SERVER-65016 Remove range deletions as part of `dropCollection`

2 files changed, 11 insertions, 5 deletions

diff --git a/src/mongo/db/s/drop_collection_coordinator.cpp b/src/mongo/db/s/drop_collection_coordinator.cpp
index 7061a240378..3510faf2e1d 100644
--- a/src/mongo/db/s/drop_collection_coordinator.cpp
+++ b/src/mongo/db/s/drop_collection_coordinator.cpp
@@ -68,11 +68,9 @@ DropReply DropCollectionCoordinator::dropCollectionLocally(OperationContext* opC
         csr->clearFilteringMetadataForDroppedCollection(opCtx);
     }
 
-    DropReply result;
-    uassertStatusOK(dropCollection(
-        opCtx, nss, &result, DropCollectionSystemCollectionMode::kDisallowSystemCollectionDrops));
-
-    // Remove all range deletion task documents present on disk for the dropped collection
+    // Remove all range deletion task documents present on disk for the collection to drop. This is
+    // a best-effort tentative considering that migrations are not blocked, hence some new document
+    // may be inserted before actually dropping the collection.
     if (collectionUUID) {
         // The multi-document remove command cannot be run in  transactions, so run it using
         // an alternative client.
@@ -97,6 +95,11 @@ DropReply DropCollectionCoordinator::dropCollectionLocally(OperationContext* opC
         }
     }
 
+    DropReply result;
+    uassertStatusOK(dropCollection(
+        opCtx, nss, &result, DropCollectionSystemCollectionMode::kDisallowSystemCollectionDrops));
+
+
     // Force the refresh of the catalog cache to purge outdated information
     const auto catalog = Grid::get(opCtx)->catalogCache();
     uassertStatusOK(catalog->getCollectionRoutingInfoWithRefresh(opCtx, nss));
diff --git a/src/mongo/db/s/range_deleter_service.cpp b/src/mongo/db/s/range_deleter_service.cpp
index d27c71f3932..954fc10395c 100644
--- a/src/mongo/db/s/range_deleter_service.cpp
+++ b/src/mongo/db/s/range_deleter_service.cpp
@@ -487,6 +487,9 @@ SharedSemiFuture<void> RangeDeleterService::registerTask(
 void RangeDeleterService::deregisterTask(const UUID& collUUID, const ChunkRange& range) {
     auto lock = _acquireMutexFailIfServiceNotUp();
     _rangeDeletionTasks[collUUID].erase(std::make_shared<ChunkRange>(range));
+    if (_rangeDeletionTasks[collUUID].size() == 0) {
+        _rangeDeletionTasks.erase(collUUID);
+    }
 }
 
 int RangeDeleterService::getNumRangeDeletionTasksForCollection(const UUID& collectionUUID) {