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From: Pavel Stehule <pavel.stehule@gmail.com>
To: remi duval <remi.duval@cheops.fr>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: proposal: schema variables
Date: Fri, 28 Feb 2020 16:30:28 +0100
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čt 27. 2. 2020 v 15:37 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
napsal:

>
> Hi
>
>
>> 3) Any way to define CONSTANTs ?
>> We already talked a bit about this subject and also Gilles Darold
>> introduces it in this mailing-list topic but I'd like to insist on it.
>> I think it would be nice to have a way to say that a variable should not
>> be changed once defined.
>> Maybe it's hard to implement and can be implemented later, but I just
>> want to know if this concern is open.
>>
>
> I played little bit with it and I didn't find any nice solution, but maybe
> I found the solution. I had ideas about some variants, but almost all time
> I had a problem with parser's shifts because all potential keywords are not
> reserved.
>
> last variant, but maybe best is using keyword WITH
>
> So the syntax can looks like
>
> CREATE [ TEMP ] VARIABLE varname [ AS ] type [ NOT NULL ] [ DEFAULT
> expression ] [ WITH [ OPTIONS ] '(' ... ')' ] ]
>
> What do you think about this syntax? It doesn't need any new keyword, and
> it easy to enhance it.
>
> CREATE VARIABLE foo AS int DEFAULT 10 WITH OPTIONS ( CONSTANT);
>

After some more thinking and because in other patch I support syntax CREATE
TRANSACTION VARIABLE ... I change my opinion and implemented support for
syntax CREATE IMMUTABLE VARIABLE for define constants.

See attached patch

Regards

Pavel


>
> ?
>
> Regards
>
> Pavel
>
>
>


Attachments:

  [application/gzip] schema-variables-20200228.patch.gz (64.6K, 3-schema-variables-20200228.patch.gz)
  download

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