| From: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PATCH] Equivalence Class Filters |
| Date: | 2015-12-07 16:55:15 |
| Message-ID: | 5665B9F3.80109@BlueTreble.com |
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| Lists: | pgsql-hackers |
On 12/7/15 10:44 AM, Simon Riggs wrote:
> There are many optimizations we might adopt, yet planning time is a
> factor. It seems simple enough to ignore more complex optimizations if
> we have already achieved a threshold cost (say 10). Such a test would
> add nearly zero time for the common case. We can apply the optimizations
> in some kind of ordering depending upon the cost, so we are careful to
> balance the cost/benefit of trying certain optimizations.
Unfortunately I've seen a lot of millisecond queries that have 6 figure
estimates, due to data being in cache. So I'm not sure how practical
that would be.
Maybe a better starting point would be a planner timeout.
I definitely agree we need some method to limit planning time when
necessary (ie: OLTP). Without that we'll never be able to start testing
more complex optimizations.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
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