org.hypergraphdb

Class HGStore

java.lang.Object

org.hypergraphdb.HGStore

public class HGStore
extends Object

An instance of HGStore is associated with each HyperGraph to manage to low-level interaction with the underlying database mechanism.

Normally, the HyperGraphDB store is not accessed directly by applications. However, HyperGraphDB type implementors will rely on the HGStore to manage the way raw data is stored and indexed based on a particular type.

Note that a HGStore does not maintain any data cache, nor does it interact in any special way with the semantic layer of HyperGraphDB and the way data and types are laid out in the store.

The HGStore will use the HGStorageImplementation provided by the HGConfiguration parameter to the constructor of this class. In fact, this class is merely a wrapper to the underlying storage implementation.

Author:

Borislav Iordanov

Constructor Summary

Constructors

Constructor and Description
HGStore(String database, HGConfiguration config) Construct a HGStore bound to a specific database location.

Method Summary

Methods

Modifier and Type	Method and Description
void	addIncidenceLink(HGPersistentHandle targetHandle, HGPersistentHandle linkHandle) Update the incidence set of an atom with a newly created link pointing to it.
void	attachOverlayGraph(StorageGraph sgraph) Reserved to internal use.
void	close() Mainly for internal use - invoked by the main HyperGraph instance.
boolean	containsData(HGPersistentHandle handle) Return true if there is a data item bound to the passed in handle parameter and false otherwise.
boolean	containsLink(HGPersistentHandle handle) Return true if there is a storage link bound to the passed in handle parameter and false otherwise.
void	detachOverlayGraph() Reserved to internal use.
<KeyType,ValueType> HGBidirectionalIndex<KeyType,ValueType>	getBidirectionalIndex(String name, ByteArrayConverter<KeyType> keyConverter, ByteArrayConverter<ValueType> valueConverter, Comparator<byte[]> comparator, boolean allowCreate) Retrieve an existing HGBidirectionalIndex by its name.
byte[]	getData(HGPersistentHandle handle) Retrieve the raw data buffer stored at handle.
String	getDatabaseLocation() Return the physical, file system location of the HyperGraph store.
HGRandomAccessResult<HGPersistentHandle>	getIncidenceResultSet(HGPersistentHandle handle) Return a HGSearchResult of atom handles in a given atom's incidence set.
long	getIncidenceSetCardinality(HGPersistentHandle handle) Return the number of atoms in the incidence set of a given atom.
<KeyType,ValueType> HGIndex<KeyType,ValueType>	getIndex(String name) Get the HyperGraphDB index with the given name.
<KeyType,ValueType> HGIndex<KeyType,ValueType>	getIndex(String name, ByteArrayConverter<KeyType> keyConverter, ByteArrayConverter<ValueType> valueConverter, Comparator<byte[]> comparator, boolean allowCreate) Retrieve an HGIndex by its name.
HGPersistentHandle[]	getLink(HGPersistentHandle handle) Retrieve an existing link by its handle.
HGTransactionFactory	getTransactionFactory() Create and return a transaction factory for this HGStore.
HGTransactionManager	getTransactionManager() Return this store's HGTransactionManager.
boolean	hasOverlayGraph() Reserved to internal use.
void	removeData(HGPersistentHandle handle) Remove a raw data value associated with a HGPersistentHandle key.
void	removeIncidenceLink(HGPersistentHandle handle, HGPersistentHandle oldLink) Update the incidence set of an atom by removing a link that no longer points to it.
void	removeIncidenceSet(HGPersistentHandle handle) Remove the whole incidence set of a given handle.
void	removeIndex(String name) Remove an index from the database.
void	removeLink(HGPersistentHandle handle) Remove a link value associated with a HGPersistentHandle key.
HGPersistentHandle	store(byte[] data) Write raw binary data to the store.
HGPersistentHandle	store(HGPersistentHandle[] link) Create a new link in the HyperGraphDB store.
HGPersistentHandle	store(HGPersistentHandle handle, byte[] data) Write raw binary data to the store using a pre-created, unique persistent handle.
HGPersistentHandle	store(HGPersistentHandle handle, HGPersistentHandle[] link) Create a new link in the HyperGraphDB store with an existing handle.

Methods inherited from class java.lang.Object

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

Constructor Detail

HGStore

public HGStore(String database,
       HGConfiguration config)

Construct a HGStore bound to a specific database location.

Parameters:

database -

Method Detail

getTransactionFactory

public HGTransactionFactory getTransactionFactory()

Create and return a transaction factory for this HGStore.

getTransactionManager

public HGTransactionManager getTransactionManager()

Return this store's HGTransactionManager.

getDatabaseLocation

public String getDatabaseLocation()

Return the physical, file system location of the HyperGraph store.

store

public HGPersistentHandle store(HGPersistentHandle[] link)

Create a new link in the HyperGraphDB store. A new HGPersistentHandle is created to refer to the link.

Parameters:

link - A non-null, but possibly empty array of persistent atom handles that constitute the link to be created.

Returns:

The newly created HGPersistentHandle.

store

public HGPersistentHandle store(HGPersistentHandle handle,
                       HGPersistentHandle[] link)

Create a new link in the HyperGraphDB store with an existing handle. It is up to the caller of this method to ensure that the passed in handle is unique.

Parameters:

handle - A unique HGPersistentHandle that will refer to the link within the HyperGraphDB store.

link - A non-null, but possibly empty array of persistent atom handles that constitute the link to be created.

