perf(document): avoid unnecessary set creation in $__reset() re: #14719

Author: vkarpov15

lib/document.js

@@ -3470,31 +3470,33 @@ Document.prototype.$__reset = function reset() {
   let _this = this;
 
   // Skip for subdocuments
-  const subdocs = this.$parent() === this ? this.$getAllSubdocs() : [];
-  const resetArrays = new Set();
-  for (const subdoc of subdocs) {
-    const fullPathWithIndexes = subdoc.$__fullPathWithIndexes();
-    subdoc.$__reset();
-    if (this.isModified(fullPathWithIndexes) || isParentInit(fullPathWithIndexes)) {
-      if (subdoc.$isDocumentArrayElement) {
-        resetArrays.add(subdoc.parentArray());
-      } else {
-        const parent = subdoc.$parent();
-        if (parent === this) {
-          this.$__.activePaths.clearPath(subdoc.$basePath);
-        } else if (parent != null && parent.$isSubdocument) {
-          // If map path underneath subdocument, may end up with a case where
-          // map path is modified but parent still needs to be reset. See gh-10295
-          parent.$__reset();
+  const subdocs = !this.$isSubdocument ? this.$getAllSubdocs() : null;
+  if (subdocs && subdocs.length > 0) {
+    const resetArrays = new Set();
+    for (const subdoc of subdocs) {
+      const fullPathWithIndexes = subdoc.$__fullPathWithIndexes();
+      subdoc.$__reset();
+      if (this.isModified(fullPathWithIndexes) || isParentInit(fullPathWithIndexes)) {
+        if (subdoc.$isDocumentArrayElement) {
+          resetArrays.add(subdoc.parentArray());
+        } else {
+          const parent = subdoc.$parent();
+          if (parent === this) {
+            this.$__.activePaths.clearPath(subdoc.$basePath);
+          } else if (parent != null && parent.$isSubdocument) {
+            // If map path underneath subdocument, may end up with a case where
+            // map path is modified but parent still needs to be reset. See gh-10295
+            parent.$__reset();
+          }
         }
       }
     }
-  }
 
-  for (const array of resetArrays) {
-    this.$__.activePaths.clearPath(array.$path());
-    array[arrayAtomicsBackupSymbol] = array[arrayAtomicsSymbol];
-    array[arrayAtomicsSymbol] = {};
+    for (const array of resetArrays) {
+      this.$__.activePaths.clearPath(array.$path());
+      array[arrayAtomicsBackupSymbol] = array[arrayAtomicsSymbol];
+      array[arrayAtomicsSymbol] = {};
+    }
   }
 
   function isParentInit(path) {

lib/model.js

@@ -3209,6 +3209,7 @@ Model.$__insertMany = function(arr, options, callback) {
           return callback(err);
         }
       }
+
       if (options.session != null) {
         doc.$session(options.session);
       }