code: private boolean isHashKey(TableKraken table,
                              ColumnExpr columnExpr)
    {
      String keyName = ":key_" + columnExpr.getColumn().name();
      
      Column keyColumn = table.getColumn(keyName);
      
      return (keyColumn != null && isKey(table, keyColumn));
    }
docs: /*
  @Override
  public ExprKraken bindKey(QueryBuilderKraken builder)
  {
  if (_op != BinaryOp.EQ) {
  return null;
  }
  
  if (_left instanceof ColumnExpr) {
  ColumnExpr left = (ColumnExpr) _left;
  
  if (isKey(builder.getTable(), left)) {
  return new PodKeyExpr(left.getColumn(), _right);
  }
  }
  
  if (_right instanceof ColumnExpr) {
  ColumnExpr right = (ColumnExpr) _right;
  
  if (isKey(builder.getTable(), right)) {
  return new PodKeyExpr(right.getColumn(), _left);
  }
  }
  
  return null;
  }