Chengxin Ma created ARROW-7522:
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Summary: Broken Record Batch returned from a function call
Key: ARROW-7522
URL: https://issues.apache.org/jira/browse/ARROW-7522
Project: Apache Arrow
Issue Type: Bug
Components: C++, C++ - Plasma
Affects Versions: 0.15.1
Environment: macOS
Reporter: Chengxin Ma
Scenario: retrieving Record Batch from Plasma with known Object ID.
The following code snippet works well:
{code:java}
int main(int argc, char **argv)
{
plasma::ObjectID object_id =
plasma::ObjectID::from_binary("0FF1CE00C0FFEE00BEEF");
// Start up and connect a Plasma client.
plasma::PlasmaClient client;
ARROW_CHECK_OK(client.Connect("/tmp/store"));
plasma::ObjectBuffer object_buffer;
ARROW_CHECK_OK(client.Get(&object_id, 1, -1, &object_buffer));
// Retrieve object data.
auto buffer = object_buffer.data;
arrow::io::BufferReader buffer_reader(buffer);
std::shared_ptr<arrow::ipc::RecordBatchReader> record_batch_stream_reader;
ARROW_CHECK_OK(arrow::ipc::RecordBatchStreamReader::Open(&buffer_reader,
&record_batch_stream_reader));
std::shared_ptr<arrow::RecordBatch> record_batch;
arrow::Status status = record_batch_stream_reader->ReadNext(&record_batch);
std::cout << "record_batch->column_name(0): " <<
record_batch->column_name(0) << std::endl;
std::cout << "record_batch->num_columns(): " << record_batch->num_columns()
<< std::endl;
std::cout << "record_batch->num_rows(): " << record_batch->num_rows() <<
std::endl;
std::cout << "record_batch->column(0)->length(): "
<< record_batch->column(0)->length() << std::endl;
std::cout << "record_batch->column(0)->ToString(): "
<< record_batch->column(0)->ToString() << std::endl;
}
{code}
{{record_batch->column(0)->ToString()}} would incur a segmentation fault if
retrieving Record Batch is wrapped in a function:
{code:java}
std::shared_ptr<arrow::RecordBatch> GetRecordBatchFromPlasma(plasma::ObjectID
object_id)
{
// Start up and connect a Plasma client.
plasma::PlasmaClient client;
ARROW_CHECK_OK(client.Connect("/tmp/store"));
plasma::ObjectBuffer object_buffer;
ARROW_CHECK_OK(client.Get(&object_id, 1, -1, &object_buffer));
// Retrieve object data.
auto buffer = object_buffer.data;
arrow::io::BufferReader buffer_reader(buffer);
std::shared_ptr<arrow::ipc::RecordBatchReader> record_batch_stream_reader;
ARROW_CHECK_OK(arrow::ipc::RecordBatchStreamReader::Open(&buffer_reader,
&record_batch_stream_reader));
std::shared_ptr<arrow::RecordBatch> record_batch;
arrow::Status status = record_batch_stream_reader->ReadNext(&record_batch);
// Disconnect the client.
ARROW_CHECK_OK(client.Disconnect());
return record_batch;
}
int main(int argc, char **argv)
{
plasma::ObjectID object_id =
plasma::ObjectID::from_binary("0FF1CE00C0FFEE00BEEF");
std::shared_ptr<arrow::RecordBatch> record_batch =
GetRecordBatchFromPlasma(object_id);
std::cout << "record_batch->column_name(0): " <<
record_batch->column_name(0) << std::endl;
std::cout << "record_batch->num_columns(): " << record_batch->num_columns()
<< std::endl;
std::cout << "record_batch->num_rows(): " << record_batch->num_rows() <<
std::endl;
std::cout << "record_batch->column(0)->length(): "
<< record_batch->column(0)->length() << std::endl;
std::cout << "record_batch->column(0)->ToString(): "
<< record_batch->column(0)->ToString() << std::endl;
}
{code}
The meta info of the Record Batch such as number of columns and rows is still
available, but I can't see the content of the columns.
{{lldb}} says that the stop reason is {{EXC_BAD_ACCESS}}, so I think the Record
Batch is destroyed after {{GetRecordBatchFromPlasma}} finishes. But why can I
still see the meta info of this Record Batch?
What is the proper way to get the Record Batch if we insist using a function?
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