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From: Michel Pelletier <pelletier.michel@gmail.com>
Date: Mon, 11 Nov 2024 13:34:06 -0800
Message-ID: <CACxu=vJf2S=ysun_h=zmYNu6oUM47+egbpX5mMC0X9BJK=EQwQ@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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>
> The second expansion in matrix_out happens outside the function, so inside
> there is only the one expansion for both matrix_nvals and the assignment.
> Thank you!  All my tests continue to pass and the change seems to work well.


Hmm, well I spoke to soon looking at the wrong function without an
assignment, I've been down in gdb a bit too much and I got mixed up, here's
another function that wraps it and does an assignment, and it looks like
there is another expansion happening after the nvals but before the
assignment:

create or replace function test_expand_expand(graph matrix) returns matrix
language plpgsql as
    $$
    declare
        nvals bigint = nvals(graph);
    begin
        graph = test_expand(graph);
        return test_expand(graph);
    end;
    $$;

postgres=# select test_expand_expand(a) from test_fixture ;
DEBUG:  matrix_nvals
DEBUG:  DatumGetMatrix
DEBUG:  expand_matrix
DEBUG:  new_matrix
DEBUG:  context_callback_matrix_free
DEBUG:  matrix_nvals
DEBUG:  DatumGetMatrix
DEBUG:  expand_matrix
DEBUG:  new_matrix
DEBUG:  context_callback_matrix_free
DEBUG:  matrix_nvals
DEBUG:  DatumGetMatrix
DEBUG:  expand_matrix
DEBUG:  new_matrix
DEBUG:  context_callback_matrix_free
DEBUG:  matrix_out
DEBUG:  DatumGetMatrix
DEBUG:  expand_matrix
DEBUG:  new_matrix
DEBUG:  context_callback_matrix_free

So going back on the assumption I'm somehow not returning the right
pointer, but digging into the array code I'm pretty sure I'm following the
same pattern and tracing my code path is calling EOHPGetRWDatum when I
return the object, I can't get it to stop on DeleteExpandedObject, so I
don't think plpgsql is deleting it, I'm going to keep investigating, sorry
for the noise.

-Michel

>

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<div dir=3D"ltr"><div dir=3D"ltr"><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding=
-left:1ex">The second expansion in matrix_out happens outside the function,=
 so inside there is only the one expansion for both matrix_nvals and the as=
signment.=C2=A0 Thank you!=C2=A0 All my tests continue to pass and the chan=
ge seems to work well.</blockquote><div><br></div></div><div dir=3D"ltr">Hm=
m, well I spoke to soon looking at the wrong function without an assignment=
, I&#39;ve been down in gdb a bit too much and I got mixed up, here&#39;s a=
nother function that wraps it and does an assignment, and it looks like the=
re is another expansion happening after the nvals but before the assignment=
:<div><br></div><div>create or replace function test_expand_expand(graph ma=
trix) returns matrix language plpgsql as<br>=C2=A0 =C2=A0 $$<br>=C2=A0 =C2=
=A0 declare<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 nvals bigint =3D nvals(graph);<b=
r>=C2=A0 =C2=A0 begin<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 graph =3D test_expand(=
graph);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 return test_expand(graph);<br>=C2=A0=
 =C2=A0 end;<br>=C2=A0 =C2=A0 $$;<br></div><div><br></div><div>postgres=3D#=
 select test_expand_expand(a) from test_fixture ;<br>DEBUG: =C2=A0matrix_nv=
als<br>DEBUG: =C2=A0DatumGetMatrix<br>DEBUG: =C2=A0expand_matrix<br>DEBUG: =
=C2=A0new_matrix<br>DEBUG: =C2=A0context_callback_matrix_free<br>DEBUG: =C2=
=A0matrix_nvals<br>DEBUG: =C2=A0DatumGetMatrix<br>DEBUG: =C2=A0expand_matri=
x<br>DEBUG: =C2=A0new_matrix<br>DEBUG: =C2=A0context_callback_matrix_free<b=
r>DEBUG: =C2=A0matrix_nvals<br>DEBUG: =C2=A0DatumGetMatrix<br>DEBUG: =C2=A0=
expand_matrix<br>DEBUG: =C2=A0new_matrix<br>DEBUG: =C2=A0context_callback_m=
atrix_free<br>DEBUG: =C2=A0matrix_out<br>DEBUG: =C2=A0DatumGetMatrix<br>DEB=
UG: =C2=A0expand_matrix<br>DEBUG: =C2=A0new_matrix<br>DEBUG: =C2=A0context_=
callback_matrix_free<br></div><div><br></div><div>So going back on the assu=
mption I&#39;m somehow not returning the right pointer, but digging into th=
e array code I&#39;m pretty sure I&#39;m following the same pattern and tra=
cing my code path is calling EOHPGetRWDatum when I return the object, I can=
&#39;t get it to stop on DeleteExpandedObject, so I don&#39;t think plpgsql=
 is deleting it, I&#39;m going to keep investigating, sorry for the noise.<=
/div><div><br></div><div>-Michel</div></div><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div class=
=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px =
0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
</blockquote></div></div>
</blockquote></div></div>

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