LUCENE-2663: don't try to clear prior lock in IndexWriter when create=true

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1003938 13f79535-47bb-0310-9956-ffa450edef68

lucene/CHANGES.txt

@@ -132,6 +132,13 @@ Changes in Runtime Behavior
   changed to enable unmapping by default if supported by the JRE.
   (Mike McCandless, Uwe Schindler, Robert Muir)
 
+* LUCENE-2663: IndexWriter no longer forcefully clears any existing
+  locks when create=true.  This was a holdover from when
+  SimpleFSLockFactory was the default locking implementation, and,
+  even then it was dangerous since it could mask bugs in IndexWriter's
+  usage, allowing applications to accidentally open two writers on the
+  same directory.  (Mike McCandless)
+
 API Changes
 
 * LUCENE-2302, LUCENE-1458, LUCENE-2111, LUCENE-2514: Terms are no longer

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

@@ -1073,11 +1073,6 @@ public class IndexWriter implements Closeable {
       create = !IndexReader.indexExists(directory);
     }
 
-    if (create) {
-      // Clear the write lock in case it's leftover:
-      directory.clearLock(WRITE_LOCK_NAME);
-    }
-
     writeLock = directory.makeLock(WRITE_LOCK_NAME);
 
     if (!writeLock.obtain(writeLockTimeout)) // obtain write lock