Class LuceneSail

All Implemented Interfaces:
FederatedServiceResolverClient, NotifyingSail, Sail, StackableSail

public class LuceneSail extends NotifyingSailWrapper
A LuceneSail wraps an arbitrary existing Sail and extends it with support for full-text search on all Literals.

Setting up a LuceneSail

LuceneSail works in two modes: storing its data into a directory on the harddisk or into a RAMDirectory in RAM (which is discarded when the program ends). Example with storage in a folder:
 // create a sesame memory sail
 MemoryStore memoryStore = new MemoryStore();

 // create a lucenesail to wrap the memorystore
 LuceneSail lucenesail = new LuceneSail();
 // set this parameter to store the lucene index on disk
 lucenesail.setParameter(LuceneSail.LUCENE_DIR_KEY, "./data/mydirectory");

 // wrap memorystore in a lucenesail
 lucenesail.setBaseSail(memoryStore);

 // create a Repository to access the sails
 SailRepository repository = new SailRepository(lucenesail);
 repository.initialize();
 
Example with storage in a RAM directory:
 // create a sesame memory sail
 MemoryStore memoryStore = new MemoryStore();

 // create a lucenesail to wrap the memorystore
 LuceneSail lucenesail = new LuceneSail();
 // set this parameter to let the lucene index store its data in ram
 lucenesail.setParameter(LuceneSail.LUCENE_RAMDIR_KEY, "true");

 // wrap memorystore in a lucenesail
 lucenesail.setBaseSail(memoryStore);

 // create a Repository to access the sails
 SailRepository repository = new SailRepository(lucenesail);
 repository.initialize();
 

Asking full-text queries

Text queries are expressed using the virtual properties of the LuceneSail. An example query looks like this in SPARQL:
 SELECT ?subject ?score ?snippet ?resource WHERE {
 ?subject  [
      a  ;
       "my Lucene query" ;
       ?score ;
       ?snippet ;
       ?resource
   ]
 }
 
When defining queries, these properties type and query are mandatory. Also, the matches relation is mandatory. When one of these misses, the query will not be executed as expected. The failure behavior can be configured, setting the Sail property "incompletequeryfail" to true will throw a SailException when such patterns are found, this is the default behavior to help finding inaccurate queries. Set it to false to have warnings logged instead. Multiple queries can be issued to the sail, the results of the queries will be integrated. Note that you cannot use the same variable for multiple Text queries, if you want to combine text searches, use Lucenes query syntax.

Fields are stored/indexed

All fields are stored and indexed. The "text" fields (gathering all literals) have to be stored, because when a new literal is added to a document, the previous texts need to be copied from the existing document to the new Document, this does not work when they are only "indexed". Fields that are not stored, cannot be retrieved using full-text querying.

Deleting a Lucene index

At the moment, deleting the lucene index can be done in two ways:

Handling of Contexts

Each lucene document contains a field for every contextIDs that contributed to the document. NULL contexts are marked using the String SearchFields.CONTEXT_NULL ("null") and stored in the lucene field SearchFields.CONTEXT_FIELD_NAME ("context"). This means that when adding/appending to a document, all additional context-uris are added to the document. When deleting individual triples, the context is ignored. In clear(Resource ...) we make a query on all Lucene-Documents that were possibly created by this context(s). Given a document D that context C(1-n) contributed to. D' is the new document after clear(). - if there is only one C then D can be safely removed. There is no D' (I hope this is the standard case: like in ontologies, where all triples about a resource are in one document) - if there are multiple C, remember the uri of D, delete D, and query (s,p,o, ?) from the underlying store after committing the operation- this returns the literals of D', add D' as new document This will probably be both fast in the common case and capable enough in the multiple-C case.

