Drupal Core's Migrate API maintains an internal table mapping unique source ids to destination ids. This is usually done via a database table that holds the field values that together uniquely identify a source row and the matching destination id of the entity in Drupal.
Looking at a Recent log messages report of one of our Drupal 8 instaces, I came across this error message:
If you need to support obscure URI schemes in your Drupal 8 instance and you're getting error messages about invalid URI schemes, this post is for you.
Suppose you have a view and want to dynamically alter the number of results shown by the view based on the view arguments.