test/org/apache/pig/builtin/avro/schema/recordsSubSchemaNullable.avsc

{
  "name" : "recordsSubSchemaNullable",
  "namespace" : "org.apache.pig.test.builtin",
  "doc" : "subset of records schema, to make sure you can manually specify a compatible subschema",
  "type" : "record",
  "fields" : [
    {"name" : "key", "type" : ["null", "string"]},
    {"name" : "value", "type" : ["null", "string"]}
  ]
}