2011/3/23 Tom Lane <t...@sss.pgh.pa.us> > Claudio Freire <klaussfre...@gmail.com> writes: > > On Wed, Mar 23, 2011 at 5:29 PM, Josh Berkus <j...@agliodbs.com> wrote: > >> On 3/23/11 10:35 AM, Claudio Freire wrote: > >>> * consider plan bailout: execute a tempting plan, if it takes too > >>> long or its effective cost raises well above the expected cost, bail > >>> to a safer plan > > >> That would actually solve this particular case. It would still require > >> us to have some definition of "safer" though. > > > In my head, safer = better worst-case performance. > > If the planner starts operating on the basis of worst case rather than > expected-case performance, the complaints will be far more numerous than > they are today. > > This can se GUC-controllable. Like plan_safety=0..1 with low default value. This can influence costs of plans where cost changes dramatically with small table changes and/or statistics is uncertain. Also this can be used as direct "hint" for such dangerous queries by changing GUC for session/single query.
-- Best regards, Vitalii Tymchyshyn
