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From: Corey Huinker <corey.huinker@gmail.com>
Date: Tue, 16 Jun 2026 14:08:51 -0400
Message-ID: 
 <CADkLM=dxe8NbQu4RNi2OFXpaRKdpS0-CHGm6Mqtf_rW155BM4g@mail.gmail.com>
Subject: Re: use of SPI by postgresImportForeignStatistics
To: Robert Haas <robertmhaas@gmail.com>
Cc: Etsuro Fujita <etsuro.fujita@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
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On Tue, Jun 16, 2026 at 10:34=E2=80=AFAM Robert Haas <robertmhaas@gmail.com=
> wrote:

> On Tue, Jun 16, 2026 at 8:04=E2=80=AFAM Etsuro Fujita <etsuro.fujita@gmai=
l.com>
> wrote:
> > I thought it would be a good idea to use
> > pg_restore_attribute_stats/pg_restore_relation_stats, because future
> > changes in attribute/relation stats would be absorbed by these
> > functions, which would lower the maintenance cost of this feature.
>
> I agree that we want to reuse code, but this isn't the right way to do
> it. For example, when we want to look up the OID of a relation from
> SQL, we can say 'whatever'::regclass::oid. But when we want to do the
> same thing from C, we don't construct a SELECT statement and execute
> it via SPI. Instead, we have functions like RangeVarGetRelidExtended()
> which provide access to the same underlying functionality more
> directly.
>
> Another example is converting strings to integers. The user calls
> int4in(), which then hands off the call to pg_strtoint32_safe(), which
> can also be called via pg_strtoint32(). Hence, C code should prefer to
> use pg_strtoint32(), while SQL will go through int4in(). Both
> ultimately reach the underlying pg_strtoint32_safe() function, but the
> interfaces are different, so that we can have it be suitable both for
> SQL access and for C access.
>
> This needs to work more like that. The underlying code that ingests
> and updates the stats should be shared, but the stuff that is specific
> to a FunctionCallInfo interface needs to be separated out so that we
> don't need to go through that when calling from C.
>
>
Back when pg_restore_attribute_stats and pg_restore_relation_stats were
being converted from positional to variadic functions, there was a patchset
or two (possibly un-posted, because I couldn't find it just now) where the
variadic functions re-marshalled the arguments into a call to a
fixed-parameter function. If that model were revived, we could have a more
conventional DirectFunctonCall() interface.

Is it possible that we never built a direct function call interface to a
variadic because we never needed one? Perhaps that time is now.

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<div dir=3D"ltr"><br><div class=3D"gmail_quote gmail_quote_container"><div =
dir=3D"ltr" class=3D"gmail_attr">On Tue, Jun 16, 2026 at 10:34=E2=80=AFAM R=
obert Haas &lt;<a href=3D"mailto:robertmhaas@gmail.com">robertmhaas@gmail.c=
om</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margi=
n:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex=
">On Tue, Jun 16, 2026 at 8:04=E2=80=AFAM Etsuro Fujita &lt;<a href=3D"mail=
to:etsuro.fujita@gmail.com" target=3D"_blank">etsuro.fujita@gmail.com</a>&g=
t; wrote:<br>
&gt; I thought it would be a good idea to use<br>
&gt; pg_restore_attribute_stats/pg_restore_relation_stats, because future<b=
r>
&gt; changes in attribute/relation stats would be absorbed by these<br>
&gt; functions, which would lower the maintenance cost of this feature.<br>
<br>
I agree that we want to reuse code, but this isn&#39;t the right way to do<=
br>
it. For example, when we want to look up the OID of a relation from<br>
SQL, we can say &#39;whatever&#39;::regclass::oid. But when we want to do t=
he<br>
same thing from C, we don&#39;t construct a SELECT statement and execute<br=
>
it via SPI. Instead, we have functions like RangeVarGetRelidExtended()<br>
which provide access to the same underlying functionality more<br>
directly.<br>
<br>
Another example is converting strings to integers. The user calls<br>
int4in(), which then hands off the call to pg_strtoint32_safe(), which<br>
can also be called via pg_strtoint32(). Hence, C code should prefer to<br>
use pg_strtoint32(), while SQL will go through int4in(). Both<br>
ultimately reach the underlying pg_strtoint32_safe() function, but the<br>
interfaces are different, so that we can have it be suitable both for<br>
SQL access and for C access.<br>
<br>
This needs to work more like that. The underlying code that ingests<br>
and updates the stats should be shared, but the stuff that is specific<br>
to a FunctionCallInfo interface needs to be separated out so that we<br>
don&#39;t need to go through that when calling from C.<br>
<br></blockquote><div><br></div><div><div>Back when pg_restore_attribute_st=
ats and pg_restore_relation_stats=20
were being converted from positional to variadic functions, there was a=20
patchset or two (possibly un-posted, because I couldn&#39;t find it just=20
now) where the variadic functions re-marshalled the arguments=20
into a call to a fixed-parameter function. If that model were revived, we c=
ould have a more conventional DirectFunctonCall() interface.</div><div><br>=
</div><div>Is it possible that we never built a direct function call interf=
ace to a variadic because we never needed one? Perhaps that time is now.</d=
iv></div></div></div>

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