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:mich...@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-ow...@postgresql.org [mailto:pgsql-admin-ow...@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
