Re: Buffer usage in EXPLAIN and pg_stat_statements (review)

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.

regards, tom lane