| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
| Cc: | Alan Williams <alan_williams(at)affymetrix(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Inheritance & Indexes |
| Date: | 2003-06-25 14:31:03 |
| Message-ID: | 25979.1056551463@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> writes:
> I *think* 7.4 may be smarter about
> implying these conditions as well.
Not really. AFAIR the Append-style plan is the only thing you can get
out of the planner for inheritance trees. This works well enough for
restriction clauses like "id = constant" (since those get pushed down to
the member tables, much as with UNION ALL), but it just isn't gonna be
efficient for join situations. And I can't see any realistic way for
the planner to realize that only some pairs of child tables need be
joined.
I think the decision to use an inheritance tree for performance reasons
(as opposed to any logical necessity) was probably not a good one.
It'd be better to store all the data in one big table and use partial
indexes for faster access to subsets.
regards, tom lane
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