| From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
|---|---|
| To: | Bo Lorentsen <bl(at)netgroup(dot)dk> |
| Cc: | Michael Fuhr <mike(at)fuhr(dot)org>, Russell Simpkins <russellsimpkins(at)hotmail(dot)com>, pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: Number of rows in a cursor ? |
| Date: | 2005-08-25 13:10:21 |
| Message-ID: | 20050825131021.GC15100@wolff.to |
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| Lists: | pgsql-sql |
On Thu, Aug 25, 2005 at 08:51:59 +0200,
Bo Lorentsen <bl(at)netgroup(dot)dk> wrote:
> Michael Fuhr wrote:
>
> >Right -- when you open a cursor PostgreSQL doesn't know how many
> >rows it will return. PostgreSQL selects a query plan based on an
> >*estimate* of how many rows the query will return, but until you
> >fetch all the rows you can't know for sure how many rows there will
> >be.
> >
> >
> So if i make a but data set as result of a cursor I only "pay" for the
> rows I actually fetch ?
There is usually some overhead for set up, though I believe quick starting
plans are favored for cursor queries.
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