Horton

Re: LISTEN/NOTIFY testing woes

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <hornschnorter@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org, Martijn van Oosterhout <kleptog@gmail.com>
Date: 2019-11-24T19:04:38Z
Lists: pgsql-hackers 
Mark Dilger <hornschnorter@gmail.com> writes:
> On 11/24/19 10:39 AM, Tom Lane wrote:
>> After sleeping on it, I'm not really happy with what I did in
>> PrepareTransaction (that is, invent a separate PrePrepare_Notify
>> function).  The idea was to keep that looking parallel to what
>> CommitTransaction does, and preserve infrastructure against the
>> day that somebody gets motivated to allow LISTEN or NOTIFY in
>> a prepared transaction.  But on second thought, what would surely
>> happen when that feature gets added is just that AtPrepare_Notify
>> would serialize the pending LISTEN/NOTIFY actions into the 2PC
>> state file.  There wouldn't be any need for PrePrepare_Notify,
>> so there's no point in introducing that.  I'll just move the
>> comment saying that nothing has to happen at that point for NOTIFY.

> I assumed you had factored it out in anticipation of supporting notify
> here in the future.  If you want to backtrack that decision and leave it
> inline, you would still keep the test rather than just a comment, right?

No, there wouldn't be any error condition; that's just needed because the
feature isn't implemented yet.  So I'll leave that alone; the only thing
that needs to happen now in the PREPARE code path is to adjust the one
comment.

			regards, tom lane

Commits

  1. Avoid assertion failure with LISTEN in a serializable transaction.

  2. Stabilize NOTIFY behavior by transmitting notifies before ReadyForQuery.

  3. Stabilize the results of pg_notification_queue_usage().