org.rocksdb.util

Class DirectBytewiseComparator

java.lang.Object

org.rocksdb.AbstractNativeReference

org.rocksdb.AbstractImmutableNativeReference

org.rocksdb.RocksCallbackObject

org.rocksdb.AbstractComparator<DirectSlice>

org.rocksdb.DirectComparator

org.rocksdb.util.DirectBytewiseComparator

All Implemented Interfaces:

java.lang.AutoCloseable

public class DirectBytewiseComparator
extends DirectComparator

This is a Java Native implementation of the C++ equivalent BytewiseComparatorImpl using DirectSlice 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.BYTEWISE_COMPARATOR

Field Summary

Fields inherited from class org.rocksdb.RocksCallbackObject

nativeHandle_

Constructor Summary

Constructors

Constructor and Description
DirectBytewiseComparator(ComparatorOptions copt)

Method Summary

Modifier and Type	Method and Description
int	compare(DirectSlice a, DirectSlice b) Three-way key comparison
java.lang.String	findShortestSeparator(java.lang.String start, DirectSlice 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.DirectComparator

initializeNative

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

DirectBytewiseComparator

public DirectBytewiseComparator(ComparatorOptions copt)

Method Detail

name

public 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<DirectSlice>

Returns:

The name of this comparator implementation

compare

public int compare(DirectSlice a,
                   DirectSlice b)

Description copied from class: AbstractComparator

Three-way key comparison

Specified by:

compare in class AbstractComparator<DirectSlice>

Parameters:

a - Slice access to first key

b - 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 java.lang.String findShortestSeparator(java.lang.String start,
                                              DirectSlice 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<DirectSlice>

Parameters:

start - String

limit - of type T

Returns:

a shorter start, or null

findShortSuccessor

public 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<DirectSlice>

Parameters:

key - String

Returns:

a shorter key, or null