Migrate: Duplicate entries in url_alias after update migrations I have term and node migrations from wprdpress to drupal 8 (with pathauto module enabled). I set the url alias in the migration templates like:

process:
  path/alias: source_path
  path/pathauto:
    plugin: default_value
    default_value: 0


Setting the path that way works fine on importing content with drush mi term. But when I update the terms with drush mi term --update a new (the same) path gets inserted into the url_alias table. For example the term with tid 1 gets imported once and updated 2 times there will be the following aliases in url_alias table:

select * from url_alias where source = '/taxonomy/term/1';
+------+------------------+---------------+----------+
| pid  | source           | alias         | langcode |
+------+------------------+---------------+----------+
| 1514 | /taxonomy/term/1 | /term-1-alias | de       |
| 2731 | /taxonomy/term/1 | /term-1-alias | de       |
| 3632 | /taxonomy/term/1 | /term-1-alias | de       |
+------+------------------+---------------+----------+


BTW: I have pathauto module enabled, but uninstalling it results in the same behavior.
Looks like a bug in the core path module: https://www.drupal.org/node/2350135