eclipse-rdf4jGH-4819 [LmdbStore] Add initial support for merge joins.

core/sail/lmdb/src/main/java/org/eclipse/rdf4j/sail/lmdb/LmdbSailStore.java

@@ -181,6 +181,8 @@ abstract static class StatefulOperation implements Operation {
 	 */
 	private final AtomicBoolean storeTxnStarted = new AtomicBoolean(false);
 
+	private final Set<StatementOrder> supportedOrders;
+
 	/**
 	 * Creates a new {@link LmdbSailStore}.
 	 */
@@ -203,6 +205,7 @@ protected Long read(ByteBuffer buffer) {
 			namespaceStore = new NamespaceStore(dataDir);
 			valueStore = new ValueStore(new File(dataDir, "values"), config);
 			tripleStore = new TripleStore(new File(dataDir, "triples"), config);
+			supportedOrders = tripleStore.getStatementOrders();
 			contextStore = new ContextStore(this, dataDir);
 			initialized = true;
 		} finally {
@@ -315,7 +318,7 @@ CloseableIteration<Resource> getContexts() throws IOException {
 		CloseableIteration<? extends Statement> stIter1;
 		if (records == null) {
 			// Iterator over all statements
-			stIter1 = createStatementIterator(txn, null, null, null, true);
+			stIter1 = createStatementIterator(null, txn, null, null, null, true);
 		} else {
 			stIter1 = new LmdbStatementIterator(records, valueStore);
 		}
@@ -359,6 +362,7 @@ protected void handleClose() throws SailException {
 	 * @return A StatementIterator that can be used to iterate over the statements that match the specified pattern.
 	 */
 	CloseableIteration<? extends Statement> createStatementIterator(
+			StatementOrder statementOrder,
 			Txn txn, Resource subj, IRI pred, Value obj, boolean explicit, Resource... contexts) throws IOException {
 		long subjID = LmdbValue.UNKNOWN_ID;
 		if (subj != null) {
@@ -405,7 +409,8 @@ CloseableIteration<? extends Statement> createStatementIterator(
 		ArrayList<LmdbStatementIterator> perContextIterList = new ArrayList<>(contextIDList.size());
 
 		for (long contextID : contextIDList) {
-			RecordIterator records = tripleStore.getTriples(txn, subjID, predID, objID, contextID, explicit);
+			RecordIterator records = tripleStore.getTriples(statementOrder, txn, subjID, predID, objID, contextID,
+					explicit);
 			perContextIterList.add(new LmdbStatementIterator(records, valueStore));
 		}
 
@@ -888,7 +893,7 @@ public CloseableIteration<? extends Resource> getContextIDs() throws SailExcepti
 		public CloseableIteration<? extends Statement> getStatements(Resource subj, IRI pred, Value obj,
 				Resource... contexts) throws SailException {
 			try {
-				return createStatementIterator(txn, subj, pred, obj, explicit, contexts);
+				return createStatementIterator(null, txn, subj, pred, obj, explicit, contexts);
 			} catch (IOException e) {
 				throw new SailException("Unable to get statements", e);
 			}
@@ -897,17 +902,25 @@ public CloseableIteration<? extends Statement> getStatements(Resource subj, IRI
 		@Override
 		public CloseableIteration<? extends Statement> getStatements(StatementOrder statementOrder, Resource subj,
 				IRI pred, Value obj, Resource... contexts) throws SailException {
-			throw new UnsupportedOperationException("Not implemented yet");
+			try {
+				return createStatementIterator(statementOrder, txn, subj, pred, obj, explicit, contexts);
+			} catch (IOException e) {
+				throw new SailException("Unable to get statements", e);
+			}
 		}
 
 		@Override
 		public Set<StatementOrder> getSupportedOrders(Resource subj, IRI pred, Value obj, Resource... contexts) {
-			return Set.of();
+			return supportedOrders;
 		}
 
