Package org.apache.beam.sdk.schemas.utils

Class SelectHelpers

  • @Experimental(SCHEMAS)
public class SelectHelpers
extends java.lang.Object
    Helper methods to select subrows out of rows.

    • Field Detail

      • CONCAT_FIELD_NAMES

        public static final SerializableFunction<java.util.List<java.lang.String>,​java.lang.String> CONCAT_FIELD_NAMES
        This policy keeps all levels of a name. Every field name in the path to a given field is concated with _ characters.

      • KEEP_NESTED_NAME

        public static final SerializableFunction<java.util.List<java.lang.String>,​java.lang.String> KEEP_NESTED_NAME
        This policy keeps the raw nested field name. If two differently-nested fields have the same name, flattening will fail with this policy.

    • Constructor Detail

      • SelectHelpers

        public SelectHelpers()

    • Method Detail

      • getOutputSchema

        public static Schema getOutputSchema​(Schema inputSchema,
                                     FieldAccessDescriptor fieldAccessDescriptor)
        Get the output schema resulting from selecting the given FieldAccessDescriptor from the given schema.

        Fields are always extracted and then stored in a new Row. For example, consider the following Java POJOs: 

        
  class UserEvent {
    String userId;
    String eventId;
    int eventType;
    Location location;
 }
 
        
 class Location {
   double latitude;
   double longitude;
 }

        If selecting just the location field, then the returned schema will wrap that of the singular field being selected; in this case the returned schema will be a Row containing a single Location field. If location.latitude is selected, then the returned Schema will be a Row containing a double latitude field.

        The same holds true when selecting from lists or maps. For example: 

        
 class EventList {
   List<UserEvent> events;
 }

        If selecting events.location.latitude, the returned schema will contain a single array of Row, where that Row contains a single double latitude field; it will not contain an array of double.