From: | Mike Mascari <mascarm(at)mascari(dot)com> |
---|---|
To: | Ron Peterson <rpeterson(at)yellowbank(dot)com> |
Cc: | Robert Deme <RDeme(at)tornado(dot)ro>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: |
Date: | 2000-06-15 16:13:04 |
Message-ID: | 39490090.8F1A8CA8@mascari.com |
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Lists: | pgsql-general |
Ron Peterson wrote:
>
> Robert Deme wrote:
> >
> > Hello!!
> >
> > in flagship ( a variant of clipper for unix , http://www.wgs.com/) it is
> > an interesting statement "seek eval" ; it scans the index and for every
> > position it evaluates a block of code/ function until the function
> > return true .
> > is in postgresql an internal mechanism or a way to use the index when
> > selecting records with conditions like function(index_expression) =
> > value ?
>
> I'm not sure I understand the question. There are a large number of
> functions built in to PostgreSQL that you can use in your queries. Plus
> you can define your own functions in SQL, C, or other languages. If
> you're talking about something else, maybe send an example.
I think he's asking about functional indexes. PostgreSQL does
support functional indexes. For example:
stocks=# create table test (field text);
CREATE
stocks=# create index k_test1 on test ( lower(field) );
CREATE
Then a
SELECT * FROM test WHERE lower(field) = 'mike'
would use the index (if the optimizer so chooses) to locate the
appropriate records.
Hope that helps,
Mike Mascari
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