org.rocksdb

Class RocksIterator

java.lang.Object

org.rocksdb.RocksObject

org.rocksdb.RocksIterator

public class RocksIterator
extends RocksObject

An iterator yields a sequence of key/value pairs from a source. The following class defines the interface. Multiple implementations are provided by this library. In particular, iterators are provided to access the contents of a Table or a DB.

Multiple threads can invoke const methods on an RocksIterator without external synchronization, but if any of the threads may call a non-const method, all threads accessing the same RocksIterator must use external synchronization.

See Also:

RocksObject

Field Summary

Fields inherited from class org.rocksdb.RocksObject

nativeHandle_

Constructor Summary

Constructors

Constructor and Description
RocksIterator(RocksDB rocksDB, long nativeHandle)

Method Summary

Modifier and Type	Method and Description
protected void	disposeInternal() Deletes underlying C++ iterator pointer.
boolean	isValid() An iterator is either positioned at a key/value pair, or not valid.
byte[]	key() Return the key for the current entry.
void	next() Moves to the next entry in the source.
void	prev() Moves to the previous entry in the source.
void	seek(byte[] target) Position at the first key in the source that at or past target The iterator is valid after this call iff the source contains an entry that comes at or past target.
void	seekToFirst() Position at the first key in the source.
void	seekToLast() Position at the last key in the source.
void	status() If an error has occurred, return it.
byte[]	value() Return the value for the current entry.

Methods inherited from class org.rocksdb.RocksObject

disOwnNativeHandle, dispose, finalize, isInitialized, isOwningNativeHandle

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RocksIterator

public RocksIterator(RocksDB rocksDB,
                     long nativeHandle)

Method Detail

isValid

public boolean isValid()

An iterator is either positioned at a key/value pair, or not valid. This method returns true iff the iterator is valid.

Returns:

true if iterator is valid.

seekToFirst

public void seekToFirst()

Position at the first key in the source. The iterator is Valid() after this call iff the source is not empty.

seekToLast

public void seekToLast()

Position at the last key in the source. The iterator is valid after this call iff the source is not empty.

next

public void next()

Moves to the next entry in the source. After this call, Valid() is true iff the iterator was not positioned at the last entry in the source.

REQUIRES: isValid()

prev

public void prev()

Moves to the previous entry in the source. After this call, Valid() is true iff the iterator was not positioned at the first entry in source.

REQUIRES: isValid()

key

public byte[] key()

Return the key for the current entry. The underlying storage for the returned slice is valid only until the next modification of the iterator.

REQUIRES: isValid()

Returns:

key for the current entry.

value

public byte[] value()

Return the value for the current entry. The underlying storage for the returned slice is valid only until the next modification of the iterator.

REQUIRES: !AtEnd() && !AtStart()

Returns:

value for the current entry.

seek

public void seek(byte[] target)

Position at the first key in the source that at or past target The iterator is valid after this call iff the source contains an entry that comes at or past target.

Parameters:

target - byte array describing a key or a key prefix to seek for.

status

public void status()
            throws RocksDBException

If an error has occurred, return it. Else return an ok status. If non-blocking IO is requested and this operation cannot be satisfied without doing some IO, then this returns Status::Incomplete().

Throws:

RocksDBException - thrown if error happens in underlying native library.

disposeInternal

protected void disposeInternal()

Deletes underlying C++ iterator pointer.

Note: the underlying handle can only be safely deleted if the RocksDB instance related to a certain RocksIterator is still valid and initialized. Therefore disposeInternal() checks if the RocksDB is initialized before freeing the native handle.

Specified by:

disposeInternal in class RocksObject