Default order by timestamp to ensure early versions are cleaned

[owenr]

Addresses #699: 'cleaner' intermittently fails to keep the latest version because the query assumes but does not enforce chronological order. Postgresql exposes the assumption by failing the tests but not 100% of the time.

I had considered ordering by id instead of timestamp but was unsure about the reliability of that approach.

[bronson]

Very nice. Personally I find ordering by ID more reliable since timestamps can end up equal.

[owenr]

How about order(PaperTrail.timestamp_field, :id) ?

[bronson]

Sure, that fixes the equality problem. Does it have a benefit over sorting by id only?

[owenr]

If someone changed the assignment of IDs in their database I could see it being a problem, but having checked it looks like the table will always be created with monotonically-increasing IDs. @jaredbeck, any preference?

[jaredbeck]

The documentation for the :keeping option says:

• :keeping - An integer indicating the number of versions to be kept for
  each item per date. Defaults to 1.

Can you add something about how the one that's kept is the most recent?

For the sort order, I'd suggest order(PaperTrail.timestamp_field, :id) because it just makes sense to use timestamps for a chronological ordering. Scott makes a good point about timestamp equality, and adding the id as a secondary sort should give us deterministic results in that case.

Finally, please add a line to the changelog, under 5.0.0 -> Fixed. Thanks!

[owenr]

Done.

[jaredbeck]

Thanks!

[batter]

I believe we need should update this to use PaperTrail::Version.timestamp_sort_order. Apologies for the delayed response, just saw this, I'm happy to work that in tomorrow when I get a chance.

[batter]

Made the aforementioned update: c200721

[jaredbeck]

Thanks Ben. Good catch.