| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(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: | 2013-10-01 17:56:33 |
| Message-ID: | 20131001175633.GA5408@awork2.anarazel.de |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
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?
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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