| From: | Benedikt Grundmann <bgrundmann(at)janestreet(dot)com> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, david(at)fetter(dot)org, Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, jgh(at)wizmail(dot)org, itparanoia(at)gmail(dot)com, GavinFlower(at)archidevsys(dot)co(dot)nz, david(dot)g(dot)johnston(at)gmail(dot)com |
| Subject: | Re: More thorough planning for OLAP queries (was: [PATCH] Equivalence Class Filters) |
| Date: | 2015-12-30 08:12:04 |
| Message-ID: | CADbMkNMXG83KHEpv=ZLBgHf4CqsLWp=ODEMC-Hw3G6cBH2O2SQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Dec 30, 2015 at 7:16 AM, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
wrote:
>
> A number of ideas were suggested on the other thread about how we might go
> about solving this problem. In [3] Simon talked about perhaps enabling
> extra optimisations when the planner sees that the plan will cost more than
> some given threshold. That's perhaps an option, but may not work well for
> optimisations which must take place very early in planning, for example [4].
>
A small tweak on 3 to deal with 4. If the returned plan cost is quite high
(say you estimate minutes+) you could just restart planning from scratch
with all costly planning enabled, because even in the worst case (that is
the additional options don't find a better plan), the total planning cost
won't matter much in the grand scheme of things.
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