Package org.rocksdb

Interface RocksIteratorInterface

All Known Implementing Classes:
AbstractRocksIterator, RocksIterator, SstFileReaderIterator, WBWIRocksIterator
public interface RocksIteratorInterface

Defines the interface for an Iterator which provides access to data one entry at a time. Multiple implementations are provided by this library. In particular, iterators are provided to access the contents of a DB and Write Batch.

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:

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    isValid()
    An iterator is either positioned at an entry, or not valid.
    void
    next()
    Moves to the next entry in the source.
    void
    prev()
    Moves to the previous entry in the source.
    void
    refresh()
    If supported, the DB state that the iterator reads from is updated to the latest state.
    void
    refresh(Snapshot snapshot)
    Similar to refresh() but the iterator will be reading the latest DB state under the given snapshot.
    void
    seek(byte[] target)
    Position at the first entry in the source whose key is at or past target.
    void
    seek(ByteBuffer target)
    Position at the first entry in the source whose key is that or past target.
    void
    seekForPrev(byte[] target)
    Position at the first entry in the source whose key is that or before target.
    void
    seekForPrev(ByteBuffer target)
    Position at the last key that is less than or equal to the target key.
    void
    seekToFirst()
    Position at the first entry in the source.
    void
    seekToLast()
    Position at the last entry in the source.
    void
    status()
    If an error has occurred, return it.

  • Method Details

    • isValid

      boolean isValid()

      An iterator is either positioned at an entry, or not valid. This method returns true if the iterator is valid.

      Returns:
      true if iterator is valid.

    • seekToFirst

      void seekToFirst()

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

    • seekToLast

      void seekToLast()

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

    • seek

      void seek(byte[] target)

      Position at the first entry in the source whose key is at or past target.

      The iterator is valid after this call if the source contains a key that comes at or past target.

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

    • seekForPrev

      void seekForPrev(byte[] target)

      Position at the first entry in the source whose key is that or before target.

      The iterator is valid after this call if the source contains a key that comes at or before target.

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

    • seek

      void seek(ByteBuffer target)

      Position at the first entry in the source whose key is that or past target.

      The iterator is valid after this call if the source contains a key that comes at or past target.

      Parameters:
      target - byte array describing a key or a key prefix to seek for. Supports direct buffer only.

    • seekForPrev

      void seekForPrev(ByteBuffer target)

      Position at the last key that is less than or equal to the target key.

      The iterator is valid after this call if the source contains a key that comes at or past target.

      Parameters:
      target - byte array describing a key or a key prefix to seek for. Supports direct buffer only.

    • next

      void next()

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

      REQUIRES: isValid()

    • prev

      void prev()

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

      REQUIRES: isValid()

    • status

      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.

    • refresh

      void refresh() throws RocksDBException

      If supported, the DB state that the iterator reads from is updated to the latest state. The iterator will be invalidated after the call. Regardless of whether the iterator was created/refreshed previously with or without a snapshot, the iterator will be reading the latest DB state after this call.

      Note that you will need to call a Seek*() function to get the iterator back into a valid state before calling a function that assumes the state is already valid, like Next().

      Throws:
      RocksDBException - thrown if the operation is not supported or an error happens in the underlying native library

    • refresh

      void refresh(Snapshot snapshot) throws RocksDBException
      Similar to refresh() but the iterator will be reading the latest DB state under the given snapshot.
      Throws:
      RocksDBException