text: ALTER TABLE jobs DROP COLUMN nominal_time;
  ALTER TABLE jobs ALTER COLUMN description DROP NOT NULL;
  ALTER TABLE jobs ADD COLUMN current_owner_name VARCHAR(64);
  
  ALTER TABLE job_versions ADD COLUMN version UUID;
  ALTER TABLE job_versions ADD COLUMN uri VARCHAR(256);
  ALTER TABLE job_versions DROP COLUMN git_repo_uri;
  ALTER TABLE job_versions DROP COLUMN git_sha;
  ALTER TABLE job_versions ALTER COLUMN input_dataset DROP NOT NULL;
  ALTER TABLE job_versions ALTER COLUMN output_dataset DROP NOT NULL;
  
  CREATE TABLE IF NOT EXISTS job_run_definitions (
      guid UUID PRIMARY KEY,
      job_version_guid UUID REFERENCES job_versions(guid),
      run_args_json TEXT,
      content_hash UUID NOT NULL,
      nominal_start_time INTEGER,
      nominal_end_time INTEGER,
      created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
  );
  
  