On Sun, May 24, 2009 at 2:42 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
I'm not sure how to make the planner aware of these correlations. Is there something inherently flawed with this design? It seems pretty close to the one on the Varlena website [1].
It still feels like this schema design is obscuring correlations that
the planner needs to know about in order to make decent estimates.
I'm not sure how to make the planner aware of these correlations. Is there something inherently flawed with this design? It seems pretty close to the one on the Varlena website [1].
You mentioned earlier that the seemingly unrelated question_ids were
linked via a common submission_id. I wonder whether it's possible to
query using the submission_id instead?
Well, I do join the different response tables [text/date/etc] together via the submission_id. However, in order to be able to apply the where clauses appropriately, I have to limit the responses to the appropriate question_id's. Would it matter to push that requirement down to the where clause instead of part of the join clause?
David
1. http://www.varlena.com/GeneralBits/110.php
