Subject: Re: proposal: schema variables
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From: Gilles Darold <gilles.darold@dalibo.com>
Message-ID: <c48dc141-776e-2284-15fa-3863f7b6a1b4@dalibo.com>
Date: Wed, 1 Nov 2017 00:02:26 +0100
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Le 31/10/2017 à 23:36, Gilles Darold a écrit :
> Le 31/10/2017 à 22:28, srielau a écrit :
>> Pavel,
>>
>> There is no
>> DECLARE TEMP CURSOR
>> or
>> DECLARE TEMP variable in PLpgSQL
>> and
>> CREATE TEMP TABLE has a different meaning from what I understand you
>> envision for variables.
>>
>> But maybe I'm mistaken. Your original post did not describe the entire
>> syntax:
>> CREATE [TEMP] VARIABLE [IF NOT EXISTS] name AS type 
>>   [ DEFAULT expression ] [[NOT] NULL]
>>   [ ON TRANSACTION END { RESET | DROP } ]
>>   [ { VOLATILE | STABLE } ];
>>
>> Especially the TEMP is not spelled out and how its presence affects or
>> doesn't ON TRANSACTION END.
>> So may be if you elaborate I understand where you are coming from.
> I think that the TEMP keyword can be removed. If I understand well the
> default scope for variable is the session, every transaction in a
> session will see the same value. For the transaction level, probably the
> reason of the TEMP keyword, I think the [ ON TRANSACTION END { RESET |
> DROP } ] will allow to restrict the scope to this transaction level
> without needing the TEMP keyword. When a variable is created in a
> transaction, it is temporary if "ON TRANSACTION END DROP" is used
> otherwise it will persist after the transaction end. I guess that this
> is the same as using TEMP keyword?

I forgot to say that in the last case the DECLARE statement can be used
so I don't see the reason of this kind of "temporary" variables.

Maybe the variable object like used in DB2 and defined in document :
https://www.ibm.com/support/knowledgecenter/en/SSEPEK_11.0.0/sqlref/src/tpc/db2z_sql_createvariable.html
could be enough to cover our needs.


-- 
Gilles Darold
Consultant PostgreSQL
http://dalibo.com - http://dalibo.org


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