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Re: Really dumb planner decision

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: Matthew Wakeling <matthew(at)flymine(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Really dumb planner decision
Date: 2009-04-16 13:49:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
> On Thu, Apr 16, 2009 at 8:05 AM, Matthew Wakeling <matthew(at)flymine(dot)org> wrote:
>> That solves the problem. So, a view is treated as a subquery then?

> no...the view is simply inlined into the query (think C macro) using
> the rules.  You just bumped into an arbitrary (and probably too low)
> limit into the number of tables the planner can look at in terms of
> optimizing certain types of plans.

Bear in mind that those limits exist to keep you from running into
exponentially increasing planning time when the size of a planning
problem gets big.  "Raise 'em to the moon" isn't really a sane strategy.
It might be that we could get away with raising them by one or two given
the general improvement in hardware since the values were last looked
at; but I'd be hesitant to push the defaults further than that.

			regards, tom lane

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