SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 4)
   ExpressionList (children 1)
    Function lessOrEquals (children 1)
     ExpressionList (children 2)
      Function avg (children 1)
       ExpressionList (children 1)
        Function blockSize (children 1)
         ExpressionList
      Literal UInt64_10
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier system.tables
   Literal UInt64_10
   Set
