SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function if (children 1)
     ExpressionList (children 3)
      Function equals (children 1)
       ExpressionList (children 2)
        Function length (children 1)
         ExpressionList (children 1)
          Function topK (children 2)
           ExpressionList (children 1)
            Function length (children 1)
             ExpressionList (children 1)
              Identifier merged_from
           ExpressionList (children 1)
            Literal UInt64_2
        Literal UInt64_2
      Function lessOrEquals (children 1)
       ExpressionList (children 2)
        Function arrayMin (children 1)
         ExpressionList (children 1)
          Function topK (children 2)
           ExpressionList (children 1)
            Function length (children 1)
             ExpressionList (children 1)
              Identifier merged_from
           ExpressionList (children 1)
            Literal UInt64_2
        Literal UInt64_3
      Literal UInt64_1
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier system.part_log
   Function and (children 1)
    ExpressionList (children 3)
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier table
       Literal \'limited_merge_table\'
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier database
       Function currentDatabase (children 1)
        ExpressionList
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier event_type
       Literal \'MergeParts\'
