Re: Not HOT enough

On Wed, Nov 23, 2011 at 9:44 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Wed, Nov 23, 2011 at 3:20 PM, Alvaro Herrera
> <alvherre@commandprompt.com> wrote:
>>
>> Excerpts from Robert Haas's message of mié nov 23 12:15:55 -0300 2011:
>>
>>> > And it effects shared catalogs only, which are all low traffic anyway.
>>>
>>> I think "low traffic" is the key point.  I understand that you're not
>>> changing the VACUUM behavior, but you are making heap_page_prune_opt()
>>> not do anything when a shared catalog is involved.  That would be
>>> unacceptable if we expected shared catalogs to be updated frequently,
>>> either now or in the future, but I guess we don't expect that.
>>
>> Maybe not pg_database or pg_tablespace and such, but I'm not so sure
>> about pg_shdepend.  (Do we record pg_shdepend entries for temp tables?)
>
> Normal catalog access does not use HOT and never has.
>

I don't understand that. We started with the simplified assumption
that HOT can skip catalog tables, but later that was one of the
pre-conditions Tom spelled out to accept HOT patch because his view
was if this does not work for system tables, it probably does not work
at all.

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB     http://www.enterprisedb.com