SERVER-40026 Don't allow distinct on sharded collections in multi document transactions

1 files changed, 10 insertions, 0 deletions

diff --git a/src/mongo/db/commands/distinct.cpp b/src/mongo/db/commands/distinct.cpp
index 1679ea78656..59d86a5acf6 100644
--- a/src/mongo/db/commands/distinct.cpp
+++ b/src/mongo/db/commands/distinct.cpp
@@ -53,6 +53,8 @@
 #include "mongo/db/query/plan_summary_stats.h"
 #include "mongo/db/query/query_planner_common.h"
 #include "mongo/db/query/view_response_formatter.h"
+#include "mongo/db/s/collection_sharding_state.h"
+#include "mongo/db/transaction_participant.h"
 #include "mongo/db/views/resolved_view.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/log.h"
@@ -180,6 +182,14 @@ public:
                     AutoGetCollection::ViewMode::kViewsPermitted);
         const auto& nss = ctx->getNss();
 
+        // Distinct doesn't filter orphan documents so it is not allowed to run on sharded
+        // collections in multi-document transactions.
+        auto txnParticipant = TransactionParticipant::get(opCtx);
+        uassert(ErrorCodes::OperationNotSupportedInTransaction,
+                "Cannot run 'distinct' on a sharded collection in a multi-document transaction.",
+                !txnParticipant || !txnParticipant.inMultiDocumentTransaction() ||
+                    !CollectionShardingState::get(opCtx, nss)->getCurrentMetadata()->isSharded());
+
         const ExtensionsCallbackReal extensionsCallback(opCtx, &nss);
         auto defaultCollation =
             ctx->getCollection() ? ctx->getCollection()->getDefaultCollator() : nullptr;