Re: Some ExecSeqScan optimizations

Hi Amit,

On Fri, Jan 10, 2025 at 7:22 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
>
> On Fri, Jan 10, 2025 at 7:36 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > On Fri, 10 Jan 2025 at 22:53, Vladlen Popolitov
> > <v(dot)popolitov(at)postgrespro(dot)ru> wrote:
> > > In case of query
> > > select count(*) from test_table where a_1 = 1000000;
> > > I would expect increase of query time due to additional if...else . It
> > > is not clear
> > > what code was eliminated to decrease query time.
> >
> > Are you talking about the code added to ExecInitSeqScan() to determine
> > which node function to call? If so, that's only called during executor
> > startup. The idea here is to reduce the branching during execution by
> > calling one of those special functions which has a more specialised
> > version of the ExecScan code for the particular purpose it's going to
> > be used for.
>
> Looks like I hadn't mentioned this key aspect of the patch in the
> commit message, so did that in the attached.

Thanks for updating the patch. While seeing the patch, the es_epq_active
confused me a little bit mostly because its name, a field name ending with
"active" typically suggests a boolean value, but here it is not, should we
change it to sth like es_epqstate? However this is not related to this patch,
I can start a new thread if you think this is worth a patch.

There is one tiny indent issue(my IDE does this automatically), which I
guess you will fix before committing.

- EPQState *epqstate;
+ EPQState *epqstate;

>
> Vladlen, does what David wrote and the new commit message answer your
> question(s)?
>
> --
> Thanks, Amit Langote

--
Regards
Junwang Zhao