Re: [GUSDEV] PK constraints for version tables

[Steve F. <sfi...@pc...>]

yes, i guess so.

steve

Deborah Pinney wrote:

> You mean drop the uniqueness constraint for the original 
> PK+modification_date?
> Steve Fischer wrote:
>
>> how about just dropping the uniqueness constraint of the modification 
>> date?
>>
>> steve
>>
>> Chris Sarnowski wrote:
>>
>>>
>>> I can't speak for GUS needs in this particular case, but I've had 
>>> the  same issue in other systems. Deborah is correct in that these 
>>> fields  are not right for PK. The question is how important it is to 
>>> preserve  exact order of the changes to the data. If it's not 
>>> critical you  could just drop the PK. If it is (or even if it's not 
>>> but you believe  in the rule "every table must have a PK"), then you 
>>> should use a  surrogate key from a sequence. In practice, at least, 
>>> the sequence  values increase monotonically so changes to a record 
>>> that occur  multiple times with the same modification date can still 
>>> be ordered  correctly.
>>> I prefer the latter, in general, but I suppose adding a new 
>>> surrogate  key field to all version tables in GUS would be a pretty 
>>> big deal.
>>>
>>> Just my thoughts.
>>> -Chris Sarnowski
>>>
>>> On Oct 21, 2005, at 11:07 AM, Deborah Pinney wrote:
>>>
>>>> I suggest that we drop the uniqueness constraint for PKs of 
>>>> version  tables. PKs for these tables consist of the original PK 
>>>> and the  modification date. Rapid computation can result in 
>>>> uniqueness  copnstraint violations that are not remedied by date 
>>>> format  changes. There doesn't seem to be a purpose in having 
>>>> these  constraints for any of the version tables and dropping the  
>>>> constraints would not result in the loss of information or change  
>>>> query results. I don't know if there is implicit indexing on these  
>>>> keys but I wonder if this could be handled using explicit indexing.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>>
>>
>>
>>
>>
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>
>
>
>
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