On 27 Jan 2010, at 2:00, Yan Cheng Cheok wrote: >>> However, whenever I insert row into measurement table, >> I realize its primary key value is going from 2, 4, 6, 8, >> 10... >>> >>> May I know how can I prevent this? >> >> Apparently nextval on that sequence gets called multiple >> times in your queries. >> > > Do you have any idea why it happens so? It's something you're doing in your queries that causes this. You haven't provided any info about that, so I can only guess. The problem could for example be that you're selecting nextval() of the sequence and then don't fill in the value for that column in a subsequent INSERT, causing the default to call nextval() again. >> Also, is it necessary to create index for >> measurement_id found in measurement's child table? I am >> concern on the read speed. > But... > > measurement table does contains > > CONSTRAINT pk_measurement_id PRIMARY KEY (measurement_id), > > when measurement_0 child table inherits from measurement table, isn't it will inherit PRIMARY KEY (measurement_id)? > > Do I still have to create index for measurement_0.measurement_id ? Ah I see, you were asking about table inheritance. To quote the documentation at http://www.postgresql.org/docs/8.4/interactive/ddl-inherit.html: "All check constraints and not-null constraints on a parent table are automatically inherited by its children. Other types of constraints (unique, primary key, and foreign key constraints) are not inherited." Alban Hertroys -- If you can't see the forest for the trees, cut the trees and you'll see there is no forest. !DSPAM:737,4b60897b10606504295220! -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
