[GSoC] migration

[Bradley Giesbrecht]

> On Aug 11, 2017, at 11:16 AM, Joshua Root <jmr at macports.org> wrote:
> 
> On 2017-8-11 21:14 , Umesh Singla wrote:
>> Hi
>>        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.

If that is the case, we can simply (insert into snapshot_ports select * from ports) to create a snapshot. Obviously the snapshot_ports table needs an extra snapshot_id column.

>> 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.

Sounds right.

>> 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?

Sorry, I don’t understand what “manual ports groups” refers to. Maybe I missed an earlier conversation.

—
Brad