Package org.apache.drill.exec.store.mock

Class ExtendedMockBatchReader

java.lang.Object
org.apache.drill.exec.store.mock.ExtendedMockBatchReader
All Implemented Interfaces:
ManagedReader<SchemaNegotiator>
public class ExtendedMockBatchReader extends Object implements ManagedReader<SchemaNegotiator>
Extended form of the mock record reader that uses generator class instances to create the mock values. This is a work in progress. Generators exist for a few simple required types. One also exists to generate strings that contain dates.

The definition is provided inside the sub scan used to create the ScanBatch used to create this record reader.

  • Constructor Details

  • Method Details

    • open

      public boolean open(SchemaNegotiator schemaNegotiator)
      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<SchemaNegotiator>
      Parameters:
      schemaNegotiator - 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<SchemaNegotiator>
      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<SchemaNegotiator>