LUCENE-7071: reduce byte copying costs of OfflineSorter

lucene/CHANGES.txt

@@ -6,6 +6,11 @@ http://s.apache.org/luceneversions
 ======================= Lucene 6.1.0 =======================
 (No Changes)
 
+Optimizations
+
+* LUCENE-7071: Reduce bytes copying in OfflineSorter, giving ~10%
+  speedup on merging 2D LatLonPoint values (Mike McCandless)
+
 ======================= Lucene 6.0.0 =======================
 
 System Requirements

lucene/core/src/java/org/apache/lucene/util/ByteBlockPool.java

@@ -280,6 +280,28 @@ public final class ByteBlockPool {
     return newUpto+3;
   }
 
+  /** Fill the provided {@link BytesRef} with the bytes at the specified offset/length slice.
+   *  This will avoid copying the bytes, if the slice fits into a single block; otherwise, it uses
+   *  the provided {@linkl BytesRefBuilder} to copy bytes over. */
+  void setBytesRef(BytesRefBuilder builder, BytesRef result, long offset, int length) {
+    result.length = length;
+
+    int bufferIndex = (int) (offset >> BYTE_BLOCK_SHIFT);
+    byte[] buffer = buffers[bufferIndex];
+    int pos = (int) (offset & BYTE_BLOCK_MASK);
+    if (pos + length <= BYTE_BLOCK_SIZE) {
+      // common case where the slice lives in a single block: just reference the buffer directly without copying
+      result.bytes = buffer;
+      result.offset = pos;
+    } else {
+      // uncommon case: the slice spans at least 2 blocks, so we must copy the bytes:
+      builder.grow(length);
+      result.bytes = builder.get().bytes;
+      result.offset = 0;
+      readBytes(offset, result.bytes, 0, length);
+    }
+  }
+
   // Fill in a BytesRef from term's length & bytes encoded in
   // byte block
   public void setBytesRef(BytesRef term, int textStart) {

lucene/core/src/java/org/apache/lucene/util/BytesRefArray.java

@@ -108,7 +108,23 @@ public final class BytesRefArray {
     }
     throw new IndexOutOfBoundsException("index " + index
         + " must be less than the size: " + lastElement);
-    
+  }
+
+  /** Used only by sort below, to set a {@link BytesRef} with the specified slice, avoiding copying bytes in the common case when the slice
+   *  is contained in a single block in the byte block pool. */
+  private void setBytesRef(BytesRefBuilder spare, BytesRef result, int index) {
+    if (index < lastElement) {
+      int offset = offsets[index];
+      int length;
+      if (index == lastElement - 1) {
+        length = currentOffset - offset;
+      } else {
+        length = offsets[index + 1] - offset;
+      }
+      pool.setBytesRef(spare, result, offset, length);
+    } else {
+      throw new IndexOutOfBoundsException("index " + index + " must be less than the size: " + lastElement);
+    }
   }
   
   private int[] sort(final Comparator<BytesRef> comp) {
@@ -127,25 +143,30 @@ public final class BytesRefArray {
       @Override
       protected int compare(int i, int j) {
         final int idx1 = orderedEntries[i], idx2 = orderedEntries[j];
-        return comp.compare(get(scratch1, idx1), get(scratch2, idx2));
+        setBytesRef(scratch1, scratchBytes1, idx1);
+        setBytesRef(scratch2, scratchBytes2, idx2);
+        return comp.compare(scratchBytes1, scratchBytes2);
       }
       
       @Override
       protected void setPivot(int i) {
         final int index = orderedEntries[i];
-        pivot = get(pivotBuilder, index);
+        setBytesRef(pivotBuilder, pivot, index);
       }
       
       @Override
       protected int comparePivot(int j) {
         final int index = orderedEntries[j];
-        return comp.compare(pivot, get(scratch2, index));
+        setBytesRef(scratch2, scratchBytes2, index);
+        return comp.compare(pivot, scratchBytes2);
       }
 
