From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Kevin Grittner <kgrittn(at)ymail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: logical changeset generation v6.1 |
Date: | 2013-10-02 14:56:38 |
Message-ID: | CA+TgmoZ29eTR2nfTQiiNwD7nBh7MASH=qWuafhwA5PhVewo_Xw@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Oct 1, 2013 at 1:56 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2013-10-01 10:07:19 -0400, Robert Haas wrote:
>> - It seems that HeapSatisfiesHOTandKeyUpdate is now
>> HeapSatisfiesHOTandKeyandCandidateKeyUpdate. Considering I think this
>> was merely HeapSatisfiesHOTUpdate a year ago, it's hard not to be
>> afraid that something unscalable is happening to this function. On a
>> related node, any overhead added here costs broadly; I'm not sure if
>> there's enough to worry about.
>
> Ok, I had to think a bit, but now I remember why I think these changes
> are not really problem: Neither the addition of keys nor candidate keys
> will add any additional comparisons since the columns compared for
> candidate keys are a subset of the set of key columns which in turn are a
> subset of the columns checked for HOT. Right?
TBH, my primary concern was with maintainability more than performance.
On performance, I think any time you add code it's going to cost
somehow. However, it might not be enough to care about.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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