SparqlView.cs

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namespace VDS.RDF.Query
{
    /// <summary>
    /// Represents a SPARQL View over an in-memory store.
    /// </summary>
    public class SparqlView
        : BaseSparqlView
    {

        /// <summary>
        /// Creates a new SPARQL View.
        /// </summary>
        /// <param name="sparqlQuery">SPARQL Query.</param>
        /// <param name="store">Triple Store to query.</param>
        public SparqlView(string sparqlQuery, IInMemoryQueryableStore store)
            : base(sparqlQuery, store) { }

        /// <summary>
        /// Creates a new SPARQL View.
        /// </summary>
        /// <param name="sparqlQuery">SPARQL Query.</param>
        /// <param name="store">Triple Store to query.</param>
        public SparqlView(SparqlParameterizedString sparqlQuery, IInMemoryQueryableStore store)
            : this(sparqlQuery.ToString(), store) { }

        /// <summary>
        /// Creates a new SPARQL View.
        /// </summary>
        /// <param name="sparqlQuery">SPARQL Query.</param>
        /// <param name="store">Triple Store to query.</param>
        public SparqlView(SparqlQuery sparqlQuery, IInMemoryQueryableStore store)
            : base(sparqlQuery, store) { }

        /// <summary>
        /// Updates the view by making the SPARQL Query in-memory over the relevant Triple Store.
        /// </summary>
        protected override void UpdateViewInternal()
        {
            try
            {
                var processor = new LeviathanQueryProcessor((IInMemoryQueryableStore)_store);
                var results = processor.ProcessQuery(_q);
                if (results is IGraph g)
                {
                    // Note that we replace the existing triple collection with an entirely new one as otherwise nasty race conditions can happen
                    // This does mean that while the update is occurring the user may be viewing a stale graph
                    DetachEventHandlers(_triples);
                    TreeIndexedTripleCollection triples = new TreeIndexedTripleCollection();
                    foreach (Triple t in g.Triples)
                    {
                        triples.Add(t.CopyTriple(this));
                    }
                    _triples = triples;
                    AttachEventHandlers(_triples);
                }
                else
                {
                    // Note that we replace the existing triple collection with an entirely new one as otherwise nasty race conditions can happen
                    // This does mean that while the update is occurring the user may be viewing a stale graph
                    DetachEventHandlers(_triples);
                    _triples = ((SparqlResultSet)results).ToTripleCollection(this);
                    AttachEventHandlers(_triples);
                }
                LastError = null;
                RaiseGraphChanged();
            }
            catch (RdfQueryException queryEx)
            {
                LastError = new RdfQueryException("Unable to Update a SPARQL View as an error occurred in processing the Query - see Inner Exception for details", queryEx);
            }
        }
    }
}