Package com.apple.foundationdb.record.provider.foundationdb.cursors

Class MergeCursorContinuation<B extends Message.Builder,C extends RecordCursorContinuation>

java.lang.Object

com.apple.foundationdb.record.provider.foundationdb.cursors.MergeCursorContinuation<B,C>

Type Parameters:

B - the builder for message type of the continuation proto message

C - type of the continuation

All Implemented Interfaces:

RecordCursorContinuation

@API(INTERNAL)
public abstract class MergeCursorContinuation<B extends Message.Builder,C extends RecordCursorContinuation>
extends Object
implements RecordCursorContinuation

Common code for handling the continuations of MergeCursors. The continuations for these cursors are constructed from a Protobuf message containing information on the state of each child cursor. This class handles caching that Protobuf message and its byte representation so that subsequent calls to get the continuation are fast. It also abstracts away some of the logic for converting a list of continuations into a single Protobuf message, but this is still somewhat clunky because Protobuf does not support Message inheritance (which limits the opportunity for polymorphism).

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	MergeCursorContinuation(List<C> continuations, Message originalProto)

Method Summary

Modifier and Type	Method	Description
protected abstract void	addOtherChild(B builder, C continuation)	Fill in the Protobuf builder with the information for a child other than the first or second child.
protected List<C>	getContinuations()
protected abstract B	newProtoBuilder()	Get a new builder instance for the Protobuf message associated with this continuation.
protected abstract void	setFirstChild(B builder, C continuation)	Fill in the Protobuf builder with the information from the first child.
protected abstract void	setSecondChild(B builder, C continuation)	Fill in the Protobuf builder with the information from the second child.
byte[]	toBytes()	Serialize this continuation to a byte array.
protected Message	toProto()

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.apple.foundationdb.record.RecordCursorContinuation

isEnd

Constructor Detail

MergeCursorContinuation

protected MergeCursorContinuation(@Nonnull
                                  List<C> continuations,
                                  @Nullable
                                  Message originalProto)

Method Detail

setFirstChild

protected abstract void setFirstChild(@Nonnull
                                      B builder,
                                      @Nonnull
                                      C continuation)

Fill in the Protobuf builder with the information from the first child. For backwards-compatibility reasons, cursors may handle this differently than the other children. This method will be called before setSecondChild(B, C) and all calls to addOtherChild(B, C).

Parameters:

builder - a builder for the Protobuf continuation

continuation - the first child's continuation

setSecondChild

protected abstract void setSecondChild(@Nonnull
                                       B builder,
                                       @Nonnull
                                       C continuation)

Fill in the Protobuf builder with the information from the second child. For backwards-compatibility reasons, cursors may handle this differently than the other children. This method will be called after setFirstChild(B, C) and before all calls to addOtherChild(B, C).

Parameters:

builder - a builder for the Protobuf continuation

continuation - the second child's continuation

addOtherChild

protected abstract void addOtherChild(@Nonnull
                                      B builder,
                                      @Nonnull
                                      C continuation)

Fill in the Protobuf builder with the information for a child other than the first or second child. For backwards-compatibility reasons, cursors may handle those two children differently than the other children. This method will be called in the same order as the continuations in getContinuations().

Parameters:

builder - a builder for the Protobuf continuation

continuation - a child other than the first or second child

newProtoBuilder

@Nonnull
protected abstract B newProtoBuilder()

Get a new builder instance for the Protobuf message associated with this continuation. This should typically be implemented by calling the newBuilder() method on the appropriate message type.

Returns:

a new builder for the underlying Protobuf message type

toProto

@Nonnull
protected Message toProto()

toBytes

@Nullable
public byte[] toBytes()

Description copied from interface: RecordCursorContinuation

Serialize this continuation to a byte array. This method must always return the same array contents (but not necessarily the same array). If RecordCursorContinuation.isEnd() returns true, then toBytes() must return null.

Specified by:

toBytes in interface RecordCursorContinuation

Returns:

a (possibly null) byte array containing a binary serialization of this continuation

getContinuations

@Nonnull
protected List<C> getContinuations()