text: -- @ :		collapsing in-sample clusters to consensus peaks ...
  
  -- backup preclustered_peaks
  DROP TABLE IF EXISTS preclustered_peaks;
  RENAME TABLE ce TO preclustered_peaks;
  UPDATE preclustered_peaks SET pc=nc;
  ALTER TABLE preclustered_peaks ADD INDEX(id);
  ALTER TABLE preclustered_peaks ADD INDEX(nc);
  ALTER TABLE preclustered_peaks ADD INDEX(pc);
  
  -- merge clusters
  CREATE TABLE ce
  SELECT
  	nc as id,
  	1 as nc,
  	1 as pc,
  	AVG(mz) as mz,
  	AVG(rt) as rt,
  	AVG(dt) as dt
  FROM
  	preclustered_peaks
  GROUP BY
  	nc
  ;
  
  -- @ :		clustering consensus peaks ...