Defining the indexed Fields

The property INDEXEDFIELDS is to configure which fields to index and to project a property to another. Syntax:
 # only index label and comment
 index.1=http://www.w3.org/2000/01/rdf-schema#label
 index.2=http://www.w3.org/2000/01/rdf-schema#comment
 # project http://xmlns.com/foaf/0.1/name to rdfs:label
 http\://xmlns.com/foaf/0.1/name=http\://www.w3.org/2000/01/rdf-schema#label
 

Datatypes

Datatypes are ignored in the LuceneSail.
  • Field Details

    • REINDEX_QUERY_KEY

      public static final String REINDEX_QUERY_KEY
      Set the parameter "reindexQuery=" to configure the statements to index over. Default value is "SELECT ?s ?p ?o ?c WHERE {{?s ?p ?o} UNION {GRAPH ?c {?s ?p ?o.}}} ORDER BY ?s" . NB: the query must contain the bindings ?s, ?p, ?o and ?c and must be ordered by ?s.
      See Also:
      Constant Field Values
    • INDEXEDFIELDS

      public static final String INDEXEDFIELDS
      Set the parameter "indexedfields=..." to configure a selection of fields to index, and projections of properties. Only the configured fields will be indexed. A property P projected to Q will cause the index to contain Q instead of P, when triples with P were indexed. Syntax of indexedfields - see above
      See Also:
      Constant Field Values
    • LUCENE_DIR_KEY

      public static final String LUCENE_DIR_KEY
      Set the key "lucenedir=<path>" as sail parameter to configure the Lucene Directory on the filesystem where to store the lucene index.
      See Also:
      Constant Field Values
    • DEFAULT_LUCENE_DIR

      public static final String DEFAULT_LUCENE_DIR
      Set the default directory of the Lucene index files. The value is always relational to the dataDir location as a parent directory.
      See Also:
      Constant Field Values
    • LUCENE_RAMDIR_KEY

      public static final String LUCENE_RAMDIR_KEY
      Set the key "useramdir=true" as sail parameter to let the LuceneSail store its Lucene index in RAM. This is not intended for production environments.
      See Also:
      Constant Field Values
    • MAX_DOCUMENTS_KEY

      public static final String MAX_DOCUMENTS_KEY
      Set the key "maxDocuments=<n>" as sail parameter to limit the maximum number of documents to return from a search query. The default is to return all documents. NB: this may involve extra cost for some SearchIndex implementations as they may have to determine this number.
      See Also:
      Constant Field Values
    • WKT_FIELDS

      public static final String WKT_FIELDS
      Set this key to configure which fields contain WKT and should be spatially indexed. The value should be a space-separated list of URIs. Default is http://www.opengis.net/ont/geosparql#asWKT.
      See Also:
      Constant Field Values
    • INDEX_CLASS_KEY

      public static final String INDEX_CLASS_KEY
      Set this key to configure the SearchIndex class implementation. Default is org.eclipse.rdf4j.sail.lucene.LuceneIndex.
      See Also:
      Constant Field Values
    • DEFAULT_INDEX_CLASS

      public static final String DEFAULT_INDEX_CLASS
      See Also:
      Constant Field Values
    • ANALYZER_CLASS_KEY

      public static final String ANALYZER_CLASS_KEY
      Set this key as sail parameter to configure the Lucene analyzer class implementation to use for text analysis.
      See Also:
      Constant Field Values
    • SIMILARITY_CLASS_KEY

      public static final String SIMILARITY_CLASS_KEY
      Set this key as sail parameter to configure Similarity class implementation to use for text analysis.
      See Also:
      Constant Field Values
    • INCOMPLETE_QUERY_FAIL_KEY

      public static final String INCOMPLETE_QUERY_FAIL_KEY
      Set this key as sail parameter to influence whether incomplete queries are treated as failure (Malformed queries) or whether they are ignored. Set to either "true" or "false". When omitted in the properties, true is default (failure on incomplete queries). see isIncompleteQueryFails()
      See Also:
      Constant Field Values
    • EVALUATION_MODE_KEY

      public static final String EVALUATION_MODE_KEY
      See Also:
      Constant Field Values
    • parameters

      protected final Properties parameters
  • Constructor Details

    • LuceneSail

      public LuceneSail()
  • Method Details

    • setLuceneIndex

      public void setLuceneIndex(SearchIndex luceneIndex)
    • getLuceneIndex

      public SearchIndex getLuceneIndex()
    • getConnection

      public NotifyingSailConnection getConnection() throws SailException
      Description copied from interface: Sail
      Opens a connection on the Sail which can be used to query and update data. Depending on how the implementation handles concurrent access, a call to this method might block when there is another open connection on this Sail.
      Specified by:
      getConnection in interface NotifyingSail
      Specified by:
      getConnection in interface Sail
      Overrides:
      getConnection in class NotifyingSailWrapper
      Throws:
      SailException - If no transaction could be started, for example because the Sail is not writable.
    • shutDown

