Re: cost of CREATE VIEW ... AS SELECT DISTINCT

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