leveldb-api(1)：DB.java

github地址：leveldb/leveldb-api/src/main/java/org/iq80/leveldb at master · dain/leveldb · GitHub

DB.java

DB类接口实现：继承了Closeable接口

public interface DB
        extends Iterable<Map.Entry<byte[], byte[]>>, Closeable

迭代器DBIterator：用于遍历

    DBIterator iterator();

    DBIterator iterator(ReadOptions options);

三种方法：put  delete  write

   void put(byte[] key, byte[] value)
            throws DBException;

    void delete(byte[] key)
            throws DBException;

    void write(WriteBatch updates)
            throws DBException;

批量写数据：

 WriteBatch createWriteBatch();

put操作后返回snapshot：

    /**
     * @return null if options.isSnapshot()==false otherwise returns a snapshot
     * of the DB after this operation.
     */
    Snapshot put(byte[] key, byte[] value, WriteOptions options)
            throws DBException;

delete操作后返回snapshot：

    /**
     * @return null if options.isSnapshot()==false otherwise returns a snapshot
     * of the DB after this operation.
     */
    Snapshot delete(byte[] key, WriteOptions options)
            throws DBException;

write操作后返回snapshot：

    /**
     * @return null if options.isSnapshot()==false otherwise returns a snapshot
     * of the DB after this operation.
     */
    Snapshot write(WriteBatch updates, WriteOptions options)
            throws DBException;

快照：

 Snapshot getSnapshot();

getApproximateSize方法可以用于获取一个或多个key range占用的文件系统空间的近似大小：

long[] getApproximateSizes(Range... ranges);

getProperty方法获取系统属性

String getProperty(String name);

suspend 后台compaction：

    /**
     * Suspends any background compaction threads.  This methods
     * returns once the background compactions are suspended.
     */
    void suspendCompactions()
            throws InterruptedException;

resume后台compaction：

    /**
     * Resumes the background compaction threads.
     */
    void resumeCompactions();

指定compaction的范围：

    /**
     * Force a compaction of the specified key range.
     *
     * @param begin if null then compaction start from the first key
     * @param end if null then compaction ends at the last key
     */
    void compactRange(byte[] begin, byte[] end)
            throws DBException;