Explain EXPLAIN (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Identifier arr
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier index_test
    Function has (children 1)
     ExpressionList (children 2)
      Function arrayMap (children 1)
       ExpressionList (children 3)
        Function lambda (children 1)
         ExpressionList (children 2)
          Function tuple (children 1)
           ExpressionList (children 2)
            Identifier x
            Identifier y
          Function concat (children 1)
           ExpressionList (children 2)
            Function lower (children 1)
             ExpressionList (children 1)
              Identifier x
            Identifier y
        Identifier arr
        Identifier arr
      Literal \'a_12A_12\'
    Set
