Re: Index usage question

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От Norbert Zoltan Toth
Тема Re: Index usage question
Дата
Msg-id 004701c1358f$d003ccf0$11278a89@cern.ch
обсуждение исходный текст
Ответ на Index usage question  (Jefim Matskin <mjefim@sphera.com>)
Список pgsql-general
> The fastest operation for the number of rows returned by the query is
> attempted -- granted that it may not always work but an index scan isn't
> always the best answer for large sets of data..You actually have more
> overhead using an index in some situations.
>
> You said you enter some rows, but how many rows got returned by your
query?
>
> Though I'm not sure, PG might not treat that 1 as the integer 1, since
it's
> in single quotes.. The index was on an integer field, perhaps that is part
> of the problem too...
>
> -Mitch
>
> > I have experienced the following problem, maybe they are related:
> >
> > I create a table with
> >     create table test (id int, name char(10));
> >
> > then I create an index on it with
> >     create index test_idx on test (id);
> >
> > After populating my table, the query
> >     select id from test where id='1';
> >
> > uses index scan.
> >
> > However when I only create the index AFTER inserting rows into the
table,
> > the index is not being used for the evaluation,
> > even if I run vacuum / vaccum analyze on test;
> >
> > I would also appreciate some help with this.
>
>
>


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