SERVER-65382 Don't use clientReadable in AutoSplitVector when reordering shard key fields

(cherry picked from commit 56dab5c0dcfbebcc2f5910a82f78dd4678620532)

2 files changed, 17 insertions, 8 deletions

diff --git a/src/mongo/db/s/auto_split_vector.cpp b/src/mongo/db/s/auto_split_vector.cpp
index 0f9544cc25e..2dcb509f156 100644
--- a/src/mongo/db/s/auto_split_vector.cpp
+++ b/src/mongo/db/s/auto_split_vector.cpp
@@ -94,9 +94,11 @@ const std::tuple<BSONObj, BSONObj> getMinMaxExtendedBounds(const ShardKeyIndex&
 /*
  * Reshuffle fields according to the shard key pattern.
  */
-auto orderShardKeyFields(const BSONObj& keyPattern, BSONObj& key) {
-    return dotted_path_support::extractElementsBasedOnTemplate(
-        prettyKey(keyPattern, key.getOwned()), keyPattern);
+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);
 }
 
 }  // namespace
diff --git a/src/mongo/db/s/split_vector.cpp b/src/mongo/db/s/split_vector.cpp
index 276b91951e7..8b232db42a5 100644
--- a/src/mongo/db/s/split_vector.cpp
+++ b/src/mongo/db/s/split_vector.cpp
@@ -57,6 +57,16 @@ BSONObj prettyKey(const BSONObj& keyPattern, const BSONObj& key) {
     return key.replaceFieldNames(keyPattern).clientReadable();
 }
 
+/*
+ * 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);
+}
+
 }  // namespace
 
 std::vector<BSONObj> splitVector(OperationContext* opCtx,
@@ -222,17 +232,14 @@ std::vector<BSONObj> splitVector(OperationContext* opCtx,
         // to be removed at the end. If a key appears more times than entries allowed on a
         // chunk, we issue a warning and split on the following key.
         auto tooFrequentKeys = SimpleBSONObjComparator::kInstance.makeBSONObjSet();
-        splitKeys.push_back(dotted_path_support::extractElementsBasedOnTemplate(
-            prettyKey(shardKeyIdx->keyPattern(), currKey.getOwned()), keyPattern));
+        splitKeys.push_back(orderShardKeyFields(keyPattern, currKey.getOwned()));
 
         while (1) {
             while (PlanExecutor::ADVANCED == state) {
                 currCount++;
 
                 if (currCount > keyCount && !force) {
-                    currKey = dotted_path_support::extractElementsBasedOnTemplate(
-                        prettyKey(shardKeyIdx->keyPattern(), currKey.getOwned()), keyPattern);
-
+                    currKey = orderShardKeyFields(keyPattern, currKey.getOwned());
 
                     const auto compareWithPreviousSplitPoint = currKey.woCompare(splitKeys.back());
                     dassert(compareWithPreviousSplitPoint >= 0,