      public void shutDown() throws SailException
      Description copied from interface: Sail
      Shuts down the Sail, giving it the opportunity to synchronize any stale data. Care should be taken that all initialized Sails are being shut down before an application exits to avoid potential loss of data. Once shut down, a Sail can no longer be used until it is re-initialized.
      Specified by:
      shutDown in interface Sail
      Overrides:
      shutDown in class SailWrapper
      Throws:
      SailException - If the Sail object encountered an error or unexpected situation internally.
    • setDataDir

      public void setDataDir(File dataDir)
      Description copied from interface: Sail
      Sets the data directory for the Sail. The Sail can use this directory for storage of data, parameters, etc. This directory must be set before the Sail is initialized.
      Specified by:
      setDataDir in interface Sail
      Overrides:
      setDataDir in class SailWrapper
    • init

      public void init() throws SailException
      Description copied from interface: Sail
      Initializes the Sail. Care should be taken that required initialization parameters have been set before this method is called. Please consult the specific Sail implementation for information about the relevant parameters.
      Specified by:
      init in interface Sail
      Overrides:
      init in class SailWrapper
      Throws:
      SailException - If the Sail could not be initialized.
    • createSearchIndex

      @Deprecated protected static SearchIndex createSearchIndex(Properties parameters) throws Exception
      Deprecated.
      Parameters:
      parameters -
      Returns:
      search index
      Throws:
      Exception
    • initializeLuceneIndex

      protected void initializeLuceneIndex() throws Exception
      Throws:
      Exception
    • setParameter

      public void setParameter(String key, String value)
    • getParameter

      public String getParameter(String key)
    • getParameterNames

      public Set<String> getParameterNames()
    • getReindexQuery

      public String getReindexQuery()
      See REINDEX_QUERY_KEY parameter.
    • setReindexQuery

      public void setReindexQuery(String query)
      See REINDEX_QUERY_KEY parameter.
    • isIncompleteQueryFails

      public boolean isIncompleteQueryFails()
      When this is true, incomplete queries will trigger a SailException. You can set this value either using setIncompleteQueryFails(boolean) or using the parameter "incompletequeryfail"
      Returns:
      Returns the incompleteQueryFails.
    • setIncompleteQueryFails

      public void setIncompleteQueryFails(boolean incompleteQueryFails)
      Set this to true, so that incomplete queries will trigger a SailException. Otherwise, incomplete queries will be logged with level WARN. Default is true. You can set this value also using the parameter "incompletequeryfail".
      Parameters:
      incompleteQueryFails - true or false
    • getEvaluationMode

      public TupleFunctionEvaluationMode getEvaluationMode()
      See EVALUATION_MODE_KEY parameter.
    • setEvaluationMode

      public void setEvaluationMode(TupleFunctionEvaluationMode mode)
      See EVALUATION_MODE_KEY parameter.
    • getTupleFunctionRegistry

      public TupleFunctionRegistry getTupleFunctionRegistry()
    • setTupleFunctionRegistry

      public void setTupleFunctionRegistry(TupleFunctionRegistry registry)
    • getFederatedServiceResolver

      public FederatedServiceResolver getFederatedServiceResolver()
    • setFederatedServiceResolver

      public void setFederatedServiceResolver(FederatedServiceResolver resolver)
      Description copied from interface: FederatedServiceResolverClient
      Sets the FederatedServiceResolver to use for this client.
      Specified by:
      setFederatedServiceResolver in interface FederatedServiceResolverClient
      Overrides:
      setFederatedServiceResolver in class SailWrapper
      Parameters:
      resolver - The resolver to use.
    • reindex

      public void reindex() throws Exception
      Starts a reindexation process of the whole sail. Basically, this will delete and add all data again, a long-lasting process.
      Throws:
      IOException
      Exception
    • registerStatementFilter

      public void registerStatementFilter(IndexableStatementFilter filter)
      Sets a filter which determines whether a statement should be considered for indexing when performing complete reindexing.
    • acceptStatementToIndex

      protected boolean acceptStatementToIndex(Statement s)
    • mapStatement

      public Statement mapStatement(Statement statement)
    • getSearchQueryInterpreters

      protected Collection<SearchQueryInterpreter> getSearchQueryInterpreters()