Subject RE: [firebird-support] Re: UPDATE to same record causing heavy disk I/O
Author Leyne, Sean
> Right. When we were working on InterBase 1.1 (I think) a friend of Jim's
> suggested using deltas for back versions to save space.  He's still a friend, but
> that feature was a real trial to implement and debug, partly because we ran
> out of bits in the record header.

With today's unlimited availability of disk space and silly-low cost per GB for storage, would an argument to dispense with the delta and simply store a full copy of the record (not including BLOB) be worthy of discussion?

I wonder if the economics which required the creation of delta's has been overtaken and the cost of merging deltas is no longer worth it.

I know that Jim has mentioned that in his later db engine he has adopted a reverse approach which has the latest version stored in full and for transactions required back versions responsible processing the deltas. In this way, the latest version of the row are always complete so that the back versions can be dropped very efficiently.