org.rocksdb

Class NativeComparatorWrapper

java.lang.Object

org.rocksdb.AbstractNativeReference

org.rocksdb.AbstractImmutableNativeReference

org.rocksdb.RocksCallbackObject

org.rocksdb.AbstractComparator

org.rocksdb.NativeComparatorWrapper

All Implemented Interfaces:

AutoCloseable

public abstract class NativeComparatorWrapper
extends AbstractComparator

A simple abstraction to allow a Java class to wrap a custom comparator implemented in C++. The native comparator must directly extend rocksdb::Comparator.

Field Summary

Fields inherited from class org.rocksdb.RocksCallbackObject

nativeHandle_

Fields inherited from class org.rocksdb.AbstractImmutableNativeReference

owningHandle_

Constructor Summary

Constructors

Constructor and Description
NativeComparatorWrapper()

Method Summary

Modifier and Type	Method and Description
int	compare(ByteBuffer s1, ByteBuffer s2) Three-way key comparison.
protected void	disposeInternal() We override RocksCallbackObject.disposeInternal() as disposing of a native rocksdb::Comparator extension requires a slightly different approach as it is not really a RocksCallbackObject
void	findShortestSeparator(ByteBuffer start, ByteBuffer limit) Used to reduce the space requirements for internal data structures like index blocks.
void	findShortSuccessor(ByteBuffer key) Used to reduce the space requirements for internal data structures like index blocks.
String	name() The name of the comparator.

Methods inherited from class org.rocksdb.AbstractComparator

initializeNative, usingDirectBuffers

Methods inherited from class org.rocksdb.AbstractImmutableNativeReference

close, disOwnNativeHandle, isOwningHandle

Methods inherited from class java.lang.Object

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

Constructor Detail

NativeComparatorWrapper

public NativeComparatorWrapper()

Method Detail

name

public final String name()

Description copied from class: AbstractComparator

The name of the comparator. Used to check for comparator mismatches (i.e., a DB created with one comparator is accessed using a different comparator). A new name should be used whenever the comparator implementation changes in a way that will cause the relative ordering of any two keys to change. Names starting with "rocksdb." are reserved and should not be used.

Specified by:

name in class AbstractComparator

Returns:

The name of this comparator implementation

compare

public final int compare(ByteBuffer s1,
                         ByteBuffer s2)

Description copied from class: AbstractComparator

Three-way key comparison. Implementations should provide a total order on keys that might be passed to it. The implementation may modify the ByteBuffers passed in, though it would be unconventional to modify the "limit" or any of the underlying bytes. As a callback, RocksJava will ensure that a is a different instance from b.

Specified by:

compare in class AbstractComparator

Parameters:

s1 - buffer containing the first key in its "remaining" elements

s2 - buffer containing the second key in its "remaining" elements

Returns:

Should return either: 1) < 0 if "a" < "b" 2) == 0 if "a" == "b" 3) > 0 if "a" > "b"

findShortestSeparator

public final void findShortestSeparator(ByteBuffer start,
                                        ByteBuffer limit)

Description copied from class: AbstractComparator

Used to reduce the space requirements for internal data structures like index blocks.

If start < limit, you may modify start which is a shorter string in [start, limit).

If you modify start, it is expected that you set the byte buffer so that a subsequent read of start.remaining() bytes from start.position() to start.limit() will obtain the new start value.

Simple comparator implementations may return with start unchanged. i.e., an implementation of this method that does nothing is correct.

Overrides:

findShortestSeparator in class AbstractComparator

Parameters:

start - the start

limit - the limit

findShortSuccessor

public final void findShortSuccessor(ByteBuffer key)

Description copied from class: AbstractComparator

Used to reduce the space requirements for internal data structures like index blocks.

You may change key to a shorter key (key1) where key1 ≥ key.

Simple comparator implementations may return the key unchanged. i.e., an implementation of this method that does nothing is correct.

Overrides:

findShortSuccessor in class AbstractComparator

Parameters:

key - the key

disposeInternal

protected void disposeInternal()

We override RocksCallbackObject.disposeInternal() as disposing of a native rocksdb::Comparator extension requires a slightly different approach as it is not really a RocksCallbackObject

Overrides:

disposeInternal in class RocksCallbackObject