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Re: [19] CREATE SUBSCRIPTION ... SERVER

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Shlok Kyal <shlok.kyal.oss@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Joe Conway <mail@joeconway.com>, pgsql-hackers@postgresql.org
Date: 2026-03-05T19:00:43Z
Lists: pgsql-hackers 
On Tue, 2026-03-03 at 10:19 -0800, Masahiko Sawada wrote:
> It made me think that it might be
> interesting to implement a FDW that supports only the libpq
> connection
> (i.e., NO HANDLER, NO VALIDATOR, and CONNECTION) as it provides the
> connection management capability useful for subscriptions while users
> can avoid any security risks in postgres_fdw that users might be
> concerned about.

We discussed some similar ideas earlier in the thread. My initial
proposal used special "FOR CONNECTION ONLY" syntax and had special
cases for the FDW.

Tom didn't like the special syntax and catalog work[1], and suggested a
dummy FDW. Ashutosh expressed concern about the scope of a dummy
FDW[2], and suggested that we just rely on postgres_fdw, which is the
current patch. I agree and think it's the right direction.

A new special-purpose FDW might be useful, but I don't understand the
exact use case yet, so I think it's better to leave it to the user to
implement a new FDW that does what they want. (Perhaps special safety
rules, etc.)

Regards,
	Jeff Davis

[1]
https://www.postgresql.org/message-id/172273.1693403385%40sss.pgh.pa.us
[2]
https://www.postgresql.org/message-id/CAExHW5uCzS-VeSYQHTHxFSdQik-f_O892xmzrzm2fuO+ro+otA@mail.gmail.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Document new catalog columns, missed in commit 8185bb5347.

  2. Refactor to remove ForeignServerName().

  3. GetSubscription(): use per-object memory context.

  4. Fix dependency on FDW's connection function.

  5. ALTER SUBSCRIPTION ... SERVER test.

  6. Fix pg_dump for CREATE FOREIGN DATA WRAPPER ... CONNECTION.

  7. Clean up postgres_fdw/t/010_subscription.pl.

  8. CREATE SUBSCRIPTION ... SERVER.

  9. Allow upgrades to preserve the full subscription's state.