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* using limit @ 2010-12-16 19:18 Anibal David Acosta <aa@devshock.com> 0 siblings, 1 reply; 4+ messages in thread From: Anibal David Acosta @ 2010-12-16 19:18 UTC (permalink / raw) To: pgsql-admin Hi I really like to do efficient SQL queries so, my question is if I am expecting no more than one row from a select, using the LIMIT 1 could improve the performance? If I use my logic, the LIMIT 1 instruction tell to postgres that stop searching when found 1 record, but maybe it is unnecessary Thanks Anibal ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: using limit @ 2010-12-16 19:23 Michael Holt <michael@aers.ca> parent: Anibal David Acosta <aa@devshock.com> 0 siblings, 1 reply; 4+ messages in thread From: Michael Holt @ 2010-12-16 19:23 UTC (permalink / raw) To: Anibal David Acosta <aa@devshock.com>; pgsql-admin This really depends on the type of query you’re talking about. If there’s only one row in the table you’re querying then no, I don’t think it’ll change anything. If you’re querying a single row using a primary key it shouldn’t change anything. If you’re doing an aggregate query, say a sum of a bunch of rows, it also won’t improve performance. If you’re doing a query on a table with multiple rows and not filtering by a primary key or other unique index then yes, it will improve the query. *From:* pgsql-admin-owner@postgresql.org [mailto: pgsql-admin-owner@postgresql.org] *On Behalf Of *Anibal David Acosta *Sent:* Thursday, December 16, 2010 11:19 AM *To:* pgsql-admin@postgresql.org *Subject:* [ADMIN] using limit Hi I really like to do efficient SQL queries so, my question is if I am expecting no more than one row from a select, using the LIMIT 1 could improve the performance? If I use my logic, the LIMIT 1 instruction tell to postgres that stop searching when found 1 record, but maybe it is unnecessary Thanks Anibal ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: using limit @ 2010-12-16 19:33 Anibal David Acosta <aa@devshock.com> parent: Michael Holt <michael@aers.ca> 0 siblings, 1 reply; 4+ messages in thread From: Anibal David Acosta @ 2010-12-16 19:33 UTC (permalink / raw) To: 'Michael Holt' <michael@aers.ca>; pgsql-admin Is a table with 10 million of rows with a primary key but conditions used in select are not part of PK. My table is like this: Column 1 - PK Column 2 - Indexed Column 3 - Indexed Column 2 and Column 3 are Indexed in the same index but they are not mark as unique or PK The Query is like this: Select column1 from myTable where Column2 between X and Y I am expecting just one record De: Michael Holt [mailto:michael@aers.ca] Enviado el: jueves, 16 de diciembre de 2010 04:23 p.m. Para: Anibal David Acosta; pgsql-admin@postgresql.org Asunto: RE: [ADMIN] using limit This really depends on the type of query you're talking about. If there's only one row in the table you're querying then no, I don't think it'll change anything. If you're querying a single row using a primary key it shouldn't change anything. If you're doing an aggregate query, say a sum of a bunch of rows, it also won't improve performance. If you're doing a query on a table with multiple rows and not filtering by a primary key or other unique index then yes, it will improve the query. From: pgsql-admin-owner@postgresql.org [mailto:pgsql-admin-owner@postgresql.org] On Behalf Of Anibal David Acosta Sent: Thursday, December 16, 2010 11:19 AM To: pgsql-admin@postgresql.org Subject: [ADMIN] using limit Hi I really like to do efficient SQL queries so, my question is if I am expecting no more than one row from a select, using the LIMIT 1 could improve the performance? If I use my logic, the LIMIT 1 instruction tell to postgres that stop searching when found 1 record, but maybe it is unnecessary Thanks Anibal ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: using limit @ 2010-12-16 19:46 Michael Holt <michael@aers.ca> parent: Anibal David Acosta <aa@devshock.com> 0 siblings, 0 replies; 4+ messages in thread From: Michael Holt @ 2010-12-16 19:46 UTC (permalink / raw) To: Anibal David Acosta <aa@devshock.com>; pgsql-admin Yes, a limit should speed up your query from the sounds of things. *From:* Anibal David Acosta [mailto:aa@devshock.com] *Sent:* Thursday, December 16, 2010 11:34 AM *To:* 'Michael Holt'; pgsql-admin@postgresql.org *Subject:* RE: [ADMIN] using limit Is a table with 10 million of rows with a primary key but conditions used in select are not part of PK. My table is like this: Column 1 – PK Column 2 – Indexed Column 3 – Indexed Column 2 and Column 3 are Indexed in the same index but they are not mark as unique or PK The Query is like this: Select column1 from myTable where Column2 between X and Y I am expecting just one record *De:* Michael Holt [mailto:michael@aers.ca] *Enviado el:* jueves, 16 de diciembre de 2010 04:23 p.m. *Para:* Anibal David Acosta; pgsql-admin@postgresql.org *Asunto:* RE: [ADMIN] using limit This really depends on the type of query you’re talking about. If there’s only one row in the table you’re querying then no, I don’t think it’ll change anything. If you’re querying a single row using a primary key it shouldn’t change anything. If you’re doing an aggregate query, say a sum of a bunch of rows, it also won’t improve performance. If you’re doing a query on a table with multiple rows and not filtering by a primary key or other unique index then yes, it will improve the query. *From:* pgsql-admin-owner@postgresql.org [mailto: pgsql-admin-owner@postgresql.org] *On Behalf Of *Anibal David Acosta *Sent:* Thursday, December 16, 2010 11:19 AM *To:* pgsql-admin@postgresql.org *Subject:* [ADMIN] using limit Hi I really like to do efficient SQL queries so, my question is if I am expecting no more than one row from a select, using the LIMIT 1 could improve the performance? If I use my logic, the LIMIT 1 instruction tell to postgres that stop searching when found 1 record, but maybe it is unnecessary Thanks Anibal ^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2010-12-16 19:46 UTC | newest] Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2010-12-16 19:18 using limit Anibal David Acosta <aa@devshock.com> 2010-12-16 19:23 ` Michael Holt <michael@aers.ca> 2010-12-16 19:33 ` Anibal David Acosta <aa@devshock.com> 2010-12-16 19:46 ` Michael Holt <michael@aers.ca>
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