SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function lessOrEquals (children 1)
     ExpressionList (children 2)
      Function avg (children 1)
       ExpressionList (children 1)
        Function blockSize (children 1)
         ExpressionList
      Literal UInt64_10000
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier system.columns
   Set
