2 files changed, 16 insertions, 0 deletions
diff --git a/src/mongo/bson/oid.cpp b/src/mongo/bson/oid.cpp
index 92664fd753c..b073c8efa49 100644
--- a/src/mongo/bson/oid.cpp
+++ b/src/mongo/bson/oid.cpp
@@ -50,6 +50,12 @@ namespace mongo {
         boost::hash_combine(seed, z);
     }
 
+    size_t OID::Hasher::operator() (const OID& oid) const {
+        size_t seed = 0;
+        oid.hash_combine(seed);
+        return seed;
+    }
+
     // machine # before folding in the process id
     OID::MachineAndPid OID::ourMachine;
 
diff --git a/src/mongo/bson/oid.h b/src/mongo/bson/oid.h
index b98e070eeac..d5063dc5f1b 100644
--- a/src/mongo/bson/oid.h
+++ b/src/mongo/bson/oid.h
@@ -53,6 +53,16 @@ namespace mongo {
     */
     class OID {
     public:
+
+        /**
+         * Functor compatible with std::hash for std::unordered_{map,set}
+         * Warning: The hash function is subject to change. Do not use in cases where hashes need
+         *          to be consistent across versions.
+         */
+        struct Hasher {
+            size_t operator() (const OID& oid) const;
+        };
+
         OID() : a(0), b(0) { }
 
         enum {