Re: Buffer usage in EXPLAIN and pg_stat_statements (review)

On Wed, Oct 14, 2009 at 9:56 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Itagaki Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
>> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> 2. I do not understand the stuff with propagating counts into the top
>>> instrumentation node.
>
>> It is required by contrib/pg_stat_statements. EXPLAIN wants per-node
>> accumulation, but pg_stat_statements wants the total number.
>
> Well, you need to find another way or risk getting the patch rejected
> altogether.  Those global variables are the weakest part of the whole
> design, and I'm not going to commit a patch that destabilizes the entire
> system for the sake of a debatable "requirement" of a contrib module.
>
> If you went with the alternative definition I suggested (don't reset the
> static counters, so that every node includes its children's counts) then
> the behavior you want would fall out automatically.  Or, at the price of
> running both resettable and non-resettable static counters, you could
> have pg_stat_statements obtain totals that are independent of any
> particular instrumentation node.

I am marking this patch as Returned with Feedback. I hope that it
will be resubmitted for a future CommitFest, because I think this
could be pretty interesting feature.

...Robert