From: | Richard Huxton <dev(at)archonet(dot)com> |
---|---|
To: | Amit V Shah <ashah(at)tagaudit(dot)com> |
Cc: | "'pgsql-performance(at)postgresql(dot)org'" <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Do Views execute underlying query everytime ?? |
Date: | 2005-06-21 14:48:39 |
Message-ID: | 42B828C7.8040402@archonet.com |
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Lists: | pgsql-performance |
Amit V Shah wrote:
> Hi all,
>
> I have like a repository table with is very very huge with atleast a few
> hundreds of millions, may be over that. The information is stored in form of
> rows in these tables. I need to make that information wide based on some
> grouping and display them as columns on the screen.
>
> I am thinking of having a solution where I create views for each screen,
> which are just read only.
>
> However, I donot know if the query that creates the view is executed
> everytime I select something from the view. Because if that is the case,
> then I think my queries will again be slow. But if that is the way views
> work, then what would be the point in creating them ..
That's exactly how they work. You'd still want them because they let you
simplify access control (user A can only see some rows, user B can see
all rows) or just make your queries simpler.
Sounds like you want what is known as a "materialised view" which is
basically a summary table that is kept up to date by triggers. You query
the table instead of actually recalculating every time. Perhaps google
for "postgresql materialized view" (you might want a "z" or "s" in
materialised).
--
Richard Huxton
Archonet Ltd
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