New & changed scan - null values fix

[darrell-k]

Issue #1493

Also fix inconsistent behaviour when setting previously populated columns to null in a new & changed scan - depending on the user's tagging software, we might not get tags set to null at all.

Should we be extending the new list of nullable columns $nullableColumns?

This could fix other reported inconsistencies in the N&C scan, so I think it's worth backporting to 9.0.

I also found we need to issue an update() to the TrackPersistent object, otherwise the changed columns remain "dirty" and never get committed to the database. I don't know if this has never worked, or if there have been recent(ish) changes to the underlying libraries.

[michaelherger]

I'm sorry, I'm out for a week. This might have to wait a few days...

[darrell-k]

I'm sorry, I'm out for a week. This might have to wait a few days...

No problem.

[darrell-k]

@mikeysas in the meantime you could replace your Slim/Schema.pm (in 9.1) with this https://raw.githubusercontent.com/LMS-Community/slimserver/326f506cf8bf13adc76d67c0220d38067db2f813/Slim/Schema.pm and see if it helps.

[mikeysas]

@mikeysas in the meantime you could replace your Slim/Schema.pm (in 9.1) with this https://raw.githubusercontent.com/LMS-Community/slimserver/326f506cf8bf13adc76d67c0220d38067db2f813/Slim/Schema.pm and see if it helps.

I just did a quick test using the Album Rescan and MBID's were updated in tracks_persistent and play stats updated. I will do some more testing as I update more tags and let you know if I see an issue, but looks good to me. Thx!