LUCENE-3210: let app control how aggressive TMP is in targetting segments with deletions; default it to more aggressive than today

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1137060 13f79535-47bb-0310-9956-ffa450edef68

lucene/CHANGES.txt

@@ -545,6 +545,10 @@ New Features
 
 * LUCENE-3179: Added OpenBitSet.prevSetBit (Paul Elschot via Mike McCandless)
 
+* LUCENE-3210: Made TieredMergePolicy more aggressive in reclaiming
+  segments with deletions; added new methods
+  set/getReclaimDeletesWeight to control this.  (Mike McCandless)
+
 Build
 
 * LUCENE-1344: Create OSGi bundle using dev-tools/maven.

lucene/src/java/org/apache/lucene/index/TieredMergePolicy.java

@@ -82,6 +82,7 @@ public class TieredMergePolicy extends MergePolicy {
   private double expungeDeletesPctAllowed = 10.0;
   private boolean useCompoundFile = true;
   private double noCFSRatio = 0.1;
+  private double reclaimDeletesWeight = 2.0;
 
   /** Maximum number of segments to be merged at a time
    *  during "normal" merging.  For explicit merging (eg,
@@ -133,6 +134,23 @@ public class TieredMergePolicy extends MergePolicy {
     return maxMergedSegmentBytes/1024/1024.;
   }
 
+  /** Controls how aggressively merges that reclaim more
+   *  deletions are favored.  Higher values favor selecting
+   *  merges that reclaim deletions.  A value of 0.0 means
+   *  deletions don't impact merge selection. */
+  public TieredMergePolicy setReclaimDeletesWeight(double v) {
+    if (v < 0.0) {
+      throw new IllegalArgumentException("reclaimDeletesWeight must be >= 0.0 (got " + v + ")");
+    }
+    reclaimDeletesWeight = v;
+    return this;
+  }
+
+  /** See {@link #setReclaimDeletesWeight}. */
+  public double getReclaimDeletesWeight() {
+    return reclaimDeletesWeight;
+  }
+
   /** Segments smaller than this are "rounded up" to this
    *  size, ie treated as equal (floor) size for merge
    *  selection.  This is to prevent frequent flushing of
@@ -435,7 +453,7 @@ public class TieredMergePolicy extends MergePolicy {
 
     // Strongly favor merges that reclaim deletes:
     final double nonDelRatio = ((double) totAfterMergeBytes)/totBeforeMergeBytes;
-    mergeScore *= nonDelRatio;
+    mergeScore *= Math.pow(nonDelRatio, reclaimDeletesWeight);
 
     final double finalMergeScore = mergeScore;
 

lucene/src/test-framework/org/apache/lucene/util/LuceneTestCase.java

@@ -947,6 +947,7 @@ public abstract class LuceneTestCase extends Assert {
     tmp.setSegmentsPerTier(_TestUtil.nextInt(r, 2, 20));
     tmp.setUseCompoundFile(r.nextBoolean());
     tmp.setNoCFSRatio(0.1 + r.nextDouble()*0.8);
+    tmp.setReclaimDeletesWeight(r.nextDouble()*4);
     return tmp;
   }