1 files changed, 4 insertions, 15 deletions
diff --git a/src/mongo/db/s/auto_split_vector.cpp b/src/mongo/db/s/auto_split_vector.cpp
index 2dcb509f156..8be8c5dde8b 100644
--- a/src/mongo/db/s/auto_split_vector.cpp
+++ b/src/mongo/db/s/auto_split_vector.cpp
@@ -50,16 +50,7 @@
 namespace mongo {
 namespace {
 
-/*
- * BSON arrays are serialized as BSON objects with the index of each element as a string key: for
- * example, the array ["a","b","c"] is going to be serialized as {"0":"a","1":"b","2":"c"}. The
- * minimum size for a BSON object is `BSONObj::kMinBSONLength`.
- *
- * Given that the `vector<BSONObj>` returned by `autoSplitVector` can't be greater than 16MB when
- * serialized, pessimistically assume that each key occupies the highest possible number of bytes.
- */
-const int estimatedAdditionalBytesPerItemInBSONArray{
-    (int)std::to_string(BSONObjMaxUserSize / BSONObj::kMinBSONLength).length()};
+constexpr int estimatedAdditionalBytesPerItemInBSONArray{2};
 
 constexpr int kMaxSplitPointsToReposition{3};
 
@@ -94,11 +85,9 @@ const std::tuple<BSONObj, BSONObj> getMinMaxExtendedBounds(const ShardKeyIndex&
 /*
  * Reshuffle fields according to the shard key pattern.
  */
-auto orderShardKeyFields(const BSONObj& keyPattern, const BSONObj& key) {
-    // Note: It is correct to hydrate the indexKey 'key' with 'keyPattern', because the index key
-    // pattern is a prefix of 'keyPattern'.
-    return dotted_path_support::extractElementsBasedOnTemplate(key.replaceFieldNames(keyPattern),
-                                                               keyPattern);
+auto orderShardKeyFields(const BSONObj& keyPattern, BSONObj& key) {
+    return dotted_path_support::extractElementsBasedOnTemplate(
+        prettyKey(keyPattern, key.getOwned()), keyPattern);
 }
 
 }  // namespace