text: -- #slow script#
  UPDATE occurrences SET training=false WHERE training IS NULL;
  UPDATE cache_occurrences_functional SET training=false WHERE training IS NULL;
  
  ALTER TABLE occurrences
     ALTER COLUMN training SET DEFAULT false;
  ALTER TABLE occurrences
     ALTER COLUMN training SET NOT NULL;
  
  ALTER TABLE cache_occurrences_functional
     ALTER COLUMN training SET DEFAULT false;
  ALTER TABLE cache_occurrences_functional
     ALTER COLUMN training SET NOT NULL;
  