Re: Shouldn't we have a way to avoid "risky" plans?
From:
Vitalii Tymchyshyn <tivv00(at)gmail(dot)com>
To:
Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc:
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Claudio Freire <klaussfreire(at)gmail(dot)com>,
Josh Berkus <josh(at)agliodbs(dot)com>,
postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject:
Re: Shouldn't we have a way to avoid "risky" plans?
24.03.11 20:41, Merlin Moncure написав(ла):
> 2011/3/24 Віталій Тимчишин<tivv00(at)gmail(dot)com>:
>>
>> 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.
> ISTM if you add statistics miss and 'risk margin' to the things the
> planner would have to consider while generating a plan, you are
> greatly increasing the number of plan paths that would have to be
> considered for any non trivial query.
Why so? I simply change cost estimation functions. This won't change
number of pathes.
Best regards, Vitalii Tymchyshyn.
