SERVER-35789 check for index catalog isready mismatch for multi-doc txns

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.cpp b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
index d12ad9e3b74..f44e5a0f31e 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
@@ -162,6 +162,17 @@ const RecordId& IndexCatalogEntryImpl::head(OperationContext* opCtx) const {
 }
 
 bool IndexCatalogEntryImpl::isReady(OperationContext* opCtx) const {
+    auto session = OperationContextSession::get(opCtx);
+    // For multi-document transactions, we can open a snapshot prior to checking the
+    // minimumSnapshotVersion on a collection.  This means we are unprotected from reading
+    // out-of-sync index catalog entries.  To fix this, we uassert if we detect that the
+    // in-memory catalog is out-of-sync with the on-disk catalog.
+    if (session && session->inMultiDocumentTransaction() && _catalogIsReady(opCtx) != _isReady) {
+        uasserted(ErrorCodes::SnapshotUnavailable,
+                  str::stream() << "Unable to read from a snapshot due to pending collection"
+                                   " catalog changes; please retry the operation.");
+    }
+
     DEV invariant(_isReady == _catalogIsReady(opCtx));
     return _isReady;
 }