Package org.apache.druid.frame.file

Class FrameFileWriter

java.lang.Object

org.apache.druid.frame.file.FrameFileWriter

All Implemented Interfaces:

Closeable, AutoCloseable

public class FrameFileWriter
extends Object
implements Closeable

Writer for FrameFile. See that class for format information.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	CHECKSUM_SEED
static final byte[]	MAGIC
static final byte	MARKER_FRAME
static final byte	MARKER_NO_MORE_FRAMES
static final byte	MARKER_RAC
static final int	NO_PARTITION
static final int	TRAILER_LENGTH

Method Summary

Modifier and Type	Method	Description
void	abort()	Stops writing this file and closes early.
void	close()
static FrameFileWriter	open(WritableByteChannel channel, ByteBuffer compressionBuffer, ByteTracker byteTracker, WireTransferableContext wireTransferableContext)	Opens a writer for a particular channel.
void	write(RowsAndColumns rac, int partition)	Write a batch of data to the file.

Methods inherited from class java.lang.Object

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

Field Details

MAGIC

public static final byte[] MAGIC

MARKER_FRAME

public static final byte MARKER_FRAME

See Also:

• Constant Field Values

MARKER_NO_MORE_FRAMES

public static final byte MARKER_NO_MORE_FRAMES

See Also:

• Constant Field Values

MARKER_RAC

public static final byte MARKER_RAC

See Also:

• Constant Field Values

TRAILER_LENGTH

public static final int TRAILER_LENGTH

See Also:

• Constant Field Values

CHECKSUM_SEED

public static final int CHECKSUM_SEED

See Also:

• Constant Field Values

NO_PARTITION

public static final int NO_PARTITION

See Also:

• Constant Field Values

Method Details

open

public static FrameFileWriter open(WritableByteChannel channel,
 @Nullable
 ByteBuffer compressionBuffer,
 ByteTracker byteTracker,
 WireTransferableContext wireTransferableContext)

Opens a writer for a particular channel.

Parameters:

channel - destination channel

compressionBuffer - result of Frame.compressionBufferSize(long) for the largest possible frame size that will be written to this file, or null to allocate buffers dynamically. Providing an explicit buffer here, if possible, improves performance.

byteTracker - tracker to limit the number of bytes that can be written to the frame file

wireTransferableContext - context for wire transfer serialization

write

public void write(RowsAndColumns rac,
 int partition)
           throws IOException

Write a batch of data to the file. If legacy frame serialization is enabled and the RowsAndColumns can be converted to a Frame, it will be written as raw frame bytes with MARKER_FRAME. Otherwise, it will be written using WireTransferable with MARKER_RAC.

Parameters:

rac - the RowsAndColumns to write

partition - partition number for a partitioned frame file, or NO_PARTITION for an unpartitioned file. Must be monotonically increasing.

Throws:

IOException

abort

public void abort()
           throws IOException

Stops writing this file and closes early. Readers will be able to detect that the file is truncated due to the lack of MARKER_NO_MORE_FRAMES. After calling this method, close() does nothing.

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException