Horton

Re: Optimize LISTEN/NOTIFY

Joel Jacobson <joel@compiler.org>

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From: "Joel Jacobson" <joel@compiler.org>
To: "Chao Li" <li.evan.chao@gmail.com>
Cc: "Tom Lane" <tgl@sss.pgh.pa.us>, "Thomas Munro" <thomas.munro@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, "Heikki Linnakangas" <hlinnaka@iki.fi>, "Rishu Bagga" <rishu.postgres@gmail.com>
Date: 2025-09-25T21:13:31Z
Lists: pgsql-hackers

Commits

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

  1. Optimize LISTEN/NOTIFY via shared channel map and direct advancement.

  2. Fix incorrect logic for caching ResultRelInfos for triggers

Attachments

On Thu, Sep 25, 2025, at 10:25, Chao Li wrote:
> Hi Joel,
>
> Thanks for the patch. After reviewing it, I got a few comments.

Thanks for reviewing!

>> On Sep 25, 2025, at 04:34, Joel Jacobson <joel@compiler.org> wrote:
> 1.
...
> Can we define the new one after STARTUP_PROGRESS_TIMEOUT to try to 
> preserve the existing enum value?

Fixed.

> 2.
...
> I think we should add one more table to make the comment to align with 
> last line’s comment.

Fixed.

> 3.
...
> I know compiler will auto initiate notify_latency_target to 0. But all 
> other global and static variables around are explicitly initiated, so 
> it would look better to assign 0 to it, which just keeps coding style 
> consistent.

Fixed.

> 4.
...
> Should we avid duplicate timeout to be enabled? Now, whenever a 
> duplicate notification is avoid, a new timeout is enabled. I think we 
> can add another variable to remember if a timeout has been enabled.

Hmm, I don't see how duplicate timeout could happen?

Once we decide to defer the wakeup, wakeup_pending_flag remains set,
which avoids further signals from notifiers, so I don't see how we could
re-enter ProcessIncomingNotify(), since notifyInterruptPending is reset
when ProcessIncomingNotify() is called, and notifyInterruptPending is
only set when a signal is received (or set directly when in same
process).

New patch attached with 1-3 fixed.

/Joel