From: | amit sehas <cun23(at)yahoo(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Cursor behavior |
Date: | 2011-12-21 16:44:59 |
Message-ID: | 1324485899.94928.YahooMailClassic@web160506.mail.bf1.yahoo.com |
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Thread: | |
Lists: | pgsql-hackers |
It seems that the task of fetching next n results without moving the cursor seems like too complicated to implement for any query that has
even a little bit of complication in it...
--- On Wed, 12/21/11, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> From: Robert Haas <robertmhaas(at)gmail(dot)com>
> Subject: Re: [HACKERS] Cursor behavior
> To: "amit sehas" <cun23(at)yahoo(dot)com>
> Cc: pgsql-hackers(at)postgresql(dot)org
> Date: Wednesday, December 21, 2011, 8:43 AM
> On Thu, Dec 15, 2011 at 4:15 PM, amit
> sehas <cun23(at)yahoo(dot)com>
> wrote:
> > I had a question about the cursor internals
> implementation. When you Fetch next 'n' results without
> moving the cursors, is this kind of functionality
> implemented by firstly executing the whole query and then
> moving the cursor over the results, or are the movements
> done on active database lookups, moving forward and
> backward...
>
> I think it depends on the query. For example, I
> believe that a query
> involving writeable CTEs will be run to completion before
> returning
> any results, but I believe that a seqscan will not.
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>
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