Package org.rocksdb

Class AbstractComparator

    • Constructor Detail

    • Method Detail

      • initializeNative

        protected long initializeNative​(long... nativeParameterHandles)
        Description copied from class: RocksCallbackObject
        Construct the Native C++ object which will callback to our object methods
        Specified by:
        initializeNative in class RocksCallbackObject
        Parameters:
        nativeParameterHandles - An array of native handles for any parameter objects that are needed during construction
        Returns:
        The native handle of the C++ object which will callback to us

      • name

        public abstract java.lang.String name()
        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.
        Returns:
        The name of this comparator implementation

      • compare

        public abstract int compare​(java.nio.ByteBuffer a,
                            java.nio.ByteBuffer b)
        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.
        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​(java.nio.ByteBuffer start,
                                  java.nio.ByteBuffer limit)

        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.

        Parameters:
        start - the start
        limit - the limit

      • findShortSuccessor

        public void findShortSuccessor​(java.nio.ByteBuffer key)

        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.

        Parameters:
        key - the key

      • usingDirectBuffers

        public final boolean usingDirectBuffers()