code: function  collectFilterColumns(dftTable, filter, col)  {
  	var  isLogical = false;
  	if (filter.op === 'AND' || filter.op === 'and' || filter.op === 'OR' || filter.op === 'or')  {
  		filter.op = filter.op.toLowerCase();
  		isLogical = true;
  	}
  
  	if (isLogical)  {
  		filter.filters.forEach(function(f) {
  			collectFilterColumns(dftTable, f, col);
  		});
  	}
  	else  {
  		var  colName = filter.field || filter.name,
  			 fc = {tbName: dftTable, col: colName, orig: colName},
  			 idx = colName.indexOf('.');
  
  		if (idx > 0)  {
  			fc.tbName = colName.substring(0, idx);
  			fc.col = colName.substring(idx+1);
  		}
  
  		if (_.findIndex(col, fc) < 0)
  			col.push(fc);
  	}
  }
docs: Check if a filter contains json-columns