-      private BytesRef pivot;
+      private final BytesRef pivot = new BytesRef();
-      private final BytesRefBuilder pivotBuilder = new BytesRefBuilder(),
+      private final BytesRef scratchBytes1 = new BytesRef();
-          scratch1 = new BytesRefBuilder(),
+      private final BytesRef scratchBytes2 = new BytesRef();
-          scratch2 = new BytesRefBuilder();
+      private final BytesRefBuilder pivotBuilder = new BytesRefBuilder();
+      private final BytesRefBuilder scratch1 = new BytesRefBuilder();
+      private final BytesRefBuilder scratch2 = new BytesRefBuilder();
     }.sort(0, size());
     return orderedEntries;
   }
@@ -173,6 +194,7 @@ public final class BytesRefArray {
    */
   public BytesRefIterator iterator(final Comparator<BytesRef> comp) {
     final BytesRefBuilder spare = new BytesRefBuilder();
+    final BytesRef result = new BytesRef();
     final int size = size();
     final int[] indices = comp == null ? null : sort(comp);
     return new BytesRefIterator() {
@@ -181,7 +203,8 @@ public final class BytesRefArray {
       @Override
       public BytesRef next() {
         if (pos < size) {
-          return get(spare, indices == null ? pos++ : indices[pos++]);
+          setBytesRef(spare, result, indices == null ? pos++ : indices[pos++]);
+          return result;
         }
         return null;
       }

lucene/core/src/java/org/apache/lucene/util/OfflineSorter.java

@@ -282,7 +282,6 @@ public class OfflineSorter {
 
   /** Sort a single partition in-memory. */
   protected String sortPartition(TrackingDirectoryWrapper trackingDir) throws IOException {
-    BytesRefArray data = this.buffer;
 
     try (IndexOutput tempFile = trackingDir.createTempOutput(tempFileNamePrefix, "sort", IOContext.DEFAULT);
          ByteSequencesWriter out = getWriter(tempFile);) {
@@ -299,7 +298,7 @@ public class OfflineSorter {
       }
       
       // Clean up the buffer for the next partition.
-      data.clear();
+      buffer.clear();
 
       return tempFile.getName();
     }

lucene/suggest/src/java/org/apache/lucene/search/suggest/SortedInputIterator.java

@@ -146,6 +146,7 @@ public class SortedInputIterator implements InputIterator {
     @Override
     public int compare(BytesRef left, BytesRef right) {
       // Make shallow copy in case decode changes the BytesRef:
+      assert left != right;
       leftScratch.bytes = left.bytes;
       leftScratch.offset = left.offset;
       leftScratch.length = left.length;
@@ -245,24 +246,24 @@ public class SortedInputIterator implements InputIterator {
   
   /** decodes the weight at the current position */
   protected long decode(BytesRef scratch, ByteArrayDataInput tmpInput) {
-    tmpInput.reset(scratch.bytes);
+    tmpInput.reset(scratch.bytes, scratch.offset, scratch.length);
     tmpInput.skipBytes(scratch.length - 8); // suggestion
-    scratch.length -= 8; // long
+    scratch.length -= Long.BYTES; // long
     return tmpInput.readLong();
   }
   
   /** decodes the contexts at the current position */
   protected Set<BytesRef> decodeContexts(BytesRef scratch, ByteArrayDataInput tmpInput) {
-    tmpInput.reset(scratch.bytes);
+    tmpInput.reset(scratch.bytes, scratch.offset, scratch.length);
     tmpInput.skipBytes(scratch.length - 2); //skip to context set size
     short ctxSetSize = tmpInput.readShort();
     scratch.length -= 2;
     final Set<BytesRef> contextSet = new HashSet<>();
     for (short i = 0; i < ctxSetSize; i++) {
-      tmpInput.setPosition(scratch.length - 2);
+      tmpInput.setPosition(scratch.offset + scratch.length - 2);
       short curContextLength = tmpInput.readShort();
       scratch.length -= 2;
-      tmpInput.setPosition(scratch.length - curContextLength);
+      tmpInput.setPosition(scratch.offset + scratch.length - curContextLength);
       BytesRef contextSpare = new BytesRef(curContextLength);
       tmpInput.readBytes(contextSpare.bytes, 0, curContextLength);
       contextSpare.length = curContextLength;
@@ -274,10 +275,11 @@ public class SortedInputIterator implements InputIterator {
   
   /** decodes the payload at the current position */
   protected BytesRef decodePayload(BytesRef scratch, ByteArrayDataInput tmpInput) {
-    tmpInput.reset(scratch.bytes);
+    tmpInput.reset(scratch.bytes, scratch.offset, scratch.length);
     tmpInput.skipBytes(scratch.length - 2); // skip to payload size
     short payloadLength = tmpInput.readShort(); // read payload size
-    tmpInput.setPosition(scratch.length - 2 - payloadLength); // setPosition to start of payload
+    assert payloadLength >= 0: payloadLength;
+    tmpInput.setPosition(scratch.offset + scratch.length - 2 - payloadLength); // setPosition to start of payload
     BytesRef payloadScratch = new BytesRef(payloadLength); 
     tmpInput.readBytes(payloadScratch.bytes, 0, payloadLength); // read payload
     payloadScratch.length = payloadLength;