Re: query progress bar

On Tue, May 17, 2005 at 09:01:14AM +1000, Timothy Smith wrote:
> 
> is it possible to mke a progress bar for queries? say i have a query 
> that will take 20 seconds, i'd like to give some feed back to users on 
> how long this will take.
It is sure possible but it is not very useful because

- you will need the number of rows in the result
- which could be gotten by "select count(*) from ... where ..."
- which, however, takes pretty much the same time as the query itself
- which is in part due to PostgreSQL's MVCC nature
- which cannot be sped up by using an index
- because current tuple visibility is not stored in the index 
- and doing so would create overhead for insert/update

Karsten
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