working on new ID based join iterator

Author: hmottestad

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

@@ -150,10 +150,10 @@ private void initializeInternal(TripleIndex index, KeyBuilder keyBuilder, boolea
 //		}
 
 		this.index = index;
-		long prevSubj = this.subj;
-		long prevPred = this.pred;
-		long prevObj = this.obj;
-		long prevContext = this.context;
+		long prevSubj = minKeyBuf != null ? this.subj : TripleStore.NO_PREVIOUS_ID;
+		long prevPred = minKeyBuf != null ? this.pred : TripleStore.NO_PREVIOUS_ID;
+		long prevObj = minKeyBuf != null ? this.obj : TripleStore.NO_PREVIOUS_ID;
+		long prevContext = minKeyBuf != null ? this.context : TripleStore.NO_PREVIOUS_ID;
 
 		this.subj = subj;
 		this.pred = pred;

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

@@ -123,6 +123,7 @@ public class TripleStore implements Closeable {
 	public static final int CONTEXT_IDX = 3;
 
 	static final int MAX_KEY_LENGTH = 4 * 9;
+	static final long NO_PREVIOUS_ID = Long.MIN_VALUE;
 
 	/**
 	 * The default triple indexes.
@@ -812,7 +813,8 @@ protected void filterUsedIds(Collection<Long> ids) throws IOException {
 								maxKey.mv_data(maxKeyBuf);
 
 								keyBuf.clear();
-								index.getMinKey(keyBuf, subj, pred, obj, context, 0, 0, 0, 0);
+								index.getMinKey(keyBuf, subj, pred, obj, context, NO_PREVIOUS_ID, NO_PREVIOUS_ID,
+										NO_PREVIOUS_ID, NO_PREVIOUS_ID);
 								keyBuf.flip();
 
 								// set cursor to min key
@@ -918,7 +920,8 @@ private double estimateWithTransaction(Pool pool, Statistics statistics, MemoryS
 				statistics.reset();
 
 				keyBuf.clear();
-				index.getMinKey(keyBuf, subj, pred, obj, context, 0, 0, 0, 0);
+				index.getMinKey(keyBuf, subj, pred, obj, context, NO_PREVIOUS_ID, NO_PREVIOUS_ID, NO_PREVIOUS_ID,
+						NO_PREVIOUS_ID);
 				keyBuf.flip();
 
 				int dbi = index.getDB(explicit);
@@ -1888,7 +1891,8 @@ KeyBuilder keyBuilder(long subj, long pred, long obj, long context) {
 
 				@Override
 				public void writeMin(ByteBuffer buffer) {
-					getMinKey(buffer, subj, pred, obj, context, 0, 0, 0, 0);
+					getMinKey(buffer, subj, pred, obj, context, NO_PREVIOUS_ID, NO_PREVIOUS_ID, NO_PREVIOUS_ID,
+							NO_PREVIOUS_ID);
 				}
 
 				@Override
@@ -1904,7 +1908,12 @@ void getMinKey(ByteBuffer bb, long subj, long pred, long obj, long context, long
 			pred = pred <= 0 ? 0 : pred;
 			obj = obj <= 0 ? 0 : obj;
 			context = context <= 0 ? 0 : context;
-			toKey(bb, subj, pred, obj, context);
+			long prevSubjNorm = prevSubj == NO_PREVIOUS_ID ? NO_PREVIOUS_ID : (prevSubj <= 0 ? 0 : prevSubj);
+			long prevPredNorm = prevPred == NO_PREVIOUS_ID ? NO_PREVIOUS_ID : (prevPred <= 0 ? 0 : prevPred);
+			long prevObjNorm = prevObj == NO_PREVIOUS_ID ? NO_PREVIOUS_ID : (prevObj <= 0 ? 0 : prevObj);
+			long prevContextNorm = prevContext == NO_PREVIOUS_ID ? NO_PREVIOUS_ID
+					: (prevContext <= 0 ? 0 : prevContext);
+			toKey(bb, subj, pred, obj, context, prevSubjNorm, prevPredNorm, prevObjNorm, prevContextNorm);
 		}
 
 		void getMaxKey(ByteBuffer bb, long subj, long pred, long obj, long context) {
@@ -1996,6 +2005,11 @@ public void print() {
 		}
 
 		void toKey(ByteBuffer bb, long subj, long pred, long obj, long context) {
+			toKey(bb, subj, pred, obj, context, NO_PREVIOUS_ID, NO_PREVIOUS_ID, NO_PREVIOUS_ID, NO_PREVIOUS_ID);
+		}
+
+		void toKey(ByteBuffer bb, long subj, long pred, long obj, long context, long prevSubj, long prevPred,
+				long prevObj, long prevContext) {
 
 			boolean shouldCache = threeOfFourAreZeroOrMax(subj, pred, obj, context);
 			if (shouldCache) {
@@ -2012,7 +2026,9 @@ void toKey(ByteBuffer bb, long subj, long pred, long obj, long context) {
 			}
 
 			// Pass through to the keyWriter with caching hint
-			keyWriter.write(bb, subj, pred, obj, context, shouldCache);
+			boolean hasPrev = prevSubj != NO_PREVIOUS_ID;
+			keyWriter.write(bb, subj, pred, obj, context, shouldCache, hasPrev, prevSubj, prevPred, prevObj,
+					prevContext);
 		}
 
 		void keyToQuad(ByteBuffer key, long[] quad) {

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

@@ -246,6 +246,18 @@ public static int calcListLengthUnsigned(long a, long b, long c, long d) {
 		return calcLengthUnsigned(a) + calcLengthUnsigned(b) + calcLengthUnsigned(c) + calcLengthUnsigned(d);
 	}
 
+	/**
+	 * Advances the {@link ByteBuffer#position()} by the number of bytes required to encode the supplied value using the
+	 * unsigned variable-length format, without writing any data. This assumes the buffer already contains the encoded
+	 * representation at the current position.
+	 *
+	 * @param bb    buffer whose position should be advanced
+	 * @param value value whose encoded length should be skipped
+	 */
+	public static void advanceUnsigned(ByteBuffer bb, long value) {
+		bb.position(bb.position() + calcLengthUnsigned(value));
+	}
+
 	/**
 	 * The number of bytes required to represent the given number minus one. The descriptor can be encoded in 3 bits.
 	 *