com.unister.semweb.drums.api
Class DRUMSReader<Data extends AbstractKVStorable>

java.lang.Object
  com.unister.semweb.drums.api.DRUMSReader<Data>

Type Parameters:

Data - an implementation of AbstractKVStorable, e.g. GeneralStorable

public class DRUMSReader<Data extends AbstractKVStorable>
extends java.lang.Object

This class represents an efficient direct access reader. It holds all files opened for reading. Only use this Reader, when there are no write-operations during reading. All files will be locked. Be careful: Opening all files may cost a lot of memory, because all indices are loaded.

Please use the factory-method DRUMS.getReader() get an instance of this class.

Author:

Martin Nettling

Method Summary

void	closeFiles() Closes all files
java.util.List<Data>	get(byte[]... keys) Takes a list of keys and searches for that in all buckets.
java.util.List<Data>	get(long... keys) Takes a list of keys and searches for that in all buckets.
Data	getNextElement(byte[] key) Returns the element which has exact the key or is the next largest element after this key
Data	getPreviousElement(byte[] key) Returns the element which has exact the key or is the next smallest element after this key
java.util.List<Data>	getRange(byte[] lowerKey, byte[] upperKey) Returns all elements between lowerKey and upperKey this function is still BUGGY.
void	openFiles() Opens all files used by the underlying HashFunction.

Methods inherited from class java.lang.Object

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

Method Detail

openFiles

public void openFiles()
               throws FileLockException,
                      java.io.IOException

Opens all files used by the underlying HashFunction. The pointers are stored in files.

Throws:

FileLockException

java.io.IOException

getRange

public java.util.List<Data> getRange(byte[] lowerKey,
                                     byte[] upperKey)
                                                         throws java.io.IOException

Returns all elements between lowerKey and upperKey this function is still BUGGY.

TODO: fix this function. @Nils Why is this function buggy?

Parameters:

lowerKey -

upperKey -

Returns:

a list containing all elements between lowerKey and upperKey

Throws:

java.io.IOException

getPreviousElement

public Data getPreviousElement(byte[] key)
                                                   throws java.io.IOException

Returns the element which has exact the key or is the next smallest element after this key

Parameters:

key -

Returns:

the first element, which can be found before the given key

Throws:

java.io.IOException

getNextElement

public Data getNextElement(byte[] key)
                                               throws java.io.IOException

Returns the element which has exact the key or is the next largest element after this key

Parameters:

key -

Returns:

the first element, which can be found after the given key

Throws:

java.io.IOException

get

public java.util.List<Data> get(long... keys)
                                                    throws DRUMSException,
                                                           java.io.IOException

Takes a list of keys and searches for that in all buckets.

Parameters:

keys -

Returns:

ArrayList

Throws:

DRUMSException

java.io.IOException

get

public java.util.List<Data> get(byte[]... keys)
                                                    throws DRUMSException,
                                                           java.io.IOException

Takes a list of keys and searches for that in all buckets.

Parameters:

keys -

Returns:

ArrayList

Throws:

DRUMSException

java.io.IOException

closeFiles

public void closeFiles()

Closes all files