From 1bc0a2a0a37e689685d1c69a29c24999890deaa0 Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Fri, 13 Jun 2008 19:53:23 +0000
Subject: [PATCH] HBASE-682 unnecessary iteration in HMemcache.internalGet? got
 much better reading performance after break it.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@667631 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                         |  5 ++++-
 .../apache/hadoop/hbase/regionserver/Memcache.java  | 13 ++++++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 633402b12fd..eb5d996e5ec 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -47,8 +47,11 @@ Hbase Change Log
    HBASE-662   UI in table.jsp gives META locations, not the table's regions
                location (Jean-Daniel Cryans via Stack)
    HBASE-676   Bytes.getInt returns a long (Clint Morgan via Stack)
-   HBASE-680   config parameter hbase.io.index.interval  should be
+   HBASE-680   Config parameter hbase.io.index.interval  should be
                hbase.index.interval, according to HBaseMapFile.HbaseWriter
+               (LN via Stack)
+   HBASE-682   Unnecessary iteration in HMemcache.internalGet? got much better
+               reading performance after break it (LN via Stack)
    
   IMPROVEMENTS
    HBASE-559   MR example job to count table rows
diff --git a/src/java/org/apache/hadoop/hbase/regionserver/Memcache.java b/src/java/org/apache/hadoop/hbase/regionserver/Memcache.java
index 368117fe6e8..457f849c754 100644
--- a/src/java/org/apache/hadoop/hbase/regionserver/Memcache.java
+++ b/src/java/org/apache/hadoop/hbase/regionserver/Memcache.java
@@ -514,6 +514,9 @@ class Memcache {
           if (ttl == HConstants.FOREVER ||
                 now < itKey.getTimestamp() + ttl) {
             result.add(new Cell(tailMap.get(itKey), itKey.getTimestamp()));
+            if (numVersions > 0 && result.size() >= numVersions) {
+              break;
+            }
           } else {
             victims.add(itKey);
             if (LOG.isDebugEnabled()) {
@@ -521,15 +524,15 @@ class Memcache {
             }
           }
         }
-      }
-      if (numVersions > 0 && result.size() >= numVersions) {
+      } else {
+        // By L.N. HBASE-684, map is sorted, so we can't find match any more.
         break;
       }
     }
     // Remove expired victims from the map.
-    for (HStoreKey v: victims)
+    for (HStoreKey v: victims) {
       map.remove(v);
-
+    }
     return result;
   }
 
@@ -735,4 +738,4 @@ class Memcache {
       }
     }
   }
-}
\ No newline at end of file
+}