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From: Petr Kada <p3tr.kada@gmail.com>
Date: Fri, 27 Jun 2025 16:45:02 +0200
Message-ID: <CABRqZWU6fK_eUt-5=1JGJ_AVtQBwTkN5S=rbRyUD0=-pwyRMaA@mail.gmail.com>
Subject: Re: Figure out nullability of query parameters
To: Giacomo Cavalieri <giacomo.cavalieri@icloud.com>
Cc: pgsql-general@lists.postgresql.org
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Hi,
I have no idea how/if this is possible using the query protocol but I would
try to parse the INSERT statement to get the table and columns names and
then look up whether they are nullable in the information schema (
https://www.postgresql.org/docs/current/infoschema-columns.html)

Petr

On Fri, Jun 27, 2025 at 4:31=E2=80=AFPM Giacomo Cavalieri <
giacomo.cavalieri@icloud.com> wrote:

> Hello!
> I=E2=80=99m Giacomo, I=E2=80=99m the maintainer of <
> https://github.com/giacomocavalieri/squirrel>, a tool that can generate
> type safe bindings to run and decode the results of Postgres queries. It
> does that by implementing the extended query protocol, which, among other
> things, returns the OIDs of the query parameters=E2=80=99 types.
> This is really handy and has worked great so far but I=E2=80=99m running =
into some
> rough edges when it comes to the nullability of query parameters.
>
> Take a query like this one:
> ```
> insert into some_table(not_null_col, nullable_column)
> values ($1, $2)
> ```
> It would be really handy to know that `$1` is being used as a non nullabl=
e
> value, while `$2` could actually be null. Can this already be achieve
> today, or would there be a way to surface this kind of information for
> query parameters in the extended protocol?
>
> Sorry if this is not the proper list, I=E2=80=99m very new to all of this=
 :)
> Thanks!
>
> Giacomo
>

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<div dir=3D"ltr">Hi,=C2=A0<br>I have no idea how/if this is possible using =
the query protocol but I would try to parse the INSERT statement to get the=
 table and columns names and then look up whether they are nullable in the =
information schema (<a href=3D"https://www.postgresql.org/docs/current/info=
schema-columns.html">https://www.postgresql.org/docs/current/infoschema-col=
umns.html</a>)<br><br>Petr</div><br><div class=3D"gmail_quote gmail_quote_c=
ontainer"><div dir=3D"ltr" class=3D"gmail_attr">On Fri, Jun 27, 2025 at 4:3=
1=E2=80=AFPM Giacomo Cavalieri &lt;<a href=3D"mailto:giacomo.cavalieri@iclo=
ud.com">giacomo.cavalieri@icloud.com</a>&gt; wrote:<br></div><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid=
 rgb(204,204,204);padding-left:1ex"><div>Hello!<div>I=E2=80=99m Giacomo, I=
=E2=80=99m the maintainer of &lt;<a href=3D"https://github.com/giacomocaval=
ieri/squirrel" target=3D"_blank">https://github.com/giacomocavalieri/squirr=
el</a>&gt;,=C2=A0a tool that can generate type safe bindings to run and dec=
ode the results of Postgres queries. It does that by implementing the exten=
ded query protocol, which, among other things, returns the OIDs of the quer=
y parameters=E2=80=99 types.</div><div>This is really handy and has worked =
great so far but I=E2=80=99m running into some rough edges when it comes to=
 the nullability of query parameters.</div><div><br></div><div>Take a query=
 like this one:</div><div>```</div><div>insert into some_table(not_null_col=
, nullable_column)</div><div>values ($1, $2)</div><div>```</div><div>It wou=
ld be really handy to know that `$1` is being used as a non nullable value,=
 while `$2` could actually be null. Can this already be achieve today, or w=
ould there be a way to surface this kind of information for query parameter=
s in the extended protocol?</div><div><br></div><div>Sorry if this is not t=
he proper list, I=E2=80=99m very new to all of this :)</div><div>Thanks!</d=
iv><div><br></div><div>Giacomo</div></div></blockquote></div>

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