Comment 1 for bug 672762

This is really interesting and might contribute to the problem.

When selecting playlists, crates or other root models, BaseSqlModel::select() is called 3-4 times. This is inefficient for <LibraryFeature>TableModels that hold large data sets.

How to reproduce:
* Add a qDebug() to BaseSqlModel::select()
* Execute Mixxx and click on some playlists, crates, etc

This is probably because Mixxx does also call restoreSearch() on sidebar item changes which fires a select as well.