org.apache.drill.exec.physical.impl.scan.v3

Class BaseScanTest.EofOnOpenReader

java.lang.Object

org.apache.drill.exec.physical.impl.scan.v3.BaseScanTest.EofOnOpenReader

All Implemented Interfaces:

ManagedReader

Enclosing class:

BaseScanTest

protected static class BaseScanTest.EofOnOpenReader
extends Object
implements ManagedReader

Mock reader that returns no schema and no records.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.drill.exec.physical.impl.scan.v3.ManagedReader

ManagedReader.EarlyEofException

Constructor Summary

Constructors

Constructor and Description
EofOnOpenReader(SchemaNegotiator schemaNegotiator)

Method Summary

Modifier and Type	Method and Description
void	close() Release resources.
boolean	next() Read the next batch.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EofOnOpenReader

public EofOnOpenReader(SchemaNegotiator schemaNegotiator)
                throws ManagedReader.EarlyEofException

Throws:

ManagedReader.EarlyEofException

Method Detail

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

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