On 22/10/2020 16:49, Amit Langote wrote:
On Tue, Oct 20, 2020 at 9:57 PM Amit Langote <amitlangot...@gmail.com> wrote:
On Mon, Oct 19, 2020 at 8:55 PM Heikki Linnakangas <hlinn...@iki.fi> wrote:
It's probably true that there's no performance gain from initializing
them more lazily. But the reasoning and logic around the initialization
is complicated. After tracing through various path through the code, I'm
convinced enough that it's correct, or at least these patches didn't
break it, but I still think some sort of lazy initialization on first
use would make it more readable. Or perhaps there's some other
refactoring we could do.
So the other patch I have mentioned is about lazy initialization of
the ResultRelInfo itself, not the individual fields, but maybe with
enough refactoring we can get the latter too.
So, I tried implementing a lazy-initialization-on-first-access
approach for both the ResultRelInfos themselves and some of the
individual fields of ResultRelInfo that don't need to be set right
away. You can see the end result in the attached 0003 patch. This
slims down ExecInitModifyTable() significantly, both in terms of code
footprint and the amount of work that it does.
Have you done any performance testing? I'd like to know how much of a
difference this makes in practice.
Another alternative is to continue to create the ResultRelInfos in
ExecInitModify(), but initialize the individual fields in them lazily.
Does this patch become moot if we do the "Overhaul UPDATE/DELETE
processing"?
(https://www.postgresql.org/message-id/CA%2BHiwqHpHdqdDn48yCEhynnniahH78rwcrv1rEX65-fsZGBOLQ%40mail.gmail.com)?
- Heikki
