(8.0.26)
drop table tab1;
create table tab1(
col1 bigint
,col2 bigint
);
drop table tab2;
create table tab2(
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() * 1000)+1
);
insert into tab2 values(
i
,floor(rand() * 1000)+1
);
end while;
commit;
end
//
delimiter ;
call proc1(1000000);
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);
analyze table tab1;
analyze table tab2;
explain
select /*+ JOIN_PREFIX(t2) NO_INDEX(t2 ind22) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
show warnings;
explain
select /*+ JOIN_PREFIX(t2) */ /*+ NO_INDEX(t2 ind22) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
show warnings;
explain
select /*+ NO_INDEX(t2 ind22) */ /*+ JOIN_PREFIX(t2) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
show warnings;
ヒント句の分割指定は無効で、複数指定した場合、最初のヒント句が使用される
ヒントコメントには複数のヒントを含めることができますが、クエリーブロックに複数のヒントコメントを含めることはできません。
(19c)
drop table tab1 purge;
create table tab1(
col1 int
,col2 int
);
drop table tab2 purge;
create table tab2(
col1 int
,col2 int
);
declare
begin
for i in 1..1000000 loop
insert into tab1 values(
i
,floor(dbms_random.value(1, 1001) )
);
insert into tab2 values(
i
,floor(dbms_random.value(1, 1001) )
);
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);
set time on
set timing on
exec dbms_stats.gather_table_stats(user,'TAB1');
exec dbms_stats.gather_table_stats(user,'TAB2');
explain plan for
select /*+ LEADING(t1 t2) INDEX(t2 tab2pk) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
select * from table(dbms_xplan.display(format=>'ALL') );
explain plan for
select /*+ LEADING(t1 t2) */ /*+ INDEX(t2 tab2pk) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
select * from table(dbms_xplan.display(format=>'ALL') );
explain plan for
select /*+ INDEX(t2 tab2pk) */ /*+ LEADING(t1 t2) */
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
select * from table(dbms_xplan.display(format=>'ALL') );
ヒント句の分割指定は無効で、複数指定した場合、最初のヒント句が使用される
ヒントの使用方法
文ブロックはヒントを含むコメントを1つだけ持つことができ、
SELECT、UPDATE、INSERT、MERGEまたはDELETEの各キーワードに続けてコメントを指定します。
(14)
drop table tab1;
create table tab1(
col1 bigint
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint
,col2 bigint
);
start transaction;
insert into tab1 select
g
,floor(random() * 1000)+1
from generate_series(1,1000000) g;
commit;
start transaction;
insert into tab2 select
g
,floor(random() * 1000)+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);
\timing 1
\pset pager 0
analyze tab1;
analyze tab2;
set pg_hint_plan.debug_print=1;
show pg_hint_plan.debug_print;
/*+ Leading( (t2 t1) ) NestLoop(t1 t2) */
explain
select
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
/*+ Leading( (t2 t1) ) */ /*+ NestLoop(t1 t2) */
explain
select
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
/*+ NestLoop(t1 t2) */ /*+ Leading( (t2 t1) ) */
explain
select
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where mod(t2.col1,3) = 0
;
ヒント句の分割指定は無効で、複数指定した場合、最初のヒント句が使用される
pg_hint_plan reads hints from only the first block comment
(2019)
drop table tab1;
create table tab1(
col1 bigint not null
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint not null
,col2 bigint
);
set nocount on
declare @i int;
set @i = 1;
begin transaction;
while @i <= 1000000
begin
insert into tab1 values(
@i
,floor(rand() * 1000)+1
);
insert into tab2 values(
@i
,floor(rand() * 1000)+1
);
set @i = @i + 1;
end
commit;
select count(*) from tab1;
select top 20 * from tab1 order by newid();
alter table tab1 add constraint tab1pk primary key (col1);
create index ind12 on tab1(col2);
select count(*) from tab2;
select top 20 * from tab2 order by newid();
alter table tab2 add constraint tab2pk primary key (col1);
create index ind22 on tab2(col2);
set statistics time on
update statistics tab1;
update statistics tab2;
select
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where t2.col1%3 = 0
OPTION(LOOP JOIN , TABLE HINT(t1, FORCESEEK) );
select
count(1)
from tab1 t1
inner join tab2 t2
on t1.col2 = t2.col2
where t2.col1%3 = 0
OPTION(LOOP JOIN)
OPTION(TABLE HINT(t1, FORCESEEK) );
;
ヒント句の分割指定は無効で、複数指定した場合、構文エラーとなる
