_quantificationMethod: function (functionName, nslots, column, distinct, callback, error) {
    var tmpl = _.template('select unnest(<%= functionName %>(array_agg(<%= simplify_fn %>((<%= column %>::numeric))), <%= slots %>)) as buckets from (<%= sql %>) _table_sql where <%= column %> is not null');
    this._sqlQuery(tmpl({
      slots: nslots,
      sql: this.getSQL(),