HBASE-564 Don't do a cache flush if there are zero entries in the cache.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@645690 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -13,6 +13,7 @@ Hbase Change Log
    HBASE-563   TestRowFilterAfterWrite erroneously sets master address to
                0.0.0.0:60100 rather than relying on conf
    HBASE-507   Use Callable pattern to sleep between retries
+   HBASE-564   Don't do a cache flush if there are zero entries in the cache.
 
   NEW FEATURES
    HBASE-548   Tool to online single region

src/java/org/apache/hadoop/hbase/regionserver/HStore.java

@@ -617,6 +617,11 @@ public class HStore implements HConstants {
   private void internalFlushCache(SortedMap<HStoreKey, byte []> cache,
       long logCacheFlushId) throws IOException {
     
+    // Don't flush if there are no entries.
+    if (cache.size() == 0) {
+      return;
+    }
+    
     synchronized(flushLock) {
       // A. Write the Maps out to the disk
       HStoreFile flushedFile = new HStoreFile(conf, fs, basedir,