Re: Query plan with missing timespans

From: Jason Petersen <jason(at)citusdata(dot)com>
To: Andomar <andomar(at)aule(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query plan with missing timespans
Date: 2015-04-22 20:18:40
Message-ID: 4FB6E62B-3876-4D5C-9737-52F23D6693B6@citusdata.com
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> On Apr 22, 2015, at 1:59 PM, Andomar <andomar(at)aule(dot)net> wrote:
>
> Is there a way to tell postgres that a function will always return the same result for the same parameter, within the same transaction?

Yup… read over the Function Volatility Categories <http://www.postgresql.org/docs/9.4/static/xfunc-volatility.html> page and decide which you need. What you’re describing is STABLE (or slightly stricter than STABLE, since STABLE makes that guarantee only for a single statement within a transaction).

--
Jason Petersen
Software Engineer | Citus Data
303.736.9255
jason(at)citusdata(dot)com

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