Class RAMDirectory

  • All Implemented Interfaces:
    Closeable, Serializable, AutoCloseable

    public class RAMDirectory
    extends Directory
    implements Serializable
    A memory-resident Directory implementation. Locking implementation is by default the SingleInstanceLockFactory but can be changed with Directory.setLockFactory(org.apache.lucene.store.LockFactory).

    Warning: This class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. This class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

    It is recommended to materialize large indexes on disk and use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to Java heap space is not useful.

    See Also:
    Serialized Form
    • Constructor Detail

      • RAMDirectory

        public RAMDirectory()
        Constructs an empty Directory.
      • RAMDirectory

        public RAMDirectory​(Directory dir)
                     throws IOException
        Creates a new RAMDirectory instance from a different Directory implementation. This can be used to load a disk-based index into memory.

        Warning: This class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. This class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

        For disk-based indexes it is recommended to use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to Java heap space is not useful.

        Note that the resulting RAMDirectory instance is fully independent from the original Directory (it is a complete copy). Any subsequent changes to the original Directory will not be visible in the RAMDirectory instance.

        Parameters:
        dir - a Directory value
        Throws:
        IOException - if an error occurs
    • Method Detail

      • listAll

        public final String[] listAll()
        Description copied from class: Directory
        Returns an array of strings, one for each file in the directory.
        Specified by:
        listAll in class Directory
      • fileExists

        public final boolean fileExists​(String name)
        Returns true iff the named file exists in this directory.
        Specified by:
        fileExists in class Directory
      • touchFile

        @Deprecated
        public void touchFile​(String name)
                       throws IOException
        Deprecated.
        Lucene never uses this API; it will be removed in 4.0.
        Set the modified time of an existing file to now.
        Specified by:
        touchFile in class Directory
        Throws:
        IOException - if the file does not exist
      • fileLength

        public final long fileLength​(String name)
                              throws IOException
        Returns the length in bytes of a file in the directory.
        Specified by:
        fileLength in class Directory
        Parameters:
        name - the name of the file for which to return the length.
        Throws:
        IOException - if the file does not exist
      • sizeInBytes

        public final long sizeInBytes()
        Return total size in bytes of all files in this directory. This is currently quantized to RAMOutputStream.BUFFER_SIZE.
      • close

        public void close()
        Closes the store to future operations, releasing associated memory.
        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Specified by:
        close in class Directory