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

[Adriano d. S. F. <adr...@gm...>]

Vlad Khorsun wrote:
>> Ann W. Harrison wrote:
>>> Here's the problem I see, and it may exist already.
>>>
>>> Create a table, which creates format 1 for that table.
>>> Store a bunch of records.
>>>
>>> Add a NOT NULL field with a default value of 'ABC',
>>> which creates format 2 for the table.  The new format
>>> includes the default value.
>>>
>>> Now if you read records for that table, the new field's
>>> value is 'ABC'.
>>>
>> That's ok.
>>
>>> Now alter the table, changing the default value to '123',
>>> creating a new format 3 which includes the new default
>>> for that field.
>>>
>>> Read the same records again and the value is probably going
>>> to be '123'.
>>>
>> If the record format is 2, it should return 'ABC'. If the record is updated and written in the 
>> format 3, 'ABC' should be written to the field so it doesn't catch the format 3 value when 
>> reading it.
> 
>     What if record still stored in format 1 ?
> 
Records at format 1 (which does not have the field added in 2) should use the default value stored in format 2. So 'ABC' should be written when updating to format 3 too.


Adriano