updating to include leafyBranchPruning, reducing the number of terms …

…generated for each shape

src/main/java/org/apache/lucene/spatial/prefix/tree/PackedQuadPrefixTree.java

@@ -44,6 +44,8 @@ public class PackedQuadPrefixTree extends QuadPrefixTree {
   public static final byte[] QUAD = new byte[] {0x00, 0x01, 0x02, 0x03};
   public static final int MAX_LEVELS_POSSIBLE = 29;
 
+  private boolean leafyPrune = true;
+
   public static class Factory extends QuadPrefixTree.Factory {
     @Override
     protected SpatialPrefixTree newSPT() {
@@ -121,6 +123,10 @@ public CellIterator getTreeCellIterator(Shape shape, int detailLevel) {
     return new PrefixTreeIterator(shape);
   }
 
+  public void setPruneLeafyBranches( boolean pruneLeafyBranches ) {
+    this.leafyPrune = pruneLeafyBranches;
+  }
+
   /**
    * PackedQuadCell Binary Representation is as follows
    * CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCDDDDDL
@@ -129,7 +135,7 @@ public CellIterator getTreeCellIterator(Shape shape, int detailLevel) {
    *       D = Depth bits (5 with max of 29 levels)
    *       L = isLeaf bit
    */
-  public class PackedQuadCell extends QuadPrefixTree.QuadCell {
+  public class PackedQuadCell extends QuadCell {
     private long term;
 
     PackedQuadCell(long term) {
@@ -170,7 +176,7 @@ public boolean isEnd(final int level, final int shift) {
      * setting this to false will step to the next sibling.
      * Note: This complies with lexicographical ordering, once you've moved to the next sibling there is no backtracking.
      */
-    public Cell nextCell(boolean descend) {
+    public PackedQuadCell nextCell(boolean descend) {
       final int level = getLevel();
       final int shift = getShiftForLevel(level);
       // base case: can't go further
@@ -248,7 +254,7 @@ protected Collection<Cell> getSubCells() {
     }
 
     @Override
-    protected QuadPrefixTree.QuadCell getSubCell(Point p) {
+    protected QuadCell getSubCell(Point p) {
       return (PackedQuadCell) PackedQuadPrefixTree.this.getCell(p, getLevel() + 1);//not performant!
     }
 
@@ -348,11 +354,18 @@ public String toString() {
 
     protected class PrefixTreeIterator extends CellIterator {
     private Shape shape;
+    private PackedQuadCell thisCell;
+    private PackedQuadCell nextCell;
+
+    private short leaves;
+    private short level;
+    private final short maxLevels;
+    private CellIterator pruneIter;
 
     PrefixTreeIterator(Shape shape) {
-      super();
       this.shape = shape;
       this.thisCell = ((PackedQuadCell)(getWorldCell())).nextCell(true);
+      this.maxLevels = (short)thisCell.getMaxLevels();
       this.nextCell = null;
     }
 
@@ -366,31 +379,41 @@ public boolean hasNext() {
       while (thisCell != null) {
         rel = thisCell.getShape().relate(shape);
         if (rel == SpatialRelation.DISJOINT) {
-          thisCell = ((PackedQuadCell) thisCell).nextCell(false);
-        } else if (rel == SpatialRelation.INTERSECTS || rel == SpatialRelation.CONTAINS) {
+          thisCell = thisCell.nextCell(false);
+        } else { // within || intersects || contains
           thisCell.setShapeRel(rel);
           nextCell = thisCell;
-          if (thisCell.getLevel() == getMaxLevels()) {
+          if (rel == SpatialRelation.WITHIN) {
             thisCell.setLeaf();
-            if (shape instanceof Point) {
-              thisCell.setShapeRel(SpatialRelation.WITHIN);
-              thisCell = null;
+            thisCell = thisCell.nextCell(false);
+          } else {  // intersects || contains
+            level = (short) (thisCell.getLevel());
+            if (level == maxLevels || pruned(rel)) {
+              thisCell.setLeaf();
+              if (shape instanceof Point) {
+                thisCell.setShapeRel(SpatialRelation.WITHIN);
+                thisCell = null;
+              } else {
+                thisCell = thisCell.nextCell(false);
+              }
               break;
             }
+            thisCell = thisCell.nextCell(true);
           }
-          thisCell = ((PackedQuadCell) thisCell).nextCell(true);
-          break;
-        } else if (rel == SpatialRelation.WITHIN ) {
-          thisCell.setLeaf();
-          thisCell.setShapeRel(rel);
-          nextCell = thisCell;
-          thisCell = ((PackedQuadCell) thisCell).nextCell(false);
           break;
         }
       }
       return nextCell != null;
     }
 
+    private boolean pruned(SpatialRelation rel) {
+      if (rel == SpatialRelation.INTERSECTS && leafyPrune && level == maxLevels-1) {
+        for (leaves=0, pruneIter=thisCell.getNextLevelCells(shape); pruneIter.hasNext(); pruneIter.next(), ++leaves);
+        return leaves == 4;
+      }
+      return false;
+    }
+
     @Override
     public Cell next() {
       if (nextCell == null) {
@@ -409,5 +432,4 @@ public void remove() {
       //no-op
     }
   }
-
 }