Re: Query take 101 minutes, help, please - Mailing list pgsql-performance
| From | Meetesh Karia |
|---|---|
| Subject | Re: Query take 101 minutes, help, please |
| Date | |
| Msg-id | fc5b04ca0509071009388d72f1@mail.gmail.com Whole thread Raw |
| In response to | Query take 101 minutes, help, please (Christian Compagnon <ccompagnon@gmail.com>) |
| Responses |
Re: Query take 101 minutes, help, please
(Alex Hayward <xelah-pgsql@xelah.com>)
|
| List | pgsql-performance |
PG is creating the union of January, February and March tables first and that doesn't have an index on it. If you're going to do many queries using the union of those three tables, you might want to place their contents into one table and create an index on it.
Otherwise, try something like this:
SELECT "Rut Cliente"
FROM "Internet_Abril"
WHERE "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Enero")
AND "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Febrero")
AND "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Marzo");
You could also compare the performance of that to this and choose the one that works the best:
SELECT "Rut Cliente"
FROM "Internet_Abril" a
LEFT JOIN "Internet_Enero" e ON a."Rut Cliente" = e."Rut Cliente"
LEFT JOIN "Internet_Febrero" f ON a."Rut Cliente" = f."Rut Cliente"
LEFT JOIN "Internet_Marzo" m ON a."Rut Cliente" = m."Rut Cliente"
WHERE e."Rut Cliente" IS NULL AND f."Rut Cliente" IS NULL and m."Rut Cliente" IS NULL;
Meetesh
Otherwise, try something like this:
SELECT "Rut Cliente"
FROM "Internet_Abril"
WHERE "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Enero")
AND "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Febrero")
AND "Rut Cliente" NOT IN (SELECT "Rut Cliente" FROM
"Internet_Marzo");
You could also compare the performance of that to this and choose the one that works the best:
SELECT "Rut Cliente"
FROM "Internet_Abril" a
LEFT JOIN "Internet_Enero" e ON a."Rut Cliente" = e."Rut Cliente"
LEFT JOIN "Internet_Febrero" f ON a."Rut Cliente" = f."Rut Cliente"
LEFT JOIN "Internet_Marzo" m ON a."Rut Cliente" = m."Rut Cliente"
WHERE e."Rut Cliente" IS NULL AND f."Rut Cliente" IS NULL and m."Rut Cliente" IS NULL;
Meetesh
On 9/7/05, Christian Compagnon <ccompagnon@gmail.com> wrote:
Hello,
I'm a newbie in postgresql, I've installed it on a Windows XP machine
( I can't use linux, it's a company machine ), I'm courious why this
query takes so long
SELECT "Rut Cliente"
FROM "Internet_Abril"
WHERE "Rut Cliente" NOT IN ((SELECT "Rut Cliente" FROM
"Internet_Enero") UNION (SELECT "Rut Cliente" FROM
"Internet_Febrero") UNION (SELECT "Rut Cliente" FROM
"Internet_Marzo"));
it takes about 100 minutes to complete the query.
All tables has index created ( Rut Cliente is a VarChar ), and tables
has 50.000 records each.
The explain for the query tells the following
"QUERY PLAN
Seq Scan on "Internet_Abril" (cost=19406.67..62126112.70 rows=24731 width=13)
Filter: (NOT (subplan))
SubPlan
-> Materialize (cost=19406.67..21576.07 rows=136740 width=13)
-> Unique (cost=17784.23..18467.93 rows=136740 width=13)
-> Sort (cost=17784.23..18126.08 rows=136740 width=13)
Sort
Key: "Rut Cliente"
-> Append (cost=0.00..3741.80 rows=136740 width=13)
-> Subquery Scan "*SELECT* 1" (cost=0.00..1233.38
rows=45069 width=13)
-> Seq Scan on "Internet_Enero" (cost=0.00..782.69
rows=45069 width=13)
-> Subquery Scan "*SELECT* 2" (cost=0.00..1104.06
rows=40353 width=13)
-> Seq Scan on "Internet_Febrero" (cost=0.00..700.53
rows=40353 width=13)
-> Subquery Scan "*SELECT* 3" (cost=0.00..1404.36
rows=51318 width=13)
-> Seq Scan on "Internet_Marzo" (cost=0.00..891.18
rows=51318 width=13)
Any help will be apreciated, It's for my thesis
saludos
Christian
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