text: MERGE analytics.user
  USING (
      SELECT DISTINCT
          name
          ,email
          ,'author' AS user_type
      FROM analytics.author
      UNION
      SELECT DISTINCT
          name
          ,email
          ,'committer' AS user_type
      FROM analytics.committer
  )
  ON FALSE
  WHEN NOT MATCHED THEN
      INSERT ROW
  WHEN NOT MATCHED BY SOURCE THEN
      DELETE;
  