File	Doc	Category	Size	Date	Package
BatchFetchQueue.java	API Doc	Hibernate 3.2.5	8510	Thu Jun 15 14:41:26 BST 2006	org.hibernate.engine

BatchFetchQueue

• java.lang.Object

Fields Summary
public static final Object	MARKER
private final Map	batchLoadableEntityKeys Defines a sequence of {@link EntityKey} elements that are currently elegible for batch-fetching. Even though this is a map, we only use the keys. A map was chosen in order to utilize a {@link SequencedHashMap} to maintain sequencing as well as uniqueness. TODO : this would be better as a SequencedReferenceSet, but no such beast exists!
private final Map	subselectsByEntityKey A map of {@link SubselectFetch subselect-fetch descriptors} keyed by the {@link EntityKey) against which the descriptor is registered.
private final PersistenceContext	context The owning persistence context.

Constructors Summary
public BatchFetchQueue(PersistenceContext context) Constructs a queue for the given context. param context The owning context. this.context = context;

Methods Summary
public void	addBatchLoadableEntityKey(EntityKey key) If an EntityKey represents a batch loadable entity, add it to the queue. Note that the contract here is such that any key passed in should previously have been been checked for existence within the {@link PersistenceContext}; failure to do so may cause the referenced entity to be included in a batch even though it is already associated with the {@link PersistenceContext}. if ( key.isBatchLoadable() ) { batchLoadableEntityKeys.put( key, MARKER ); }
public void	addSubselect(EntityKey key, SubselectFetch subquery) Adds a subselect fetch decriptor for the given entity key. param key The entity for which to register the subselect fetch. param subquery The fetch descriptor. subselectsByEntityKey.put(key, subquery);
public void	clear() Clears all entries from this fetch queue. batchLoadableEntityKeys.clear(); subselectsByEntityKey.clear();
public void	clearSubselects() Clears all pending subselect fetches from the queue. Called after flushing. subselectsByEntityKey.clear();
public java.io.Serializable[]	getCollectionBatch(org.hibernate.persister.collection.CollectionPersister collectionPersister, java.io.Serializable id, int batchSize, org.hibernate.EntityMode entityMode) Get a batch of uninitialized collection keys for a given role param collectionPersister The persister for the collection role. param id A key that must be included in the batch fetch param batchSize the maximum number of keys to return return an array of collection keys, of length batchSize (padded with nulls) Serializable[] keys = new Serializable[batchSize]; keys[0] = id; int i = 1; //int count = 0; int end = -1; boolean checkForEnd = false; // this only works because collection entries are kept in a sequenced // map by persistence context (maybe we should do like entities and // keep a separate sequences set...) Iterator iter = context.getCollectionEntries().entrySet().iterator(); //TODO: calling entrySet on an IdentityMap is SLOW!! while ( iter.hasNext() ) { Map.Entry me = (Map.Entry) iter.next(); CollectionEntry ce = (CollectionEntry) me.getValue(); PersistentCollection collection = (PersistentCollection) me.getKey(); if ( !collection.wasInitialized() && ce.getLoadedPersister() == collectionPersister ) { if ( checkForEnd && i == end ) { return keys; //the first key found after the given key } //if ( end == -1 && count > batchSize*10 ) return keys; //try out ten batches, max final boolean isEqual = collectionPersister.getKeyType().isEqual( id, ce.getLoadedKey(), entityMode, collectionPersister.getFactory() ); if ( isEqual ) { end = i; //checkForEnd = false; } else if ( !isCached( ce.getLoadedKey(), collectionPersister, entityMode ) ) { keys[i++] = ce.getLoadedKey(); //count++; } if ( i == batchSize ) { i = 1; //end of array, start filling again from start if ( end != -1 ) { checkForEnd = true; } } } } return keys; //we ran out of keys to try
public java.io.Serializable[]	getEntityBatch(org.hibernate.persister.entity.EntityPersister persister, java.io.Serializable id, int batchSize, org.hibernate.EntityMode entityMode) Get a batch of unloaded identifiers for this class, using a slightly complex algorithm that tries to grab keys registered immediately after the given key. param persister The persister for the entities being loaded. param id The identifier of the entity currently demanding load. param batchSize The maximum number of keys to return return an array of identifiers, of length batchSize (possibly padded with nulls) Serializable[] ids = new Serializable[batchSize]; ids[0] = id; //first element of array is reserved for the actual instance we are loading! int i = 1; int end = -1; boolean checkForEnd = false; Iterator iter = batchLoadableEntityKeys.keySet().iterator(); while ( iter.hasNext() ) { EntityKey key = (EntityKey) iter.next(); if ( key.getEntityName().equals( persister.getEntityName() ) ) { //TODO: this needn't exclude subclasses... if ( checkForEnd && i == end ) { //the first id found after the given id return ids; } if ( persister.getIdentifierType().isEqual( id, key.getIdentifier(), entityMode ) ) { end = i; } else { if ( !isCached( key, persister, entityMode ) ) { ids[i++] = key.getIdentifier(); } } if ( i == batchSize ) { i = 1; //end of array, start filling again from start if (end!=-1) checkForEnd = true; } } } return ids; //we ran out of ids to try
public SubselectFetch	getSubselect(EntityKey key) Retrieve the fetch descriptor associated with the given entity key. param key The entity key for which to locate any defined subselect fetch. return The fetch descriptor; may return null if no subselect fetch queued for this entity key. return (SubselectFetch) subselectsByEntityKey.get(key);
private boolean	isCached(EntityKey entityKey, org.hibernate.persister.entity.EntityPersister persister, org.hibernate.EntityMode entityMode) if ( persister.hasCache() ) { CacheKey key = new CacheKey( entityKey.getIdentifier(), persister.getIdentifierType(), entityKey.getEntityName(), entityMode, context.getSession().getFactory() ); return persister.getCache().getCache().get( key ) != null; } return false;
private boolean	isCached(java.io.Serializable collectionKey, org.hibernate.persister.collection.CollectionPersister persister, org.hibernate.EntityMode entityMode) if ( persister.hasCache() ) { CacheKey cacheKey = new CacheKey( collectionKey, persister.getKeyType(), persister.getRole(), entityMode, context.getSession().getFactory() ); return persister.getCache().getCache().get( cacheKey ) != null; } return false;
public void	removeBatchLoadableEntityKey(EntityKey key) After evicting or deleting or loading an entity, we don't need to batch fetch it anymore, remove it from the queue if necessary if ( key.isBatchLoadable() ) batchLoadableEntityKeys.remove(key);
public void	removeSubselect(EntityKey key) After evicting or deleting an entity, we don't need to know the query that was used to load it anymore (don't call this after loading the entity, since we might still need to load its collections) subselectsByEntityKey.remove(key);