From: Vik Fearing <vik@2ndquadrant.fr>
To: Filip Rembiałkowski <filip.rembialkowski@gmail.com>
To: Brendan Jurd <direvus@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: proposal: make NOTIFY list de-duplication optional
Date: Sun, 7 Feb 2016 11:54:04 +0100
Message-ID: <56B7224C.4090807@2ndquadrant.fr> (raw)
In-Reply-To: <CAP_rww=xRoBfbAqkywCHTs3jDxF9zknh1zLkrJKxZGykRtEHQg@mail.gmail.com>
References: <CAP_rwwn2z0gPOn8GuQ3qDVS5+HgEcG2EzEOyiJtcA=vpDEhoCg@mail.gmail.com>
<CA+TgmoYiKedu0vUXFQHKpJ1COmT7sNJd2KOLLtXQTQc6Ztgkug@mail.gmail.com>
<7647.1454723392@sss.pgh.pa.us>
<CADxJZo16qGNKhROpM-7hg6xgxNMarh2kBW=2suOCv+5EbPUfsw@mail.gmail.com>
<CAP_rww=xRoBfbAqkywCHTs3jDxF9zknh1zLkrJKxZGykRtEHQg@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-hackers>
On 02/07/2016 03:42 AM, Filip Rembiałkowski wrote:
> +1
>
> ... and a patch (only adding ALL keyword, no hash table implemented yet).
Please stop top-posting, it's very disruptive. My comments are below,
where they belong.
> On Sat, Feb 6, 2016 at 2:35 PM, Brendan Jurd <direvus@gmail.com> wrote:
>> On Sat, 6 Feb 2016 at 12:50 Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>>
>>> Robert Haas <robertmhaas@gmail.com> writes:
>>>> I agree with what Merlin said about this:
>>>>
>>>> http://www.postgresql.org/message-id/CAHyXU0yoHe8Qc=yC10AHU1nFiA1tbHsg+35Ds-oEueUapo7t4g@mail.gmail....
>>>
>>> Yeah, I agree that a GUC for this is quite unappetizing.
>>
>>
>> How would you feel about a variant for calling NOTIFY?
>>
>> The SQL syntax could be something like "NOTIFY [ALL] channel, payload" where
>> the ALL means "just send the notification already, nobody cares whether
>> there's an identical one in the queue".
>>
>> Likewise we could introduce a three-argument form of pg_notify(text, text,
>> bool) where the final argument is whether you are interested in removing
>> duplicates.
>>
>> Optimising the remove-duplicates path is still probably a worthwhile
>> endeavour, but if the user really doesn't care at all about duplication, it
>> seems silly to force them to pay any performance price for a behaviour they
>> didn't want, no?
On 02/07/2016 03:42 AM, Filip Rembiałkowski wrote:
> +1
>
> ... and a patch (only adding ALL keyword, no hash table implemented yet).
I only read through the patch, I didn't compile it or test it, but I
have a few comments:
You left the duplicate behavior with subtransactions, but didn't mention
it in the documentation. If I do NOTIFY DISTINCT chan, 'msg'; then I
expect only distinct notifications but I'll get duplicates if I'm in a
subtransaction. Either the documentation or the code needs to be fixed.
I seem to remember some discussion about not using DEFAULT parameters in
system functions so you should leave the old function alone and create a
new function with your use_all parameter. I don't recall the exact
reason why so hopefully someone else will enlighten me.
There is also no mention in the documentation about what happens if I do:
NOTIFY ALL chan, 'msg';
NOTIFY ALL chan, 'msg';
NOTIFY DISTINCT chan, 'msg';
NOTIFY ALL chan, 'msg';
Without testing, I'd say I'd get two messages, but it should be
explicitly mentioned somewhere.
--
Vik Fearing +33 6 46 75 15 36
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: vik@2ndquadrant.fr, filip.rembialkowski@gmail.com, direvus@gmail.com, tgl@sss.pgh.pa.us, robertmhaas@gmail.com
Subject: Re: proposal: make NOTIFY list de-duplication optional
In-Reply-To: <56B7224C.4090807@2ndquadrant.fr>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox