how to alter table drop a column in array type column

[Ekin]

Dear all


       Plean help，  I have a table like :
       
       table tour ( id string,  points array<struct<lon double,lat double, 
direction double>> )
       
        when i want to drop column direction in points, i get an error like 
this( in spark sql):
     
    spark.sql("  alter table tour drop column points.direction").show



org.apache.spark.sql.AnalysisException: Field name points. direction is 
invalid: points is not a struct.; line 1 pos 0

  at 
org.apache.spark.sql.errors.QueryCompilationErrors$.invalidFieldName(QueryCompilationErrors.scala:2368)

  at org.apache.spark.sql.types.StructType.findField$1(StructType.scala:359)

  at org.apache.spark.sql.types.StructType.findNestedField(StructType.scala:384)










   how can i to drop this column in array<struct> type column ?   thank you 
very much!