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* Which Join is better
@ 2011-08-02 06:42 Adarsh Sharma <adarsh.sharma@orkash.com>
0 siblings, 3 replies; 4+ messages in thread
From: Adarsh Sharma @ 2011-08-02 06:42 UTC (permalink / raw)
To: pgsql-performance
Dear all,
Just want to know which join is better for querying data faster.
I have 2 tables A ( 70 GB ) & B ( 7 MB )
A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
select p.* from table A p, B q where p.id=q.id
or
select p.* from table B q , A p where q.id=p.id
Thanks
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Which Join is better
@ 2011-08-02 06:47 Maria Arias de Reyna <marias@emergya.es>
parent: Adarsh Sharma <adarsh.sharma@orkash.com>
2 siblings, 0 replies; 4+ messages in thread
From: Maria Arias de Reyna @ 2011-08-02 06:47 UTC (permalink / raw)
To: pgsql-performance
El Martes 02 Agosto 2011, Adarsh Sharma escribió:
> Dear all,
>
> Just want to know which join is better for querying data faster.
>
> I have 2 tables A ( 70 GB ) & B ( 7 MB )
>
> A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
>
> select p.* from table A p, B q where p.id=q.id
>
> or
>
> select p.* from table B q , A p where q.id=p.id
>
>
> Thanks
Hi Adarsh,
What does a "EXPLAIN ANALYZE" say after a VACCUM?
--
María Arias de Reyna Domínguez
Área de Operaciones
Emergya Consultoría
Tfno: +34 954 51 75 77 / +34 607 43 74 27
Fax: +34 954 51 64 73
www.emergya.es
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Which Join is better
@ 2011-08-02 06:47 Szymon Guz <mabewlun@gmail.com>
parent: Adarsh Sharma <adarsh.sharma@orkash.com>
2 siblings, 0 replies; 4+ messages in thread
From: Szymon Guz @ 2011-08-02 06:47 UTC (permalink / raw)
To: Adarsh Sharma <adarsh.sharma@orkash.com>; +Cc: pgsql-performance
On 2 August 2011 08:42, Adarsh Sharma <adarsh.sharma@orkash.com> wrote:
> Dear all,
>
> Just want to know which join is better for querying data faster.
>
> I have 2 tables A ( 70 GB ) & B ( 7 MB )
>
> A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
>
> select p.* from table A p, B q where p.id=q.id
>
> or
>
> select p.* from table B q , A p where q.id=p.id
>
>
>
Hi,
it really doesn't matter. PostgreSQL can reorder the joins as it likes.
And you can always check, but I think the plans will be the same.
regards
Szymon
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Which Join is better
@ 2011-08-03 00:16 lars hofhansl <lhofhansl@yahoo.com>
parent: Adarsh Sharma <adarsh.sharma@orkash.com>
2 siblings, 0 replies; 4+ messages in thread
From: lars hofhansl @ 2011-08-03 00:16 UTC (permalink / raw)
To: Adarsh Sharma <adarsh.sharma@orkash.com>; pgsql-performance
Unless you use the explicit join syntax:
select p.* from A p join B q on (p.id = q.id)
and also set join_collapse_limit= 1
The order of the joins is determined by the planner.
Also explain is your friend :)
________________________________
From: Adarsh Sharma <adarsh.sharma@orkash.com>
To: pgsql-performance@postgresql.org
Sent: Monday, August 1, 2011 11:42 PM
Subject: [PERFORM] Which Join is better
Dear all,
Just want to know which join is better for querying data faster.
I have 2 tables A ( 70 GB ) & B ( 7 MB )
A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
select p.* from table A p, B q where p.id=q.id
or
select p.* from table B q , A p where q.id=p.id
Thanks
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^ permalink raw reply [nested|flat] 4+ messages in thread
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2011-08-02 06:42 Which Join is better Adarsh Sharma <adarsh.sharma@orkash.com>
2011-08-02 06:47 ` Maria Arias de Reyna <marias@emergya.es>
2011-08-02 06:47 ` Szymon Guz <mabewlun@gmail.com>
2011-08-03 00:16 ` lars hofhansl <lhofhansl@yahoo.com>
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