On Tue, Oct 1, 2013 at 1:56 PM, Andres Freund <andres@2ndquadrant.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
