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From: Michel Pelletier <[email protected]>
To: Tom Lane <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: Using Expanded Objects other than Arrays from plpgsql
Date: Sun, 20 Oct 2024 20:29:13 -0700
Message-ID: <CACxu=vLXvpzN4X3k+9jsMt6ujuOvFVUSkA80t_cROSsF4y2jQQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CACxu=vJaKFNsYxooSnW1wEgsAO5u_v1XYBacfVJ14wgJV_PYeg@mail.gmail.com>
	<[email protected]>

On Sun, Oct 20, 2024 at 10:13 AM Tom Lane <[email protected]> wrote:

>
> I'm not sure.  It seems certain that if the object is already expanded
> (either R/W or R/O), the paths for that in plpgsql_exec_function could
> be taken regardless of its specific type.
>


> But it seems like we could get an easy win by adjusting
> plpgsql_exec_function along the lines of
>
> l. 549:
> -                    if (!var->isnull && var->datatype->typisarray)
> +                    if (!var->isnull)
>
> l. 564:
> -                        else
> +                        else if (var->datatype->typisarray)
>
> How far does that improve matters for you?
>

I tried this change and couldn't get it to work, on the next line:

if (!var->isnull)
{
    if (VARATT_IS_EXTERNAL_EXPANDED_RW(DatumGetPointer(var->value)))

var->value might not be a pointer, as it seems at least from my gdb
scratching, but say an integer.  This segfaults on non-array but
non-expandable datum.

I guess this gets back into knowing if a flat thing is expandable or not.
I'm going to spend some more time looking at it, I haven't been in this
corner of Postgres before.

Another comment that caught my eye was this one:

https://github.com/postgres/postgres/blob/master/src/pl/plpgsql/src/pl_exec.c#L8304

Not sure what the implication is there.

-Michel

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