| From: | Robert Creager <Robert_Creager(at)LogicalChaos(dot)org> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Michael Fuhr <mike(at)fuhr(dot)org>, PGPerformance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Index isn't used during a join. |
| Date: | 2006-01-12 04:20:46 |
| Message-ID: | 20060111212046.200f3e55@thunder.logicalchaos.org |
| Views: | Whole Thread | Raw Message | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
When grilled further on (Wed, 11 Jan 2006 10:33:03 -0500),
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> confessed:
> The planner understands about transitivity of equality, ie given a = b
> and b = c it can infer a = c. It doesn't do any such thing for
> inequalities though, nor does it deduce f(a) = f(b) for arbitrary
> functions f. The addition Michael suggested requires much more
> understanding of the properties of the functions in your query than
> I think would be reasonable to put into the planner.
>
OK. I think reached a point that I need to re-organize how the data is stored,
maybe ridding myself of the schema and switching entirely to views. At that
point, I likely could rid myself of the function (unmunge_time) I'm using, and
work with times and doy fields.
Thanks,
Rob
--
21:17:00 up 4 days, 13:43, 9 users, load average: 2.02, 2.18, 2.23
Linux 2.6.12-12-2 #4 SMP Tue Jan 3 19:56:19 MST 2006
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2006-01-12 04:33:23 | Re: Stable function being evaluated more than once in a single query |
| Previous Message | K C Lau | 2006-01-12 03:49:16 | Re: indexes on primary and foreign keys |