Re: Speed. My guess is that given an indexed fixed-width CHAR field I should be able to get acceptable speed on lookups. All I need to do is decide on the maximum total number of objects and the maximum number of versions and I should be able to pick a field width. I'll be using MySQL and my memory is that MySQL indexes CHARs just as well as it does INTs.

Re: Querying. I think you misunderstood (or I did). In my planned implementation the current version would always exist without an appeneded ",version". Thus, selecting the current version is just:

SELECT * FROM foo WHERE id = "1024"

No sub-select required! And selecting version N is simply:

SELECT * FROM foo WHERE id = "1024,N"

Now, I may still need an extra column to store the current version number but as long as it isn't needed on every select and every join I'll be happy.

I think you're correct about collecting aggregate information across versions being hard. But I don't anticipate needing to do that very often, if at all.

-sam

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