Re: How to interpret this explain analyse?

"Joost Kraaijeveld" <J.Kraaijeveld@Askesis.nl> writes:
> I cannot change the query (it is geneated by a tool called Clarion) but it something like (from the
psqlodbc_xxx.log):
> "...
> declare SQL_CUR01 cursor for
> SELECT A.ordernummer, B.klantnummer FROM "orders" A LEFT OUTER JOIN "klt_alg" B ON A.Klantnummer=B.Klantnummer ORDER
BYA.klantnummer; 
> fetch 100 in SQL_CUR01;
> ..."

Well, the planner does put some emphasis on startup time when dealing
with a DECLARE CURSOR plan; the problem you face is just that that
correction isn't large enough.  (From memory, I think it optimizes on
the assumption that 10% of the estimated rows will actually be fetched;
you evidently want a setting of 1% or even less.)

We once talked about setting up a GUC variable to control the percentage
of a cursor that is estimated to be fetched:
http://archives.postgresql.org/pgsql-hackers/2000-10/msg01108.php
It never got done but that seems like the most reasonable solution to
me.

            regards, tom lane