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In-Reply-To: <2351536.1729735831@sss.pgh.pa.us>
From: Michel Pelletier <pelletier.michel@gmail.com>
Date: Thu, 31 Oct 2024 16:41:48 -0700
Message-ID: <CACxu=vK9zZRVasn3Pmn3tbe8z715rPWiXtQ=rKzF9_KbUcH2QA@mail.gmail.com>
Subject: Re: Using Expanded Objects other than Arrays from plpgsql
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@lists.postgresql.org
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Here's two backtraces from gdb from this function:

CREATE OR REPLACE FUNCTION test2(graph matrix)
    RETURNS bigint LANGUAGE plpgsql AS
    $$
    BEGIN
    perform set_element(graph, 1, 1, 1);
    RETURN nvals(graph);
    end;
    $$;

https://gist.githubusercontent.com/michelp/d02e3e300710443454357222077f9ded=
/raw/86d9c2c3de3f9b4740065a7b8c29a3e1c54b1cac/gistfile1.txt

Both traces are in that file split on the hyphens line 44.  I'm still
puzzling it out, could it have something to do with the volatility of the
functions?  I'm not entirely clear on how to interpret function volatility
with expanded objects, nvals is STRICT, but set_element is STABLE.  I think
my logic there was because it's a mutation.  This is likely another
misunderstanding of mine.

-Michel

On Wed, Oct 23, 2024 at 7:10=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Michel Pelletier <pelletier.michel@gmail.com> writes:
> > On Wed, Oct 23, 2024 at 8:21=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wr=
ote:
> >> Another thing that confuses me is why there's a second flatten_matrix
> >> operation happening here.  Shouldn't set_element return its result
> >> as a R/W expanded object?
>
> > That confuses me too, and my default assumption is always that I'm doin=
g
> it
> > wrong.  set_element does return a R/W object afaict, here is the return=
:
> > https://github.com/OneSparse/OneSparse/blob/main/src/matrix.c#L1726
>
> Hmph.  That seems right.  Can you add errbacktrace() to your logging
> ereports, in hopes of seeing how we're getting to flatten_matrix?
> Or break there with gdb for a more complete/reliable stack trace.
>
>                         regards, tom lane
>

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<div dir=3D"ltr">Here&#39;s two backtraces from gdb from this function:<div=
><br></div><div>CREATE OR REPLACE FUNCTION test2(graph matrix)<br>=C2=A0 =
=C2=A0 RETURNS bigint LANGUAGE plpgsql AS<br>=C2=A0 =C2=A0 $$<br>=C2=A0 =C2=
=A0 BEGIN<br>=C2=A0 =C2=A0 perform set_element(graph, 1, 1, 1);<br>=C2=A0 =
=C2=A0 RETURN nvals(graph);<br>=C2=A0 =C2=A0 end;<br>=C2=A0 =C2=A0 $$;<br><=
/div><div><br></div><div><a href=3D"https://gist.githubusercontent.com/mich=
elp/d02e3e300710443454357222077f9ded/raw/86d9c2c3de3f9b4740065a7b8c29a3e1c5=
4b1cac/gistfile1.txt">https://gist.githubusercontent.com/michelp/d02e3e3007=
10443454357222077f9ded/raw/86d9c2c3de3f9b4740065a7b8c29a3e1c54b1cac/gistfil=
e1.txt</a><br></div><div><br></div><div>Both traces are in that file split =
on the hyphens line 44.=C2=A0 I&#39;m still puzzling it out, could it have =
something to do with the volatility of the functions?=C2=A0 I&#39;m not ent=
irely clear on how to interpret function volatility with expanded=C2=A0obje=
cts, nvals is STRICT, but set_element is STABLE.=C2=A0 I think my logic the=
re was because it&#39;s a mutation.=C2=A0 This is likely another misunderst=
anding of mine.</div><div><br></div><div>-Michel</div></div><br><div class=
=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Oct 23, 2024=
 at 7:10=E2=80=AFPM Tom Lane &lt;<a href=3D"mailto:tgl@sss.pgh.pa.us">tgl@s=
ss.pgh.pa.us</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" styl=
e=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);paddin=
g-left:1ex">Michel Pelletier &lt;<a href=3D"mailto:pelletier.michel@gmail.c=
om" target=3D"_blank">pelletier.michel@gmail.com</a>&gt; writes:<br>
&gt; On Wed, Oct 23, 2024 at 8:21=E2=80=AFAM Tom Lane &lt;<a href=3D"mailto=
:tgl@sss.pgh.pa.us" target=3D"_blank">tgl@sss.pgh.pa.us</a>&gt; wrote:<br>
&gt;&gt; Another thing that confuses me is why there&#39;s a second flatten=
_matrix<br>
&gt;&gt; operation happening here.=C2=A0 Shouldn&#39;t set_element return i=
ts result<br>
&gt;&gt; as a R/W expanded object?<br>
<br>
&gt; That confuses me too, and my default assumption is always that I&#39;m=
 doing it<br>
&gt; wrong.=C2=A0 set_element does return a R/W object afaict, here is the =
return:<br>
&gt; <a href=3D"https://github.com/OneSparse/OneSparse/blob/main/src/matrix=
.c#L1726" rel=3D"noreferrer" target=3D"_blank">https://github.com/OneSparse=
/OneSparse/blob/main/src/matrix.c#L1726</a><br>
<br>
Hmph.=C2=A0 That seems right.=C2=A0 Can you add errbacktrace() to your logg=
ing<br>
ereports, in hopes of seeing how we&#39;re getting to flatten_matrix?<br>
Or break there with gdb for a more complete/reliable stack trace.<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 regards, tom lane<br>
</blockquote></div>

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