Github user afs commented on a diff in the pull request: https://github.com/apache/jena/pull/94#discussion_r44383277 --- Diff: jena-arq/src/main/java/org/apache/jena/sparql/core/mem/QuadTable.java --- @@ -0,0 +1,59 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.jena.sparql.core.mem; + +import static org.apache.jena.graph.Node.ANY; + +import java.util.stream.Stream; + +import org.apache.jena.graph.Node; +import org.apache.jena.sparql.core.Quad; + +/** + * A simplex or multiplex table of {@link Quad}s. Implementations may wish to override {@link #listGraphNodes()} with a + * more efficient implementation. + * + */ +public interface QuadTable extends TupleTable<Quad> { + + /** + * Search the table using a pattern of slots. {@link Node#ANY} or <code>null</code> will work as a wildcard. + * + * @param g the graph node of the pattern + * @param s the subject node of the pattern + * @param p the predicate node of the pattern + * @param o the object node of the pattern + * @return an {@link Stream} of matched quads + */ + Stream<Quad> find(Node g, Node s, Node p, Node o); + + /** + * Discover the graphs named in the table + * + * @return an {@link Stream} of graph names used in this table + */ + default Stream<Node> listGraphNodes() { + return find(ANY, ANY, ANY, ANY).map(Quad::getGraph).distinct(); + } --- End diff -- Given the structure, isn't the top level of any index starting with a G enough to get all the graph names? The key set of the FourTupleMap for GSPO is enough, much faster, no retention of state needed for `distinct()`.
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