org.eclipse.rdf4j.sail.lucene

## Class LuceneSail

- java.lang.Object
- - org.eclipse.rdf4j.sail.helpers.SailWrapper
  - - org.eclipse.rdf4j.sail.helpers.NotifyingSailWrapper
    - - org.eclipse.rdf4j.sail.lucene.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:
  - Delete the folder where the data is stored while the application is not running
  - Call the repository's ``RepositoryConnection.clear(org.eclipse.rdf4j.model.Resource[])`` method with no arguments. `clear()`. This will delete the index.

  ## 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 Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `ANALYZER_CLASS_KEY` Set this key as sail parameter to configure the Lucene analyzer class implementation to use for text analysis.
    `static String` | `DEFAULT_INDEX_CLASS`
    `static String` | `DEFAULT_LUCENE_DIR` Set the default directory of the Lucene index files.
    `static String` | `EVALUATION_MODE_KEY` See `TupleFunctionEvaluationMode`.
    `static 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.
    `static String` | `INDEX_CLASS_KEY` Set this key to configure the SearchIndex class implementation.
    `static String` | `INDEXEDFIELDS` Set the parameter "indexedfields=..." to configure a selection of fields to index, and projections of properties.
    `static 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.
    `static String` | `LUCENE_RAMDIR_KEY` Set the key "useramdir=true" as sail parameter to let the LuceneSail store its Lucene index in RAM.
    `static 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.
    `protected Properties` | `parameters`
    `static String` | `REINDEX_QUERY_KEY` Set the parameter "reindexQuery=" to configure the statements to index over.
    `static String` | `SIMILARITY_CLASS_KEY` Set this key as sail parameter to configure `Similarity` class implementation to use for text analysis.
    `static String` | `WKT_FIELDS` Set this key to configure which fields contain WKT and should be spatially indexed.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `LuceneSail()`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected boolean` | `acceptStatementToIndex(Statement s)`
    `protected static SearchIndex` | `createSearchIndex(Properties parameters)` Deprecated.
    `NotifyingSailConnection` | `getConnection()` Opens a connection on the Sail which can be used to query and update data.
    `TupleFunctionEvaluationMode` | `getEvaluationMode()` See EVALUATION_MODE_KEY parameter.
    `FederatedServiceResolver` | `getFederatedServiceResolver()`
    `SearchIndex` | `getLuceneIndex()`
    `String` | `getParameter(String key)`
    `Set<String>` | `getParameterNames()`
    `String` | `getReindexQuery()` See REINDEX_QUERY_KEY parameter.
    `protected Collection<SearchQueryInterpreter>` | `getSearchQueryInterpreters()`
    `TupleFunctionRegistry` | `getTupleFunctionRegistry()`
    `void` | `initialize()` Initializes the Sail.
    `protected void` | `initializeLuceneIndex()`
    `boolean` | `isIncompleteQueryFails()` When this is true, incomplete queries will trigger a SailException.
    `Statement` | `mapStatement(Statement statement)`
    `void` | `registerStatementFilter(IndexableStatementFilter filter)` Sets a filter which determines whether a statement should be considered for indexing when performing complete reindexing.
    `void` | `reindex()` Starts a reindexation process of the whole sail.
    `void` | `setDataDir(File dataDir)` Sets the data directory for the Sail.
    `void` | `setEvaluationMode(TupleFunctionEvaluationMode mode)` See EVALUATION_MODE_KEY parameter.
    `void` | `setFederatedServiceResolver(FederatedServiceResolver resolver)` Sets the `FederatedServiceResolver` to use for this client.
    `void` | `setIncompleteQueryFails(boolean incompleteQueryFails)` Set this to true, so that incomplete queries will trigger a SailException.
    `void` | `setLuceneIndex(SearchIndex luceneIndex)`
    `void` | `setParameter(String key, String value)`
    `void` | `setReindexQuery(String query)` See REINDEX_QUERY_KEY parameter.
    `void` | `setTupleFunctionRegistry(TupleFunctionRegistry registry)`
    `void` | `shutDown()` Shuts down the Sail, giving it the opportunity to synchronize any stale data.

    - ### Methods inherited from class org.eclipse.rdf4j.sail.helpers.NotifyingSailWrapper

      `addSailChangedListener, getBaseSail, removeSailChangedListener, setBaseSail`

    - ### Methods inherited from class org.eclipse.rdf4j.sail.helpers.SailWrapper

      `getDataDir, getDefaultIsolationLevel, getSupportedIsolationLevels, getValueFactory, isWritable, verifyBaseSailSet`

    - ### Methods inherited from class java.lang.Object

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

    - ### Methods inherited from interface org.eclipse.rdf4j.sail.Sail

      `getDataDir, getDefaultIsolationLevel, getSupportedIsolationLevels, getValueFactory, init, isWritable`

- - ### 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

    - #### 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 `TupleFunctionEvaluationMode`.
      See Also:
        Constant Field Values

    - #### parameters

          protected final Properties parameters

  - ### Constructor Detail

    - #### LuceneSail

          public LuceneSail()

  - ### Method Detail

    - #### 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`

    - #### initialize

          public void initialize()
                          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:
        `initialize` in interface `Sail`
      Overrides:
        `initialize` in class `SailWrapper`
      Throws:
        `SailException` - If the Sail could not be initialized.

    - #### createSearchIndex

          @Deprecated
          protected static SearchIndex createSearchIndex(Properties parameters)
                                                              throws Exception

      Deprecated.
      The method is relocated to `SearchIndexUtils.createSearchIndex(java.util.Properties)`.
      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()

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