SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Asterisk
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Function explain_index_has (children 1)
       ExpressionList (children 2)
        Function equals (children 1)
         ExpressionList (children 2)
          Identifier use_idx_fixed
          Literal UInt64_1
        Function equals (children 1)
         ExpressionList (children 2)
          Identifier filter
          Function toFixedString (children 1)
           ExpressionList (children 2)
            Literal \'K3\'
            Literal UInt64_2
