Subject: Re: proposal: make NOTIFY list de-duplication optional
To: =?UTF-8?Q?Filip_Rembia=c5=82kowski?= <filip.rembialkowski@gmail.com>
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Cc: Pgsql Hackers <pgsql-hackers@postgresql.org>
From: Vik Fearing <vik@2ndquadrant.fr>
Message-ID: <56B764BA.9070800@2ndquadrant.fr>
Date: Sun, 7 Feb 2016 16:37:30 +0100
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On 02/07/2016 04:00 PM, Filip Rembiałkowski wrote:
> On Sun, Feb 7, 2016 at 11:54 AM, Vik Fearing <vik@2ndquadrant.fr> wrote:
>> 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.
> 
> I'm quite new to this; how do I pinpoint proper OID for a new catalog
> object (function, in this case)?
> Is there a better way than browsing fmgr files and guessing next available oid?

There is a shell script called `unused_oids` in src/include/catalog/.

>> 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.
> 
> If it's four separate transactions, LISTEN'er should get four.

The question was for one transaction, I should have been clearer about that.

> If it's in one transaction,  LISTEN'er should get three.

This is surprising to me, I would think it would get only two.  What is
your rationale for three?

Compare with the behavior of:

    select 1
    union all
    select 1
    union distinct
    select 1
    union all
    select 1;
-- 
Vik Fearing                                          +33 6 46 75 15 36
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support


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