Package org.eclipse.rdf4j.sail.lucene

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 (SERQL): SELECT Subject, Score, Snippet FROM {Subject} {} {}; {"my Lucene query"}; {Score}; {Snippet}

    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

    Set and select Lucene sail by id

    The property INDEX_ID is to configure the id of the index and filter every request without the search:indexid predicate, the request would be: 
     ?subj search:matches [
              search:indexid my:lucene_index_id;
              search:query "search terms...";
              search:property my:property;
              search:score ?score;
              search:snippet ?snippet ] .

    If a LuceneSail is using another LuceneSail as a base sail, the evaluation mode should be set to TupleFunctionEvaluationMode.NATIVE.

    Defining the indexed Types/Languages

    The properties INDEXEDTYPES and INDEXEDLANG are to configure which fields to index by their language or type. INDEXEDTYPES Syntax: 
     # only index object of rdf:type ex:mytype1, rdf:type ex:mytype2 or ex:mytypedef ex:mytype3
 http\://www.w3.org/1999/02/22-rdf-syntax-ns#type=http://example.org/mytype1 http://example.org/mytype2
 http\://example.org/mytypedef=http://example.org/mytype3

    INDEXEDLANG Syntax: 

     # syntax to index only French(fr) and English(en) literals
 fr en

    Datatypes

    Datatypes are ignored in the LuceneSail.

    • Field Detail

      • 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

      • INDEXEDTYPES

        public static final String INDEXEDTYPES
        Set the parameter "indexedtypes=..." to configure a selection of field type to index. Only the fields with the specific type will be indexed. Syntax of indexedtypes - see above
        See Also:
        Constant Field Values

      • INDEXEDLANG

        public static final String INDEXEDLANG
        Set the parameter "indexedlang=..." to configure a selection of field language to index. Only the fields with the specific language will be indexed. Syntax of indexedlang - 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

      • INDEX_ID

        public static final String INDEX_ID
        Set this key to configure the filtering of queries, if this parameter is set, the match object should contain the search:indexid parameter, see the syntax above
        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

      • FUZZY_PREFIX_LENGTH_KEY

        public static final String FUZZY_PREFIX_LENGTH_KEY
        Set this key as sail parameter to influence the fuzzy prefix length.
        See Also:
        Constant Field Values

      • parameters

        protected final Properties parameters

    • Constructor Detail

      • LuceneSail

        public LuceneSail()

    • Method Detail

      • setLuceneIndex

        public void setLuceneIndex​(SearchIndex luceneIndex)

      • 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.

      • initializeLuceneIndex

        protected void initializeLuceneIndex()
                              throws Exception
        Throws:
        Exception

      • setParameter

        public void setParameter​(String key,
                         String value)

      • 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

      • setFuzzyPrefixLength

        public void setFuzzyPrefixLength​(int fuzzyPrefixLength)

      • reindex

        public void reindex()
             throws SailException
        Starts a reindexation process of the whole sail. Basically, this will delete and add all data again, a long-lasting process.
        Throws:
        SailException - If the Sail could not be reindex

      • 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)