[GSoC] migration

[Bradley Giesbrecht]

> On Aug 11, 2017, at 12:46 PM, Umesh Singla <umeshksingla at macports.org> wrote:
> 
> Hi Josh,
> 
>         And then again, I am sensing a confusion with the idea of
>         snapshot with Josh, like when he says "remove ports when they
>         are no longer referenced by any snapshot".
> 
> 
>     What confusion exactly? A snapshot is simply a set of ports (by
>     which I mean rows in the 'ports' table, with a unique combination of
>     name,version,revision,variants). When nothing references a row any
>     more, it needs to be deleted.
> 
> 
> By 'ports', do you mean 'registry.ports' table? If yes, then I disagree. It's actually 'registry.snapshot_ports' table. A snapshot has nothing to do with the original registry "tables".
> 
> That was a suggested design; if you're already doing it differently then I guess you don't need a design. I disagree with the last sentence though, a snapshot can be viewed as precisely the state of the original tables at a previous time.
> 
> This is on the lines what I had in mind regarding a snapshot.
> 
> Also, we are not using version and revision. Even going by the literal meaning of a snapshot, it should not have a key or id linked to something that can change over time. It's simply the present state.
> 
> The row in the ports table would not change over time, it would simply persist until no longer needed. If we ever get the ability to install old versions then that information would come in handy.
> 
> I meant when the port gets updates, the row in the 'ports' table will change but not in 'snapshot_ports' table because for a particular snapshot, the state has changed. But I think it's clear now.
> 
> And yes, version and revision can help in restoring older versions of ports present in older snapshots.
>  
> Later, I am planning to keep information on the manual portgroups in the snapshot, if there are any.
> 
> What would this information be used for?
>  
> I am under the impression that a user can categorize and classify the ports into portgroups, so it should be better if we migrate them too. Though, it seems highly 

Checkout "man portgroup”, I think your understanding may not be 100% correct. Portgroups simply provide a way for port authors to include common code in there ports.

Perhaps you are thinking that we would need to snapshot portgroup files if we where to ever support installing older versions of software. In that case you would be correct, the portgroup files would need to match the version of the portfile.

—
Brad