Hello,
I have a 340 MB avro data file that contains records sorted and identified
by unique id (duplicate records exists). At the beginning of every unique
record a synchronization point is created with DataFileWriter.sync(). (I
cannot or do not want to save the sync points and i do not want to use
SortedKeyValueFile as output format for M/R job)
There are at-least 25k synchronization points in a 340 MB file.
Ex:
Marker1_RecordA1_RecordA2_RecordA3_Marker2_RecordB1_RecordB2
As records are sorted, for efficient retrieval, binary search is performed
using the attached code.
Most of the times the search is successful, at times the code throws the
following exception
------
org.apache.avro.AvroRuntimeException: java.io.IOException: Invalid sync! at
org.apache.avro.file.DataFileStream.hasNext(DataFileStream.java:210
------
Questions
1) Is it ok to have 25k sycn points for 300 MB file ? Does it cost in
performance while reading ?
2) I note down the position that was used to invoke fileReader.sync(mid);.
If i catch AvroRuntimeException, close and open the file and sync(mid) i do
not see exception. Why should Avro throw exception before and not later ?
3) Is there a limit on number of times sync() is invoked ?
4) When sync(position) is invoked, are any 0 >= position <= file.size()
valid ? If yes why do i see AvroRuntimeException (#2) ?
Regards,
Deepak
fileReader = new DataFileReader<GenericData.Record>(new FsInput(avroFile, conf),
new
SpecificDatumReader<GenericData.Record>());
long high = fileStatus.getLen();
fileReader.sync(0);
long low = fileReader.tell();
while (low < high) {
count--;
long mid = (high + low) >>> 1;
fileReader.sync(mid);
if (fileReader.hasNext()) {
event = (Event)
fileReader.next().get(VALUE);
if
(guidToSearch.compareTo(event.getGuid().toString()) > 0) {
low = mid;
lowModified =
true;
} else if
(guidToSearch.compareTo(event.getGuid().toString()) < 0) {
high = mid;
highModified =
true;
} else {
fileReader.sync(low);
event = (Event)
fileReader.next().get(VALUE);
scan(fileReader, event, guidToSearch, conf, avroFile);
break;
}
} else {
break;
}
