Row set is accessed under lock, does not need to be a concurrent type

Author: apurtell

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -6812,8 +6812,8 @@ public String toString() {
   public static class RowCommitSequencer {
 
     final AtomicLong sequence = new AtomicLong(EnvironmentEdgeManager.currentTime());
-    final AtomicReference<ConcurrentSkipListSet<HashedBytes>> sequenceRowSet =
-        new AtomicReference<>(new ConcurrentSkipListSet<>());
+    final AtomicReference<HashSet<HashedBytes>> sequenceRowSet =
+        new AtomicReference<>(new HashSet<>());
     final ReentrantLock sequenceRowSetLock = new ReentrantLock();
     final LongAdder yieldCount = new LongAdder();
 
@@ -6823,7 +6823,7 @@ long updateCurrentTime(final long now) {
         // We only care that there is a unique CSLS for each discrete tick.
         if (now != x) {
           // When the clock ticks, we begin a new commit sequence.
-          sequenceRowSet.set(new ConcurrentSkipListSet<>());
+          sequenceRowSet.set(new HashSet<>());
         }
         return now;
       });
@@ -6841,7 +6841,7 @@ boolean checkForOverlap(Collection<RowLock> rowLocks) throws IOException {
         throw (IOException) new InterruptedIOException().initCause(e);
       }
       try {
-        ConcurrentSkipListSet<HashedBytes> rowSet = sequenceRowSet.get();
+        Set<HashedBytes> rowSet = sequenceRowSet.get();
         for (RowLock l: rowLocks) {
           HashedBytes row = ((RowLockImpl)l).context.row;
           if (rowSet.contains(row)) {