From 1cdc4e655e80ca48c1bc8d4f8bf402c21a60a8f5 Mon Sep 17 00:00:00 2001
From: "Chris M. Hostetter" <hossman@apache.org>
Date: Fri, 1 Oct 2010 23:21:49 +0000
Subject: [PATCH] SOLR-2135: Fix behavior of ConcurrentLRUCache when asking for
 getLatestAccessedItems(0) or getOldestAccessedItems(0)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1003703 13f79535-47bb-0310-9956-ffa450edef68
---
 solr/CHANGES.txt                                          | 4 ++++
 .../org/apache/solr/common/util/ConcurrentLRUCache.java   | 4 ++++
 .../src/test/org/apache/solr/search/TestFastLRUCache.java | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 019f93b58bb..31510ff42c1 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -505,6 +505,10 @@ Bug Fixes
   wildcard support. For example, a query of *zemog* would match documents that contain
   'gomez'.  (Landon Kuhn via Robert Muir)
 
+* SOLR-2135: Fix behavior of ConcurrentLRUCache when asking for
+  getLatestAccessedItems(0) or getOldestAccessedItems(0).
+  (David Smiley via hossman)
+
 Other Changes
 ----------------------
 
diff --git a/solr/src/common/org/apache/solr/common/util/ConcurrentLRUCache.java b/solr/src/common/org/apache/solr/common/util/ConcurrentLRUCache.java
index ac21ef4f2d0..ed352f2e186 100644
--- a/solr/src/common/org/apache/solr/common/util/ConcurrentLRUCache.java
+++ b/solr/src/common/org/apache/solr/common/util/ConcurrentLRUCache.java
@@ -398,6 +398,8 @@ public class ConcurrentLRUCache<K,V> {
    */
   public Map<K, V> getOldestAccessedItems(int n) {
     Map<K, V> result = new LinkedHashMap<K, V>();
+    if (n <= 0)
+      return result;
     TreeSet<CacheEntry> tree = new TreeSet<CacheEntry>();
     markAndSweepLock.lock();
     try {
@@ -424,6 +426,8 @@ public class ConcurrentLRUCache<K,V> {
 
   public Map<K,V> getLatestAccessedItems(int n) {
     Map<K,V> result = new LinkedHashMap<K,V>();
+    if (n <= 0)
+      return result;
     TreeSet<CacheEntry> tree = new TreeSet<CacheEntry>();
     // we need to grab the lock since we are changing lastAccessedCopy
     markAndSweepLock.lock();
diff --git a/solr/src/test/org/apache/solr/search/TestFastLRUCache.java b/solr/src/test/org/apache/solr/search/TestFastLRUCache.java
index 5733bf2b295..6c42eacf283 100644
--- a/solr/src/test/org/apache/solr/search/TestFastLRUCache.java
+++ b/solr/src/test/org/apache/solr/search/TestFastLRUCache.java
@@ -243,6 +243,14 @@ public class TestFastLRUCache extends LuceneTestCase {
     assertNotNull(m.get(5));
     assertNotNull(m.get(4));
     assertNotNull(m.get(2));
+
+    m = cache.getOldestAccessedItems(0);
+    assertTrue(m.isEmpty());
+
+    //test this too
+    m = cache.getLatestAccessedItems(0);
+    assertTrue(m.isEmpty());
+
     cache.destroy();
   }