Module org.apache.jena.core
Package org.apache.jena.mem2.store.roaring

Class RoaringTripleStore

java.lang.Object
org.apache.jena.mem2.store.roaring.RoaringTripleStore
All Implemented Interfaces:
org.apache.jena.atlas.lib.Copyable<TripleStore>, TripleStore
public class RoaringTripleStore extends Object implements TripleStore
A triple store that is ideal for handling extremely large graphs. With the new indexing strategies, it also works well for very small graphs, where pattern matching is not needed.

This store supports different indexing strategies to balance RAM usage and performance for various operations. See IndexingStrategy for details on the available strategies.

Internal structure:

  • One indexed hash set (same as GraphMem2Fast uses) that holds all triples
  • The index consists of three hash maps indexed by subjects, predicates, and objects with RoaringBitmaps as values
  • The bitmaps contain the indices of the triples in the central hash set

The bitmaps are used to quickly find triples that match a given pattern. The bitmap operations like FastAggregation.naive_and(RoaringBitmap...) and RoaringBitmap.intersects(RoaringBitmap, RoaringBitmap) are used to find matches for the pattern S_O, SP_, and _PO pretty fast, even in large graphs.

  • Constructor Details

    • RoaringTripleStore

      public RoaringTripleStore()
      Create a new RoaringTripleStore with the default indexing strategy (EAGER).

      The default strategy is EAGER, because of backwards compatibility. This is not necessarily the best strategy for all use cases, but it reflects the behavior before introducing the indexing strategies.

    • RoaringTripleStore

      public RoaringTripleStore(IndexingStrategy indexingStrategy)
      Create a new RoaringTripleStore with the given indexing strategy.
      Parameters:
      indexingStrategy - the indexing strategy to use

  • Method Details

    • isIndexInitialized

      public boolean isIndexInitialized()
      Check if the index of this store is initialized. This will return true if the current strategy is EagerStoreStrategy, which means that the index has been initialized and all triples are indexed.
      Returns:
      true if the index is initialized, false otherwise

    • getIndexingStrategy

      public IndexingStrategy getIndexingStrategy()
      Get the indexing strategy of this store.
      Returns:
      the indexing strategy

    • clearIndex

      public void clearIndex()
      Clear the index of this store. This will remove all triples from the index and reset the current strategy to the initial one.

    • initializeIndex

      public void initializeIndex()
      Initialize the index for this store.

    • initializeIndexParallel

      public void initializeIndexParallel()
      Initialize the index for this store in parallel. This will index all triples in parallel, which can be faster for large datasets.

    • add

      public void add(Triple triple)
      Description copied from interface: TripleStore
      Add a triple to the map.
      Specified by:
      add in interface TripleStore
      Parameters:
      triple - to add

    • remove

      public void remove(Triple triple)
      Description copied from interface: TripleStore
      Remove a triple from the map.
      Specified by:
      remove in interface TripleStore
      Parameters:
      triple - to remove

    • clear

      public void clear()
      Description copied from interface: TripleStore
      Remove all triples from the map.
      Specified by:
      clear in interface TripleStore

    • countTriples

      public int countTriples()
      Description copied from interface: TripleStore
      Return the number of triples in the map.
      Specified by:
      countTriples in interface TripleStore

    • isEmpty

      public boolean isEmpty()
      Description copied from interface: TripleStore
      Return true if the map is empty.
      Specified by:
      isEmpty in interface TripleStore

    • contains

      public boolean contains(Triple tripleMatch)
      Description copied from interface: TripleStore
      Answer true if the graph contains any triple matching t.
      Specified by:
      contains in interface TripleStore
      Parameters:
      tripleMatch - triple match pattern, which may be contained

    • stream

      public Stream<Triple> stream()
      Description copied from interface: TripleStore
      Returns a Stream of all triples in the graph. Note: BaseStream.parallel() is supported.
      Specified by:
      stream in interface TripleStore
      Returns:
      a stream of triples in this graph.

    • stream

      public Stream<Triple> stream(Triple tripleMatch)
      Description copied from interface: TripleStore
      Returns a Stream of Triples matching the given pattern. Note: BaseStream.parallel() is supported.
      Specified by:
      stream in interface TripleStore
      Parameters:
      tripleMatch - triple match pattern
      Returns:
      a stream of triples in this graph matching the pattern.

    • find

      public ExtendedIterator<Triple> find(Triple tripleMatch)
      Description copied from interface: TripleStore
      Returns an ExtendedIterator of all triples in the graph matching the given triple match.
      Specified by:
      find in interface TripleStore

    • copy

      public RoaringTripleStore copy()
      Description copied from interface: TripleStore
      Return a new triple store that is a copy of this one. Since Nodes and Triples are immutable and shared, the copy can share the same Nodes and Triples.
      Specified by:
      copy in interface org.apache.jena.atlas.lib.Copyable<TripleStore>
      Specified by:
      copy in interface TripleStore
      Returns:
      an independent copy of this store