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From: Michel Pelletier <pelletier.michel@gmail.com>
Date: Mon, 11 Nov 2024 13:27:12 -0800
Message-ID: <CACxu=vKLc6f5N8_DR58LKkE1eohWSxTvThTeGsLm7p7QH1aFBA@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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On Fri, Nov 1, 2024 at 5:53=E2=80=AFPM Michel Pelletier <pelletier.michel@g=
mail.com>
wrote:

> On Fri, Nov 1, 2024 at 3:27=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrote=
:
>
>> Michel Pelletier <pelletier.michel@gmail.com> writes:
>>
>> Here is a v1 patch series that does the first part of what we've been
>> talking about, which is to implement the new optimization rule for
>> the case of a single RHS reference to the target variable.  I'm
>> curious to know if it helps you at all by itself.  You'll definitely
>> also need commit 534d0ea6c, so probably applying these on our git
>> master branch would be the place to start.
>>
>
> I'll apply these tonight and get back to you asap.  There are many
> functions in my API that take only one expanded RHS argument, so I'll loo=
k
> for some cases where your changes reduce expansions when I run my tests.
>

I tested these patches with my test setup and can confirm there is now one
less expansion in this function:

create or replace function test_expand(graph matrix) returns matrix
language plpgsql as
    $$
    declare
        nvals bigint =3D nvals(graph);
    begin
        return graph;
    end;
    $$;

postgres=3D# select test_expand(a) from test_fixture ;
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

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=
.

Looking forward to helping test the support function idea, let me know if
there's anything else I can do to validate the idea.

-Michel

>

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<div dir=3D"ltr"><div dir=3D"ltr">On Fri, Nov 1, 2024 at 5:53=E2=80=AFPM Mi=
chel Pelletier &lt;<a href=3D"mailto:pelletier.michel@gmail.com">pelletier.=
michel@gmail.com</a>&gt; wrote:</div><div class=3D"gmail_quote"><blockquote=
 class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px so=
lid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div dir=3D"ltr">On=
 Fri, Nov 1, 2024 at 3:27=E2=80=AFPM Tom Lane &lt;<a href=3D"mailto:tgl@sss=
.pgh.pa.us" target=3D"_blank">tgl@sss.pgh.pa.us</a>&gt; wrote:<br></div><di=
v class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">M=
ichel Pelletier &lt;<a href=3D"mailto:pelletier.michel@gmail.com" target=3D=
"_blank">pelletier.michel@gmail.com</a>&gt; writes:<br><br>
Here is a v1 patch series that does the first part of what we&#39;ve been<b=
r>
talking about, which is to implement the new optimization rule for<br>
the case of a single RHS reference to the target variable.=C2=A0 I&#39;m<br=
>
curious to know if it helps you at all by itself.=C2=A0 You&#39;ll definite=
ly<br>
also need commit 534d0ea6c, so probably applying these on our git<br>
master branch would be the place to start.<br></blockquote><div><br></div><=
div>I&#39;ll apply these tonight and get back to you asap.=C2=A0 There are =
many functions in my API that take only one expanded RHS argument, so I&#39=
;ll look for some cases where your changes reduce expansions when I run my =
tests.</div></div></div></blockquote><div><br></div>I tested these patches =
with my test setup and can confirm there is now one less expansion in this =
function:<div><br></div><div>create or replace function test_expand(graph m=
atrix) returns matrix language plpgsql as<br>=C2=A0 =C2=A0 $$<br>=C2=A0 =C2=
=A0 declare<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 nvals bigint =3D nvals(graph);<b=
r>=C2=A0 =C2=A0 begin<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 return graph;<br>=C2=
=A0 =C2=A0 end;<br>=C2=A0 =C2=A0 $$;<br><br></div><div>postgres=3D# select =
test_expand(a) from test_fixture ;<br>DEBUG: =C2=A0matrix_nvals<br>DEBUG: =
=C2=A0DatumGetMatrix<br>DEBUG: =C2=A0expand_matrix<br>DEBUG: =C2=A0new_matr=
ix<br>DEBUG: =C2=A0context_callback_matrix_free<br>DEBUG: =C2=A0matrix_out<=
br>DEBUG: =C2=A0DatumGetMatrix<br>DEBUG: =C2=A0expand_matrix<br>DEBUG: =C2=
=A0new_matrix<br>DEBUG: =C2=A0context_callback_matrix_free<br></div><div><b=
r></div><div>The second expansion in matrix_out happens outside the functio=
n, so inside there is only the one expansion for both matrix_nvals and the =
assignment.=C2=A0 Thank you!=C2=A0 All my tests continue to pass and the ch=
ange seems to work well.</div><div><br></div><div>Looking forward to helpin=
g test the support function idea, let me know if there&#39;s anything else =
I can do to validate the idea.</div><div><br></div><div>-Michel</div><block=
quote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1=
px solid rgb(204,204,204);padding-left:1ex">
</blockquote></div></div>

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