From: | mlw <markw(at)mohawksoft(dot)com> |
---|---|
To: | Andrew McMillan <andrew(at)catalyst(dot)net(dot)nz> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Hackers List <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: External search engine, advice |
Date: | 2001-05-20 21:00:31 |
Message-ID: | 3B08306F.E419EB05@mohawksoft.com |
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Lists: | pgsql-hackers |
Andrew McMillan wrote:
>
> Tom Lane wrote:
> >
> > begin;
> > select * from foo where x = functhatreadsbar();
> > update bar ...;
> > select * from foo where x = functhatreadsbar();
> > end;
> >
> > does not give you the desired results.
>
> But why would you be marking the function 'iscachable' if you wanted to see the
> change there?
Because if there is an index on 'x' you would want to use it instead of
performing a full table scan. If table 'foo' has millions of records, and
functhatreadsbar() return one value, an operation that can take milliseconds,
not takes seconds with no benefit.
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