Package org.apache.drill.exec.store.hdf5

Class HDF5BatchReader

java.lang.Object
org.apache.drill.exec.store.hdf5.HDF5BatchReader
All Implemented Interfaces:
ManagedReader<FileScanFramework.FileSchemaNegotiator>
public class HDF5BatchReader extends Object implements ManagedReader<FileScanFramework.FileSchemaNegotiator>

  • Constructor Details

  • Method Details

    • open

      public boolean open(FileScanFramework.FileSchemaNegotiator negotiator)
      Description copied from interface: ManagedReader
      Setup the record reader. Called just before the first call to next(). Allocate resources here, not in the constructor. Example: open files, allocate buffers, etc.
      Specified by:
      open in interface ManagedReader<FileScanFramework.FileSchemaNegotiator>
      Parameters:
      negotiator - mechanism to negotiate select and table schemas, then create the row set reader used to load data into value vectors
      Returns:
      true if the reader is open and ready to read (possibly no) rows. false for a "soft" failure in which no schema or data is available, but the scanner should not fail, it should move onto another reader

    • next

      public boolean next()
      Description copied from interface: ManagedReader
      Read the next batch. Reading continues until either EOF, or until the mutator indicates that the batch is full. The batch is considered valid if it is non-empty. Returning true with an empty batch is valid, and is helpful on the very first batch (returning schema only.) An empty batch with a false return code indicates EOF and the batch will be discarded. A non-empty batch along with a false return result indicates a final, valid batch, but that EOF was reached and no more data is available.

      This somewhat complex protocol avoids the need to allocate a final batch just to find out that no more data is available; it allows EOF to be returned along with the final batch.

      Specified by:
      next in interface ManagedReader<FileScanFramework.FileSchemaNegotiator>
      Returns:
      true if more data may be available (and so next() should be called again, false to indicate that EOF was reached

    • close

      public void close()
      Description copied from interface: ManagedReader
      Release resources. Called just after a failure, when the scanner is cancelled, or after next() returns EOF. Release all resources and close files. Guaranteed to be called if open() returns normally; will not be called if open() throws an exception.
      Specified by:
      close in interface ManagedReader<FileScanFramework.FileSchemaNegotiator>