From: | "Joe Conway" <joseph(dot)conway(at)home(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards |
Date: | 2001-06-23 19:11:37 |
Message-ID: | 00b101c0fc18$53ed01f0$0205a8c0@jecw2k1 |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> For extra credit ;-) ... if you'd like to learn a little bit about the
> optimizer, think about teaching clause_selectivity() in
> optimizer/path/clausesel.c how to estimate the selectivity of these new
> expression nodes. In the case where the argument is a boolean column
> that we have statistics for, it should be possible to derive the correct
> answer (including accounting for NULLs). If the argument is more
> complex than that, you probably can't do anything really intelligent,
> but you could handwave away NULLs and then compute the appropriate
> function of the clause_selectivity() of the argument.
Attached is my initial attempt to teach clause_selectivity about BooleanTest
nodes, for review and comment. Please let me know if I'm headed in the right
direction.
Thanks,
Joe
Attachment | Content-Type | Size |
---|---|---|
booltestsel_00.diff | application/octet-stream | 5.9 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2001-06-23 20:58:37 | Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards |
Previous Message | Olivier PRENANT | 2001-06-23 18:07:36 | Re: psql+openssl+uniware7 |