[jira] [Created] (AVRO-2280) Calling DataFileWriter::flush() when there is no data to write can subsequently cause an exception when the file is read

["Brian Walshe (JIRA)" <ji...@apache.org>]

Brian Walshe created AVRO-2280:
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             Summary: Calling DataFileWriter::flush() when there is no data to write can subsequently cause an exception when the file is read
                 Key: AVRO-2280
                 URL: https://issues.apache.org/jira/browse/AVRO-2280
             Project: Apache Avro
          Issue Type: Bug
          Components: c++
            Reporter: Brian Walshe


If you call flush() on a DataFileWriter object that has no data waiting to be written, this will produce an empty block at the end of the file which will cause an exception on the last call to DataFileReader::read(T& datum)
h2. Example

For example adding the following to the Data File unit tests will cause them to break [https://github.com/bwalshe/avro/blob/7c6a229b2fcbb0b88368e1503a58daef9f43ee64/lang/c%2B%2B/test/DataFileTests.cc#L192]
h2. Possible Solution

Altering DataFileWriter::sync() to check if there are objects to be written before proceeding will get the code to pass the unit tests. e.g.: [https://github.com/bwalshe/avro/blob/7c6a229b2fcbb0b88368e1503a58daef9f43ee64/lang/c%2B%2B/impl/DataFile.cc#L141 |https://github.com/bwalshe/avro/blob/7c6a229b2fcbb0b88368e1503a58daef9f43ee64/lang/c%2B%2B/impl/DataFile.cc#L141]

 



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