Re: [HACKERS] [PATCH] A hook for session start

On Mon, Nov 20, 2017 at 2:56 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> =?UTF-8?Q?Fabr=C3=ADzio_de_Royes_Mello?= <fabriziomello(at)gmail(dot)com> writes:
> > typedef enum
> > {
> > ClientBackendProcess = -1,
> > CheckerProcess = 0,
> > BootstrapProcess,
>
> Uh, why would you do that (start from -1)? It makes it impossible to
> build an array indexed by the enum, which might be useful --- converting
> enum values to strings is one obvious application. Breaks your
> "NUM_PROCTYPES" thing, too.
>

I agree... I just copy and paste AuxProcType with some kind of
generalization.

> What I'd do is probably
>
> UnknownProcess = 0,
> PostmasterProc,
> StandaloneBackendProc,
> ClientBackendProc,
> BootstrapProc,
> ...
> NUM_PROCTYPES /* Must be last! */
>
> The value of reserving "UnknownProcess = 0" is that a freshly started
> process would be correctly not-identified if the variable starts out 0.
> (I'd be rather tempted to teach fork_process to reset it to 0 immediately
> after forking, too, so that postmaster children couldn't inadvertently
> retain the PostmasterProc setting.)
>

Makes sense...

> I'm not entirely sure whether standalone backends ought to get their
> own code, or whether it's better for them to share ClientBackendProc.
> It's something we'd have to work out as we went through the code
> making the patch. How many places would want to distinguish, versus
> how many would have to test for two values?
>

Maybe for the first version we use just "ClientBackendProc" and refactor
all the code necessary to generalize AuxProcType. Then we can step into
into. Seems reasonable?

> > extern ProcType MyProcType;
>
> "PGProcType", maybe? "ProcType" alone seems pretty generic.
> "ServerProcType" is another possibility for the typedef name,
> to emphasize that what we are classifying is the postmaster
> and its children.
>

"ServerProcType" seems a good name.

Due to some "Blackfriday" commitments I'll be able to work again with this
patch on next week.

Regards,

--
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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