Re: Buffer pool statistics in Explain Analyze

ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> I think there two independent items here:
> [1] Should we add those statistics to pg_stat_statements or not?
> [2] Should we add those statistics to EXPLAIN ANALYZE or not?

> I wanted to have [1] and proposed it, but it is rejected from 8.4.
> However, the reason is not because we have little demand for it,
> but [1] and [2] are mixed in the patch and they are bad designed.

No, I think you misunderstood me entirely. The reason that I rejected
those parts of the patch is that I think the statistics that are
available are wrong/useless. If the bufmgr.c counters were really good
for something they'd have been exposed long since (and we'd probably
never have built a lot of the other stats collection infrastructure).

The EXPLAIN ANALYZE code you submitted is actually kinda cute, and
I'd have had no problem with it if I thought it were displaying
numbers that were useful and unlikely to be obsoleted in future
releases. The work that needs to be done is on collecting the
numbers more than displaying them.

regards, tom lane