Re: [Firebird-devel] Adding NOT NULL fields with DEFAULT

[Vlad K. <hv...@us...>]

>>> Only simple expressions are allowed for DEFAULT now, with means more problems if complex expressions are allowed.
>> 
>>     Is standard allow to reference fileds from the same table in default expression ?
>>  
> I don't know, but apparent don't make sense. But I see no problem in a function call being used, for example.

    Make sense or not - doesn't matter. If something is allowed then there will be user which can't live without it ;)

    Your method will not work if expressions dependent on values of another fields of the same table is allowed
and we should investigate it at first.
 
>>> Initial verification to implement the thing in a good way has to populate the fields in DFW, after the new format has 
>>> been created. This does not solve the problem completely. There can be snapshot transactions that see the new 
>>> field but can't see its default value.
>> 
>>     It is performance killer "solution" and i don't like it very much.
>> 
>>> Related to above, I tried to update records in system transaction. Initially works in some condition, but I don't 
>>> think it's good way to go either.
>> 
>>     Don't do it. System transaction should be read-only.
>> 
> Formats are updated using it. ;-)

    Yes, and it creates some bad issues. No need to introduce new problems.

Regards,
Vlad