From: Vitalii Tymchyshyn <tivv00@gmail.com>
To: Merlin Moncure <mmoncure@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Claudio Freire <klaussfreire@gmail.com>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Shouldn't we have a way to avoid "risky" plans?
Date: Fri, 25 Mar 2011 11:43:14 +0200
Message-ID: <4D8C63B2.1060800@gmail.com> (raw)
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24.03.11 20:41, Merlin Moncure написав(ла):
> 2011/3/24 Віталій Тимчишин<tivv00@gmail.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.
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Subject: Re: Shouldn't we have a way to avoid "risky" plans?
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