[LUCENE-5668] Off-by-1 error in TieredMergePolicy

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.8.1, 4.9, 6.0
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 12/May/14 15:37
• Updated: 28/Aug/22 14:07
• Resolved: 12/May/14 19:25

Description

When I was comparing performance of different UUIDs, I noticed that TMP was merging too soon and picking non-ideal merges as a result. The fix is silly:

Index: lucene/core/src/java/org/apache/lucene/index/TieredMergePolicy.java
===================================================================
— lucene/core/src/java/org/apache/lucene/index/TieredMergePolicy.java (revision 1593975)
+++ lucene/core/src/java/org/apache/lucene/index/TieredMergePolicy.java (working copy)
@@ -361,7 +361,7 @@
return spec;
}

• if (eligible.size() >= allowedSegCountInt) {
  + if (eligible.size() > allowedSegCountInt) {

// OK we are over budget – find best merge!
MergeScore bestScore = null;