SERVER-27406 Reduce DocumentSourceCursor batch size from 16MB to 4MB

4 files changed, 6 insertions, 9 deletions

diff --git a/jstests/concurrency/fsm_workloads/kill_multicollection_aggregation.js b/jstests/concurrency/fsm_workloads/kill_multicollection_aggregation.js
index ba38bdfe94a..f15dbb05432 100644
--- a/jstests/concurrency/fsm_workloads/kill_multicollection_aggregation.js
+++ b/jstests/concurrency/fsm_workloads/kill_multicollection_aggregation.js
@@ -280,8 +280,9 @@ var $config = (function() {
 
     function teardown(db, collName, cluster) {
         cluster.executeOnMongodNodes(function lowerDocumentSourceCursorBatchSize(db) {
+            // Restore DocumentSourceCursor batch size to the default.
             assertAlways.commandWorked(db.adminCommand(
-                {setParameter: 1, internalDocumentSourceCursorBatchSizeBytes: 16 * 1024 * 1024}));
+                {setParameter: 1, internalDocumentSourceCursorBatchSizeBytes: 4 * 1024 * 1024}));
         });
 
         var myDB = db.getSiblingDB(this.uniqueDBName);
diff --git a/src/mongo/db/pipeline/document_source_cursor.cpp b/src/mongo/db/pipeline/document_source_cursor.cpp
index 61fd276c2ec..b8bacacf015 100644
--- a/src/mongo/db/pipeline/document_source_cursor.cpp
+++ b/src/mongo/db/pipeline/document_source_cursor.cpp
@@ -46,14 +46,6 @@ using boost::intrusive_ptr;
 using std::shared_ptr;
 using std::string;
 
-namespace {
-
-MONGO_EXPORT_SERVER_PARAMETER(internalDocumentSourceCursorBatchSizeBytes,
-                              int,
-                              FindCommon::kMaxBytesToReturnToClientAtOnce);
-
-}  // namespace
-
 const char* DocumentSourceCursor::getSourceName() const {
     return "$cursor";
 }
diff --git a/src/mongo/db/query/query_knobs.cpp b/src/mongo/db/query/query_knobs.cpp
index a05a1c073d8..496f69c5c47 100644
--- a/src/mongo/db/query/query_knobs.cpp
+++ b/src/mongo/db/query/query_knobs.cpp
@@ -72,4 +72,6 @@ MONGO_EXPORT_SERVER_PARAMETER(internalInsertMaxBatchSize,
                               int,
                               internalQueryExecYieldIterations / 2);
 
+MONGO_EXPORT_SERVER_PARAMETER(internalDocumentSourceCursorBatchSizeBytes, int, 4 * 1024 * 1024);
+
 }  // namespace mongo
diff --git a/src/mongo/db/query/query_knobs.h b/src/mongo/db/query/query_knobs.h
index 4b3a0760c65..67bff82bb1e 100644
--- a/src/mongo/db/query/query_knobs.h
+++ b/src/mongo/db/query/query_knobs.h
@@ -113,4 +113,6 @@ extern std::atomic<int> internalQueryFacetBufferSizeBytes;  // NOLINT
 
 extern std::atomic<int> internalInsertMaxBatchSize;  // NOLINT
 
+extern std::atomic<int> internalDocumentSourceCursorBatchSizeBytes;  // NOLINT
+
 }  // namespace mongo