org.rocksdb.util

Class ReverseBytewiseComparator

java.lang.Object

org.rocksdb.AbstractNativeReference

org.rocksdb.AbstractImmutableNativeReference

org.rocksdb.RocksCallbackObject

org.rocksdb.AbstractComparator

org.rocksdb.util.ReverseBytewiseComparator

All Implemented Interfaces:

AutoCloseable

public final class ReverseBytewiseComparator
extends AbstractComparator

This is a Java Native implementation of the C++ equivalent ReverseBytewiseComparatorImpl using Slice The performance of Comparators implemented in Java is always less than their C++ counterparts due to the bridging overhead, as such you likely don't want to use this apart from benchmarking and you most likely instead wanted BuiltinComparator.REVERSE_BYTEWISE_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
ReverseBytewiseComparator(ComparatorOptions copt)

Method Summary

Modifier and Type	Method and Description
int	compare(ByteBuffer a, ByteBuffer b) Three-way key comparison.
void	findShortestSeparator(ByteBuffer start, ByteBuffer limit) 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

findShortSuccessor, initializeNative, usingDirectBuffers

Methods inherited from class org.rocksdb.RocksCallbackObject

disposeInternal

Methods inherited from class org.rocksdb.AbstractImmutableNativeReference

close, disOwnNativeHandle, isOwningHandle

Methods inherited from class org.rocksdb.AbstractNativeReference

dispose, finalize

Methods inherited from class java.lang.Object

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

Constructor Detail

ReverseBytewiseComparator

public ReverseBytewiseComparator(ComparatorOptions copt)

Method Detail

name

public 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 int compare(ByteBuffer a,
                   ByteBuffer b)

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:

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

b - 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 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