1 files changed, 3 insertions, 1 deletions
diff --git a/include/leveldb/comparator.h b/include/leveldb/comparator.h
index 4e00e4d..c215fac 100644
--- a/include/leveldb/comparator.h
+++ b/include/leveldb/comparator.h
@@ -12,7 +12,9 @@ namespace leveldb {
 class Slice;
 
 // A Comparator object provides a total order across slices that are
-// used as keys in an sstable or a database.
+// used as keys in an sstable or a database.  A Comparator implementation
+// must be thread-safe since leveldb may invoke its methods concurrently
+// from multiple threads.
 class Comparator {
  public:
   virtual ~Comparator();