Re: [Boost-users] [multi_index] Serialization problemwithmulti_indexcontainer

From: John Reid (john.reid_at_[hidden])
Date: 2006-04-04 06:09:59

JOAQUIN LOPEZ MU?Z wrote:
> So far so good. When saving and subsequently loading
> this container, Boost.MultiIndex guarantees that the
> traversal order of *every* index is preserved. Now,
> suppose serialization were implemented the naive way,
> that is, by just saving the elements as they are
> visited by the first index and loading through the
> first index again, just as you're doing in your
> workaround (no offense meant by the use of the
> word "naive", of course.) If you examine the process
> carefully, you can see that, when performed this
> way, index #0 is correctly replicated, but the
> resulting order of the loaded index #1 is
> 
>   (0,1,0), (1,1,1), (2,1,2)
> 
> which does not match the original. This is why
> Boost.MultiIndex saves, additionally to the elements,
> enough extra information to restore index traversal
> orders in those cases where such order is not
> univocally determined (ordered non-unique,
> sequenced and random-access indices.) And when applying
> this extra information, the kind of sanity check
> you've been bitten by is routinely performed. I
> hope I've made myself clear, sorry for the long
> explanation. 
> 

Thanks for the very clear explanation. "Bitten by" is a kind way of 
saying "corrected by"!

John.