Subject: AvroStorage taking long time to load and iterate over records

I am noticing weird behavior where loading and iterating avro records via AvroStorage takes long time as compared to  iterating via MapReduce job.  Any known issues or any clue as to why AvroStorage would take such long time ?
Example:Schema which I am using:
{  "type": "record",  "name": "Timber",  "namespace": "com.timber.avro",  "fields": [    {      "name": "identifier",      "type": "string",      "doc": "Identifier. NonNull."    },    {      "name": "reservation",      "type": [        "null",        {          "type": "array",          "items": {            "name": "Reservation",            "type": "record",            "fields": [              {                "name": "bookingDate",                "type": "long",                "doc": "Timestamp in UTC. NonNull"              },              {                "name": "code",                "type": [                  "null",                  "string"                ],                "doc": "Code.",                "default": null              },                          ]          }        }      ],      "default": null,      "doc": "array of segment id which this urn belongs."    }  ]}
using Pig AvroStorage, it takes more than 30 minutes to simple iterate. I have been adding more optional fields (like code) in above Reservation record. Does that affect how I am using AvroStorage ?
register /json-simple-1.1.jarregister /piggybank.jar
records = LOAD '/data/*/one.avro'          USING'no_schema_check')
reservation = FOREACH records {            selectHotelAtt = FOREACH reservation GENERATE bookingDate;            GENERATE FLATTEN(selectHotelAtt.bookingDate) as bookingDate;                };DUMP reservation;

Mapper interface        @Override        public void map(final AvroKey<Timber> key, final NullWritable value, final Context context) throws IOException, InterruptedException {