Re: EXPLAIN BUFFERS

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> > Should I add countBufferUsage boolean arguments to all places
> > doInstrument booleans are currently used? This requires several
> > minor modifications of codes in many places.
>
> Pushing extra arguments around would create overhead of its own ...
> overhead that would be paid even when not using EXPLAIN at all.

I cannot understand what you mean... The additional argument should
not be a performance overhead because the code path is run only once
per execution. Instrumentation structures are still not allocated
in normal or EXPLAIN queries; allocated only in "EXPLAIN ANALYZE".

Or, are you suggesting to separate buffer counters with Instrumentation
structure? It still requires extra arguments, but it could minimize the
overhead when we use EXPLAIN ANALYZE without BUFFERS. However, we need
additional codes around InstrStartNode/InstrStopNode calls.

Or, are you complaining about non-performance overheads,
something like overheads of code maintenance?

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center