text: -- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  -- ALWAYS BACKUP YOUR DATA BEFORE EXECUTING THIS SCRIPT
  -- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  
  # This script upgrade DB schema from version 3 to version 4
  
  ALTER TABLE environs DROP COLUMN project_id;
  ALTER TABLE environs ADD COLUMN external_id CHAR(36);
  
  -- make sure to update the schema version to 4
  UPDATE schema_versions SET version=4;
  