2 files changed, 23 insertions, 12 deletions

diff --git a/src/mongo/s/database_version.cpp b/src/mongo/s/database_version.cpp
index e2043e39299..b2797ba4c87 100644
--- a/src/mongo/s/database_version.cpp
+++ b/src/mongo/s/database_version.cpp
@@ -66,23 +66,30 @@ BSONObj ComparableDatabaseVersion::toBSONForLogging() const {
 }
 
 bool ComparableDatabaseVersion::operator==(const ComparableDatabaseVersion& other) const {
-    if (!_dbVersion && !other._dbVersion)
-        return true;  // Default constructed value
-    if (_dbVersion.is_initialized() != other._dbVersion.is_initialized())
-        return false;  // One side is default constructed value
-
-    return *_dbVersion == *other._dbVersion;
+    return _dbVersion == other._dbVersion;
 }
 
 bool ComparableDatabaseVersion::operator<(const ComparableDatabaseVersion& other) const {
-    if (!_dbVersion && !other._dbVersion)
-        return false;  // Default constructed value
+    // 1. If both versions are valid and have timestamps
+    //    1.1. if their timestamps are the same -> rely on lastMod to define the order
+    //    1.2. Otherwise  -> rely on the timestamps values to define order
+    // 2. If both versions are valid and have the same uuid -> rely on lastMod to define the order
+    // 3. Any other scenario -> rely on disambiguating sequence number
+    if (_dbVersion && other._dbVersion) {
+        const auto timestamp = _dbVersion->getTimestamp();
+        const auto otherTimestamp = other._dbVersion->getTimestamp();
+        if (timestamp && otherTimestamp) {
+            if (*timestamp == *otherTimestamp)
+                return _dbVersion->getLastMod() < other._dbVersion->getLastMod();
+            else
+                return *timestamp < *otherTimestamp;
 
-    if (_dbVersion && other._dbVersion && _dbVersion->getUuid() == other._dbVersion->getUuid()) {
-        return _dbVersion->getLastMod() < other._dbVersion->getLastMod();
-    } else {
-        return _uuidDisambiguatingSequenceNum < other._uuidDisambiguatingSequenceNum;
+        } else if (_dbVersion->getUuid() == other._dbVersion->getUuid()) {
+            return _dbVersion->getLastMod() < other._dbVersion->getLastMod();
+        }
     }
+
+    return _uuidDisambiguatingSequenceNum < other._uuidDisambiguatingSequenceNum;
 }
 
 }  // namespace mongo
diff --git a/src/mongo/s/database_version.h b/src/mongo/s/database_version.h
index adaa1ff3963..82fe6c9bab7 100644
--- a/src/mongo/s/database_version.h
+++ b/src/mongo/s/database_version.h
@@ -46,6 +46,7 @@ namespace mongo {
 class DatabaseVersion : private DatabaseVersionBase {
 public:
     using DatabaseVersionBase::getLastMod;
+    using DatabaseVersionBase::getTimestamp;
     using DatabaseVersionBase::toBSON;
 
     // It returns a new DatabaseVersion marked as fixed. A fixed database version is used to
@@ -76,6 +77,9 @@ public:
 
     DatabaseVersion makeUpdated() const;
 
+    /**
+     * It returns true if the uuid and lastmod of both versions are the same.
+     */
     bool operator==(const DatabaseVersion& other) const {
         return getUuid() == other.getUuid() && getLastMod() == other.getLastMod();
     }