From: T E Schmitz <mailreg@numerixtechnology.de>
To: Scott Marlowe <smarlowe@g2switchworks.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: cost of CREATE VIEW ... AS SELECT DISTINCT
Date: Tue, 29 Mar 2005 11:07:20 +0100
Message-ID: <424928D8.7060705@numerixtechnology.de> (raw)
In-Reply-To: <1112047463.22988.25.camel@state.g2switchworks.com>
References: <42487A6D.6020506@numerixtechnology.de>
<1112047463.22988.25.camel@state.g2switchworks.com>
Hello Scott,
Scott Marlowe wrote:
> On Mon, 2005-03-28 at 15:43, T E Schmitz wrote:
>
>>How expensive would it be to maintain the following VIEW:
>>
>>CREATE VIEW origin AS SELECT DISTINCT origin FROM transaktion
>>
>>if there is in index on transaktion.origin; the table transaktion has
>>thousands of records and there are only a few distinct origin?
>
>
> The cost will only be encurred when running the view. if you want
> materialized views (which WOULD have maintenance costs) you'll have to
Thank you for the pointer - that might come in handy for another scenario.
> The cost of executing that view should be the same as the cost of
> running the query by hand.
I did an EXPLAIN ANALYZE and a sequential scan was carried out despite
the index I had on the column. Maybe this is because I only have very
few records in my test DB.
Would the "SELECT DISTINCT origin" always cause a sequential table scan
regardless whether there is an index on the origin column or not?
--
Regards/Gruß,
Tarlika Elisabeth Schmitz
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To: pgsql-sql@postgresql.org
Cc: mailreg@numerixtechnology.de, smarlowe@g2switchworks.com
Subject: Re: cost of CREATE VIEW ... AS SELECT DISTINCT
In-Reply-To: <424928D8.7060705@numerixtechnology.de>
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