Re: Is there a way to test for UNASSIGNED in pl/pgsql

2012/10/29 Hannu Krosing <hannu(at)2ndquadrant(dot)com>:
> On 10/29/2012 05:36 PM, Merlin Moncure wrote:
>>
>> On Mon, Oct 29, 2012 at 11:26 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>> wrote:
>>>
>>> Hello
>>>
>>>
>>> 2012/10/29 Hannu Krosing <hannu(at)2ndquadrant(dot)com>:
>>>>
>>>> Hi
>>>>
>>>> Is there a way to test for a variable being unassigned in pl/pgsql ?
>>>>
>>>> I'm writing an audit trigger where I'd like to save full before and
>>>> after images into audit log and I really do not like to do
>>>>
>>>> IF TG_OP IN ('INSERT', 'UPDATE') ...
>>>>
>>>> I'd like rather better if i could just write
>>>>
>>>> IF NEW IS ASSIGNED THEN ...
>>>>
>>>> or even use it straight
>>>>
>>>> null_if_unnasigned(NEW)
>>>>
>>>> overriding
>>>>
>>>> coalesce(NEW, NULL)
>>>>
>>>> for the same purpose would also be ok
>>>>
>>> I don't know about any way, how to do it. It is little bit hard,
>>> because it means test of state plpgsql variable (and plpgsql property)
>>> from SQL expression, and it is not possible from SQL.
>>>
>>> we can design some new variant of IF statement, where parameter is
>>> test of validity some variable instead SQL expression
>>>
>>> some like
>>>
>>> IF DEFINED NEW THEN ...
>>
>> how is that different from SQL coalesce()?
>
> It seems that the "variable is unassigned" comes before SQL has a chance to
> see it.
>
> Would just converting UNDEFINED to NULL be a very bad idea ?

I don't like it

>
> It happens so in many places in SQL queries?
>
> And then in some this NULL is coverted to FALSE :)
>
> --------------------------
> Hannu
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