 		@Override
 		public Comparator<Value> getComparator() {
-			throw new UnsupportedOperationException("Not implemented yet");
+			return (a, b) -> {
+				long id1 = (a instanceof LmdbValue) ? ((LmdbValue) a).getInternalID() : 0;
+				long id2 = (b instanceof LmdbValue) ? ((LmdbValue) b).getInternalID() : 0;
+				return Long.compare(id1, id2);
+			};
 		}
 	}
 }

core/sail/lmdb/src/main/java/org/eclipse/rdf4j/sail/lmdb/TripleStore.java

@@ -70,7 +70,10 @@
 import java.util.StringTokenizer;
 import java.util.concurrent.locks.StampedLock;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
+import org.eclipse.rdf4j.common.order.StatementOrder;
 import org.eclipse.rdf4j.sail.SailException;
 import org.eclipse.rdf4j.sail.lmdb.TxnManager.Mode;
 import org.eclipse.rdf4j.sail.lmdb.TxnManager.Txn;
@@ -267,6 +270,24 @@ private void checkVersion() throws SailException {
 		}
 	}
 
+	Set<StatementOrder> getStatementOrders() {
+		Set<String> indexSpecs = getIndexSpecs();
+		return indexSpecs.stream().flatMap(s -> {
+			switch (s.charAt(0)) {
+			case 's':
+				return Stream.of(StatementOrder.S);
+			case 'p':
+				return Stream.of(StatementOrder.P);
+			case 'o':
+				return Stream.of(StatementOrder.O);
+			case 'c':
+				return Stream.of(StatementOrder.C);
+			}
+			return Stream.empty();
+		}
+		).collect(Collectors.toSet());
+	}
+
 	private Set<String> getIndexSpecs() throws SailException {
 		String indexesStr = properties.getProperty(INDEXES_KEY);
 
@@ -288,8 +309,8 @@ TxnManager getTxnManager() {
 	}
 
 	/**
-	 * Parses a comma/whitespace-separated list of index specifications. Index specifications are required to consists
-	 * of 4 characters: 's', 'p', 'o' and 'c'.
+	 * Parses a comma/whitespace-separated list of index specifications. Index specifications are required to consist of
+	 * 4 characters: 's', 'p', 'o' and 'c'.
 	 *
 	 * @param indexSpecStr A string like "spoc, pocs, cosp".
 	 * @return A Set containing the parsed index specifications.
@@ -473,7 +494,26 @@ public RecordIterator getAllTriplesSortedByContext(Txn txn) throws IOException {
 
 	public RecordIterator getTriples(Txn txn, long subj, long pred, long obj, long context, boolean explicit)
 			throws IOException {
-		TripleIndex index = getBestIndex(subj, pred, obj, context);
+		return getTriples(null, txn, subj, pred, obj, context, explicit);
+	}
+
+	public RecordIterator getTriples(StatementOrder statementOrder, Txn txn, long subj, long pred, long obj,
+			long context, boolean explicit)
+			throws IOException {
+		TripleIndex index = null;
+		if (statementOrder != null) {
+			char component = statementOrder.name().toLowerCase().charAt(0);
+			for (TripleIndex candidate : indexes) {
+				if (candidate.fieldSeq[0] == component) {
+					index = candidate;
+				}
+			}
+			if (index == null) {
+				throw new IOException("No index for statement order '" + statementOrder.name() + "' available.");
+			}
+		} else {
+			index = getBestIndex(subj, pred, obj, context);
+		}
 		// System.out.println("get triples: " + Arrays.asList(subj, pred, obj,context));
 		boolean doRangeSearch = index.getPatternScore(subj, pred, obj, context) > 0;
 		return getTriplesUsingIndex(txn, subj, pred, obj, context, explicit, index, doRangeSearch);
@@ -870,7 +910,7 @@ public boolean storeTriple(long subj, long pred, long obj, long context, boolean
 	 */
 	public void removeTriplesByContext(long subj, long pred, long obj, long context,
 			boolean explicit, Consumer<long[]> handler) throws IOException {
-		RecordIterator records = getTriples(txnManager.createTxn(writeTxn), subj, pred, obj, context, explicit);
+		RecordIterator records = getTriples(null, txnManager.createTxn(writeTxn), subj, pred, obj, context, explicit);
 		removeTriples(records, explicit, handler);
 	}
 

core/sail/lmdb/src/test/java/org/eclipse/rdf4j/sail/lmdb/benchmark/QueryBenchmark.java

@@ -87,7 +87,7 @@ public class QueryBenchmark {
 
 	public static void main(String[] args) throws RunnerException {
 		Options opt = new OptionsBuilder()
-				.include("QueryBenchmark") // adapt to control which benchmark tests to run
+				.include("QueryBenchmark.complexQuery") // adapt to control which benchmark tests to run
 				.forks(1)
 				.build();