[C++][Java] Handle Arrow stream with zero record batch

[asfimport]

It looks like currently many places of the code assume that there needs to be at least one record batch for streaming format. Is zero-recordbatch not supported by design?

e.g. https://github.com/apache/arrow/blob/master/java/tools/src/main/java/org/apache/arrow/tools/StreamToFile.java#L45

  public static void convert(InputStream in, OutputStream out) throws IOException {
    BufferAllocator allocator = new RootAllocator(Integer.MAX_VALUE);
    try (ArrowStreamReader reader = new ArrowStreamReader(in, allocator)) {
      VectorSchemaRoot root = reader.getVectorSchemaRoot();
      // load the first batch before instantiating the writer so that we have any dictionaries
      if (!reader.loadNextBatch()) {
        throw new IOException("Unable to read first record batch");
      }
      ...

Pyarrow-0.8.0 does not load 0-recordbatch stream either. It would throw an exception originated from https://github.com/apache/arrow/blob/a95465b8ce7a32feeaae3e13d0a64102ffa590d9/cpp/src/arrow/table.cc#L309:

Status Table::FromRecordBatches(const std::vector<std::shared_ptr<RecordBatch>>& batches,
                                std::shared_ptr<Table>* table) {
  if (batches.size() == 0) {
    return Status::Invalid("Must pass at least one record batch");
  }
  ...

Reporter: Jingyuan Wang / @alphalfalfa
Assignee: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #3871

_{Note: This issue was originally created as ARROW-2119. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
I believe we should make some changes to support streams having a schema but no record batches. In C++ / Python, if there are none, then Table::FromRecordBatches should not be called

[asfimport]

Wes McKinney / @wesm:
I think this might be fixed. I added it to 0.13 to check C++ at least

[asfimport]

Wes McKinney / @wesm:
This can be resolved by adding a zero-record-batch stream to the integration tests

[asfimport]

Wes McKinney / @wesm:
The patch I put up is full of failures. I'm doubtful this can be resolved in time for 0.13

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 3871
#3871