tab1(col2);
select count(*) from tab2;
select * from tab2 order by random() limit 20;
alter table tab2 add constraint tab2pk primary key (col1);
create index ind22 on tab2(col2);
select count(*) from tab3;
select * from tab3 order by random() limit 20;
alter table tab3 add constraint tab3pk primary key (col1);
create index ind32 on tab3(col2);

\timing 1
\pset pager 0
set pg_hint_plan.debug_print = on;

analyze tab1;
analyze tab2;
analyze tab3;

create or replace view view11 as
select  t21.col2 from tab2 t21 inner join tab3 t22
on t21.col1 = t22.col1
where t21.col2 < 5000
group by t21.col2
having count(t22.col2) > 100
;

create or replace view view21 as
select  t31.col2 from tab2 t31 inner join tab3 t32
on t31.col1 = t32.col1
;

--2. 動作確認

/*+ SeqScan(t21) */ 
explain 
select  count(*) from tab1 t1
inner join
view11 t2
on t1.col2 = t2.col2
inner join
view21 t3
on t1.col2 = t3.col2
;

-- ビュー内部名を本体に指定

/*+ BitmapScan(t31) */  → used hint
/*+ SeqScan(t21) */    → used hint

• SQL Server

(2019)
SQL Serverは調査観点なし