support for ???G, S??G, SP?G & SPOG

hdt-java-core/src/main/java/org/rdfhdt/hdt/quads/impl/BitmapQuadsIteratorG.java

@@ -0,0 +1,95 @@
+package org.rdfhdt.hdt.quads.impl;
+
+import org.rdfhdt.hdt.compact.bitmap.Bitmap;
+import org.rdfhdt.hdt.exceptions.NotImplementedException;
+import org.rdfhdt.hdt.triples.TripleID;
+import org.rdfhdt.hdt.triples.impl.BitmapTriples;
+import org.rdfhdt.hdt.triples.impl.BitmapTriplesIterator;
+
+public class BitmapQuadsIteratorG extends BitmapTriplesIterator {
+
+	// resolves ???G, S??G, SP?G, SPOG queries
+
+	private Bitmap bitmapGraph; // the graph bitmap for the search
+
+	public BitmapQuadsIteratorG(BitmapTriples triples, TripleID pattern) {
+		super();
+		this.triples = triples;
+		this.returnTriple = new TripleID();
+		this.pattern = new TripleID();
+		this.bitmapGraph = triples
+			.getQuadInfoAG()
+			.get((int)pattern.getGraph() - 1);
+		newSearch(pattern);
+	}
+
+	@Override
+	public void goToStart() {
+		if(minZ >= maxZ || minZ == -1) { // no results
+			posZ = maxZ;
+		} else {
+			super.goToStart();
+		}
+		if (!bitmapGraph.access(posZ)) {
+			posZ = bitmapGraph.selectNext1(posZ + 1);
+		}
+	}
+
+	@Override
+	public long estimatedNumResults() {
+		if (minZ == -1) {
+			return 0;
+		}
+		return bitmapGraph.rank1(maxZ - 1) - bitmapGraph.rank1(minZ - 1);
+	}
+
+	/* 
+	 * Check if there are more solution
+	 */
+	@Override
+	public boolean hasNext() {
+		return posZ<maxZ && posZ != -1; // Just check if we have arrived to the maximum position of the objects that resolve the query
+	}
+
+	/* 
+	 * Get the next solution
+	 */
+	@Override
+	public TripleID next() {
+		z = adjZ.get(posZ); // get the next object (Z). We just retrieve it from the list of objects (AdjZ) from current position posZ
+		if(posZ>=nextZ) { // if, with the current position of the object (posZ), we have reached the next list of objects (starting in nexZ), then we should update the associated predicate (Y) and, potentially, also the associated subject (X)
+			posY = triples.bitmapZ.rank1(posZ-1);	// move to the next position of predicates
+			y = adjY.get(posY); // get the next predicate (Y). We just retrieve it from the list of predicates(AdjY) from current position posY
+			nextZ = adjZ.findNext(posZ)+1;	// update nextZ, storing in which position (in adjZ) ends the list of objects associated with the current subject,predicate
+			if(posY>=nextY) { // if we have reached the next list of objects (starting in nexZ) we should update the associated predicate (Y) and, potentially, also the associated subject (X)
+				x = triples.bitmapY.rank1(posY - 1) + 1;	// get the next subject (X)
+				nextY = adjY.findNext(posY)+1;	// update nextY, storing in which position (in AdjY) ends the list of predicates associated with the current subject
+			}
+		}
+		posZ = bitmapGraph.selectNext1(posZ + 1);
+
+		updateOutput(); // set the components (subject,predicate,object,graph) of the returned triple
+		return returnTriple; // return the triple as solution
+	}
+
+	@Override
+	public boolean hasPrevious() {
+		throw new NotImplementedException();
+	}
+
+	@Override
+	public TripleID previous() {
+		throw new NotImplementedException();
+	}
+
+	@Override
+	public boolean canGoTo() {
+		throw new NotImplementedException();
+	}
+
+	@Override
+	public void goTo(long pos) {
+		throw new NotImplementedException();
+	}
+
+}

hdt-java-core/src/main/java/org/rdfhdt/hdt/triples/impl/BitmapQuadTriples.java

@@ -53,6 +53,7 @@
 import org.rdfhdt.hdt.options.ControlInformation;
 import org.rdfhdt.hdt.options.HDTOptions;
 import org.rdfhdt.hdt.quads.impl.BitmapQuadsIterator;
+import org.rdfhdt.hdt.quads.impl.BitmapQuadsIteratorG;
 import org.rdfhdt.hdt.triples.IteratorTripleID;
 import org.rdfhdt.hdt.triples.TempTriples;
 import org.rdfhdt.hdt.triples.TripleID;
@@ -295,15 +296,19 @@ public SuppliableIteratorTripleID search(TripleID pattern) {
 			}
 		}
 
-		SuppliableIteratorTripleID bitIt = new BitmapQuadsIterator(
-			this,
-			pattern
-		);
-		if(patternString.equals("????") || patternString.equals("S???") || patternString.equals("SP??") || patternString.equals("SPO?")) {
+		SuppliableIteratorTripleID bitIt;
+		if (patternString.endsWith("G"))
+			bitIt = new BitmapQuadsIteratorG(this, pattern);
+		else
+			bitIt = new BitmapQuadsIterator(this, pattern);
+		if(    patternString.equals("????") || patternString.equals("???G")
+			|| patternString.equals("S???") || patternString.equals("S??G")
+			|| patternString.equals("SP??") || patternString.equals("SP?G")
+			|| patternString.equals("SPO?") || patternString.equals("SPOG")
+		) {
 			return bitIt;
-		} else {
-			return new SequentialSearchIteratorTripleID(pattern, bitIt);
 		}
+		return new SequentialSearchIteratorTripleID(pattern, bitIt);
 	}
 
 	@Override