SERVER-40169 OplogApplier::getNextApplierBatch() processes system.views oplog entries individually

This applies changes from commit f78e580dad60fa6ece39f34b3dcfc3ed95b85414.

2 files changed, 19 insertions, 2 deletions

diff --git a/src/mongo/db/repl/oplog_applier.cpp b/src/mongo/db/repl/oplog_applier.cpp
index a3c4e1953f8..0602c4d261f 100644
--- a/src/mongo/db/repl/oplog_applier.cpp
+++ b/src/mongo/db/repl/oplog_applier.cpp
@@ -152,8 +152,13 @@ StatusWith<OplogApplier::Operations> OplogApplier::getNextApplierBatch(
         // Commands must be processed one at a time. The only exception to this is applyOps because
         // applyOps oplog entries are effectively containers for CRUD operations. Therefore, it is
         // safe to batch applyOps commands with CRUD operations when reading from the oplog buffer.
-        if (entry.isCommand() && (entry.getCommandType() != OplogEntry::CommandType::kApplyOps ||
-                                  entry.shouldPrepare())) {
+        //
+        // Oplog entries on 'system.views' should also be processed one at a time. View catalog
+        // immediately reflects changes for each oplog entry so we can see inconsistent view catalog
+        // if multiple oplog entries on 'system.views' are being applied out of the original order.
+        if ((entry.isCommand() && (entry.getCommandType() != OplogEntry::CommandType::kApplyOps ||
+                                   entry.shouldPrepare())) ||
+            entry.getNss().isSystemDotViews()) {
             if (ops.empty()) {
                 // Apply commands one-at-a-time.
                 ops.push_back(std::move(entry));
diff --git a/src/mongo/db/repl/oplog_applier_test.cpp b/src/mongo/db/repl/oplog_applier_test.cpp
index d5bd62948e0..1ebf834a2b5 100644
--- a/src/mongo/db/repl/oplog_applier_test.cpp
+++ b/src/mongo/db/repl/oplog_applier_test.cpp
@@ -199,6 +199,18 @@ TEST_F(OplogApplierTest, GetNextApplierBatchGroupsUnpreparedApplyOpsOpWithOtherO
     ASSERT_EQUALS(srcOps[1], batch[1]);
 }
 
+TEST_F(OplogApplierTest, GetNextApplierBatchReturnsSystemDotViewsOpInOwnBatch) {
+    OplogApplier::Operations srcOps;
+    srcOps.push_back(makeInsertOplogEntry(
+        1, NamespaceString(dbName, NamespaceString::kSystemDotViewsCollectionName)));
+    srcOps.push_back(makeInsertOplogEntry(2, NamespaceString(dbName, "bar")));
+    _applier->enqueue(_opCtx.get(), srcOps.cbegin(), srcOps.cend());
+
+    auto batch = unittest::assertGet(_applier->getNextApplierBatch(_opCtx.get(), _limits));
+    ASSERT_EQUALS(1U, batch.size()) << toString(batch);
+    ASSERT_EQUALS(srcOps[0], batch[0]);
+}
+
 }  // namespace
 }  // namespace repl
 }  // namespace mongo