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From: Ron Johnson <ronljohnsonjr@gmail.com>
Date: Fri, 15 May 2026 18:56:46 -0400
Message-ID: 
 <CANzqJaBVAykTGq8j-gijJS-L0bK7duyO-k2xKgr8ZmO9mqxXMw@mail.gmail.com>
Subject: Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL
To: "pgsql-general@postgresql.org" <pgsql-general@postgresql.org>
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Frank,

Why doesn't the shared OID space make cross-database queries possible?  SQL
Server does it, so the idea isn't that far-fetched.

On Fri, May 15, 2026 at 6:18=E2=80=AFPM Frank Heikens <frank@elevarq.com> w=
rote:

>
> Hi Shivam,
>
> Thank you for your feedback.
>
> One important difference is terminology.
>
> In MySQL, CREATE DATABASE and CREATE SCHEMA are essentially the same
> command, so what MySQL calls a =E2=80=9Cdatabase=E2=80=9D is effectively =
a schema
> (namespace).
>
> PostgreSQL also supports querying across schemas natively, so the same
> functionality is already available when the objects are in the same
> PostgreSQL database.
>
> In PostgreSQL, a database is a true isolation boundary with its own
> catalogs and connection context. Because of this design, direct joins
> across databases are not supported. When this is required, postgres_fdw i=
s
> the recommended solution.
>
> So for most MySQL users, the equivalent approach in PostgreSQL is to use
> multiple schemas within a single database rather than multiple databases.
>
> Best regards,
> Frank Heikens
>
>
>
> > On May 15, 2026, at 3:06=E2=80=AFPM, Shivam Pandey <shivampandey91199@g=
mail.com>
> wrote:
> >
> > =EF=BB=BF
> > Hello PostgreSQL Team,
> >
> > I would like to share feedback from a developer perspective regarding
> cross-database querying in PostgreSQL.
> >
> > One feature that many developers appreciate in MySQL is the ability to
> directly query and join tables across multiple databases within the same
> server instance. This approach becomes very useful in real-world situatio=
ns
> where applications need to access shared or distributed data quickly and
> efficiently.
> >
> > In PostgreSQL, achieving similar functionality often requires additiona=
l
> setup using extensions such as postgres_fdw or dblink. While these
> solutions are powerful and architecturally clean, they can feel complex f=
or
> developers who are building applications rapidly or migrating from system=
s
> like MySQL.
> >
> > It would be valuable if PostgreSQL could provide a more
> developer-friendly and simplified native approach for cross-database
> querying while still maintaining PostgreSQL=E2=80=99s strong isolation an=
d security
> principles.
> >
> > Possible improvements could include:
> >
> > 1)Simpler syntax for cross-database joins
> > 2) Easier configuration for trusted local databases
> > 3) Built-in lightweight federation support
> > 4) Better onboarding documentation for multi-database use cases
> >
> > PostgreSQL is already one of the most powerful and respected databases
> in the industry. Enhancing developer convenience in this area could make
> adoption even smoother for many teams.
> >
> > Thank you for your incredible work and continuous innovation.
> >
> > Best Regards,
> > Shivam Pandey
>


--=20
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!

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<div dir=3D"ltr"><div>Frank,</div><div><br></div><div>Why doesn&#39;t the s=
hared OID space make cross-database queries possible?=C2=A0 SQL Server does=
 it, so the idea isn&#39;t that far-fetched.</div><br><div class=3D"gmail_q=
uote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Fri, M=
ay 15, 2026 at 6:18=E2=80=AFPM Frank Heikens &lt;<a href=3D"mailto:frank@el=
evarq.com">frank@elevarq.com</a>&gt; wrote:<br></div><blockquote class=3D"g=
mail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204=
,204,204);padding-left:1ex"><br>
Hi Shivam,<br>
<br>
Thank you for your feedback.<br>
<br>
One important difference is terminology.<br>
<br>
In MySQL, CREATE DATABASE and CREATE SCHEMA are essentially the same comman=
d, so what MySQL calls a =E2=80=9Cdatabase=E2=80=9D is effectively a schema=
 (namespace).<br>
<br>
PostgreSQL also supports querying across schemas natively, so the same func=
tionality is already available when the objects are in the same PostgreSQL =
database.<br>
<br>
In PostgreSQL, a database is a true isolation boundary with its own catalog=
s and connection context. Because of this design, direct joins across datab=
ases are not supported. When this is required, postgres_fdw is the recommen=
ded solution.<br>
<br>
So for most MySQL users, the equivalent approach in PostgreSQL is to use mu=
ltiple schemas within a single database rather than multiple databases.<br>
<br>
Best regards,<br>
Frank Heikens<br>
<br>
<br>
<br>
&gt; On May 15, 2026, at 3:06=E2=80=AFPM, Shivam Pandey &lt;<a href=3D"mail=
to:shivampandey91199@gmail.com" target=3D"_blank">shivampandey91199@gmail.c=
om</a>&gt; wrote:<br>
&gt; <br>
&gt; =EF=BB=BF<br>
&gt; Hello PostgreSQL Team,<br>
&gt; <br>
&gt; I would like to share feedback from a developer perspective regarding =
cross-database querying in PostgreSQL.<br>
&gt; <br>
&gt; One feature that many developers appreciate in MySQL is the ability to=
 directly query and join tables across multiple databases within the same s=
erver instance. This approach becomes very useful in real-world situations =
where applications need to access shared or distributed data quickly and ef=
ficiently.<br>
&gt; <br>
&gt; In PostgreSQL, achieving similar functionality often requires addition=
al setup using extensions such as postgres_fdw or dblink. While these solut=
ions are powerful and architecturally clean, they can feel complex for deve=
lopers who are building applications rapidly or migrating from systems like=
 MySQL.<br>
&gt; <br>
&gt; It would be valuable if PostgreSQL could provide a more developer-frie=
ndly and simplified native approach for cross-database querying while still=
 maintaining PostgreSQL=E2=80=99s strong isolation and security principles.=
<br>
&gt; <br>
&gt; Possible improvements could include:<br>
&gt; <br>
&gt; 1)Simpler syntax for cross-database joins<br>
&gt; 2) Easier configuration for trusted local databases<br>
&gt; 3) Built-in lightweight federation support<br>
&gt; 4) Better onboarding documentation for multi-database use cases<br>
&gt; <br>
&gt; PostgreSQL is already one of the most powerful and respected databases=
 in the industry. Enhancing developer convenience in this area could make a=
doption even smoother for many teams.<br>
&gt; <br>
&gt; Thank you for your incredible work and continuous innovation.<br>
&gt; <br>
&gt; Best Regards,<br>
&gt; Shivam Pandey <br>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=
=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_s=
ignature"><div dir=3D"ltr">Death to &lt;Redacted&gt;, and butter sauce.<div=
>Don&#39;t boil me, I&#39;m still alive.<br><div><div>&lt;Redacted&gt; lobs=
ter!</div></div></div></div></div></div>

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