org.rocksdb

Class NativeComparatorWrapper

java.lang.Object

org.rocksdb.AbstractNativeReference

org.rocksdb.AbstractImmutableNativeReference

org.rocksdb.RocksCallbackObject

org.rocksdb.AbstractComparator<Slice>

org.rocksdb.NativeComparatorWrapper

All Implemented Interfaces:

java.lang.AutoCloseable

public abstract class NativeComparatorWrapper
extends AbstractComparator<Slice>

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_

Constructor Summary

Constructors

Constructor and Description
NativeComparatorWrapper()

Method Summary

Methods

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

Methods inherited from class org.rocksdb.RocksCallbackObject

initializeNative

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

NativeComparatorWrapper

public NativeComparatorWrapper()

Method Detail

name

public final java.lang.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<Slice>

Returns:

The name of this comparator implementation

compare

public final int compare(Slice s1,
          Slice s2)

Description copied from class: AbstractComparator

Three-way key comparison

Specified by:

compare in class AbstractComparator<Slice>

Parameters:

s1 - Slice access to first key

s2 - Slice access to second key

Returns:

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

findShortestSeparator

public final java.lang.String findShortestSeparator(java.lang.String start,
                                     Slice limit)

Description copied from class: AbstractComparator

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

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

Simple comparator implementations may return null if they wish to use start unchanged. i.e., an implementation of this method that does nothing is correct.

Overrides:

findShortestSeparator in class AbstractComparator<Slice>

Parameters:

start - String

limit - of type T

Returns:

a shorter start, or null

findShortSuccessor

public final java.lang.String findShortSuccessor(java.lang.String key)

Description copied from class: AbstractComparator

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

You may return a new short key (key1) where key1 ≥ key.

Simple comparator implementations may return null if they wish to leave the key unchanged. i.e., an implementation of this method that does nothing is correct.

Overrides:

findShortSuccessor in class AbstractComparator<Slice>

Parameters:

key - String

Returns:

a shorter key, or null

disposeInternal

protected void disposeInternal()

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

Overrides:

disposeInternal in class RocksCallbackObject