The - handle parameter.

store

public HGPersistentHandle store(byte[] data)

Write raw binary data to the store. A new persistent handle is created to refer to the data.

Parameters:

A - non-null, but possibly empty byte[] holding the data to write.

Returns:

The newly created HGPersistentHandle that refers to the recorded data.

store

public HGPersistentHandle store(HGPersistentHandle handle,
                       byte[] data)

Write raw binary data to the store using a pre-created, unique persistent handle.

Parameters:

handle - A unique HGPersistentHandle to be recorded as the data key.

A - non-null, but possibly empty byte[] holding the data to write.

Returns:

The handle parameter.

removeLink

public void removeLink(HGPersistentHandle handle)

Remove a link value associated with a HGPersistentHandle key.

removeData

public void removeData(HGPersistentHandle handle)

Remove a raw data value associated with a HGPersistentHandle key.

getLink

public HGPersistentHandle[] getLink(HGPersistentHandle handle)

Retrieve an existing link by its handle.

Parameters:

handle - The persistent handle of the link. A NullPointerException is thrown if this parameter is null.

Returns:

An array of handles forming the link or null if there is no link with that HGPersistentHandle in the database. Note that if the passed in handle points, the behavior is undefined - the method might throw an exception or return an array of invalid links.

containsLink

public boolean containsLink(HGPersistentHandle handle)

Return true if there is a storage link bound to the passed in handle parameter and false otherwise.

containsData

public boolean containsData(HGPersistentHandle handle)

Return true if there is a data item bound to the passed in handle parameter and false otherwise. This may or may not be any faster then calling the getData method and checking for null. It depends no the implementation.

getData

public byte[] getData(HGPersistentHandle handle)

Retrieve the raw data buffer stored at handle.

Parameters:

handle - The HGPersistentHandle of the data. Cannot be null.

Returns:

The data pointed to by handle or null if it could not be found.

getIncidenceResultSet

public HGRandomAccessResult<HGPersistentHandle> getIncidenceResultSet(HGPersistentHandle handle)

Return a HGSearchResult of atom handles in a given atom's incidence set.

Parameters:

handle - The HGPersistentHandle of the atom whose incidence set is desired.

Returns:

The HGSearchResult iterating over the incidence set.

getIncidenceSetCardinality

public long getIncidenceSetCardinality(HGPersistentHandle handle)

Return the number of atoms in the incidence set of a given atom. That is, return the number of links pointing to the atom.

addIncidenceLink

public void addIncidenceLink(HGPersistentHandle targetHandle,
                    HGPersistentHandle linkHandle)

Update the incidence set of an atom with a newly created link pointing to it. This method is only to be used internally by hypergraph.

If the link is already part of the incidence set of this atom, it will not be added again.

Parameters:

targetHandle - The HGPersistentHandle of the atom whose incidence set is to be updated.

linkHandle - The HGPersistentHandle of the new link pointing to that atom.

removeIncidenceLink

public void removeIncidenceLink(HGPersistentHandle handle,
                       HGPersistentHandle oldLink)

Update the incidence set of an atom by removing a link that no longer points to it. This method is only to be used internally by hypergraph.

If the link is not part of the incidence set of this atom, nothing will be done.

Parameters:

handle - The HGPersistentHandle of the atom whose incidence set is to be updated.

oldLink - The HGPersistentHandle of the old link that no longer points to that atom.

removeIncidenceSet

public void removeIncidenceSet(HGPersistentHandle handle)

Remove the whole incidence set of a given handle. This method is normally used only when an atom is being removed from the hypergraph DB.

Parameters:

handle - The handle of the atom whose incidence set must be removed.

getIndex

public <KeyType,ValueType> HGIndex<KeyType,ValueType> getIndex(String name)

Get the HyperGraphDB index with the given name. Return null if no index with that name exists.

getIndex

public <KeyType,ValueType> HGIndex<KeyType,ValueType> getIndex(String name,
                                                      ByteArrayConverter<KeyType> keyConverter,
                                                      ByteArrayConverter<ValueType> valueConverter,
                                                      Comparator<byte[]> comparator,
                                                      boolean allowCreate)

Retrieve an HGIndex by its name. An index will not be automatically created if it does not exists. To create an index, use the createIndex method.

Parameters:

name - The name of the desired index.

Returns:

The HGIndex with the given name or null if no such index exists.

getBidirectionalIndex

public <KeyType,ValueType> HGBidirectionalIndex<KeyType,ValueType> getBidirectionalIndex(String name,
                                                                                ByteArrayConverter<KeyType> keyConverter,
                                                                                ByteArrayConverter<ValueType> valueConverter,
                                                                                Comparator<byte[]> comparator,
                                                                                boolean allowCreate)

Retrieve an existing HGBidirectionalIndex by its name.

Throws:

ClassCastException - is the index with the specified name is not bidirectional.

removeIndex

public void removeIndex(String name)

Remove an index from the database. Note that all entries in this index will be lost.

close

public void close()

Mainly for internal use - invoked by the main HyperGraph instance.

attachOverlayGraph

public void attachOverlayGraph(StorageGraph sgraph)

Reserved to internal use.

detachOverlayGraph

public void detachOverlayGraph()

Reserved to internal use.

hasOverlayGraph

public boolean hasOverlayGraph()

Reserved to internal use.