Package org.rocksdb

Class NativeComparatorWrapper

  • All Implemented Interfaces:
    java.lang.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.

    • 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
        Returns:
        The name of this comparator implementation

      • compare

        public final int compare​(java.nio.ByteBuffer s1,
                         java.nio.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​(java.nio.ByteBuffer start,
                                        java.nio.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​(java.nio.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