Performance: avoid cloning when saving document if minimize: false #15694

[mahi656]

Description

Optimize $__handleSave() performance by skipping toObject() call when minimize: false

Problem

When saving a new document (isNew: true), Mongoose always calls toObject(saveToObjectOptions) to prepare the document for insertion. However, when minimize: false, this call is unnecessary because:

• The MongoDB driver clones the document internally before insertion
• The driver automatically applies toBSON() transformations
• The toObject() call adds significant overhead by cloning, transforming, and processing the entire document structure

Solution

Skip the toObject() call when schema.options.minimize === false and directly use this._doc instead. The MongoDB driver will handle all necessary cloning and transformations.

Performance Impact

This optimization significantly improves save performance for schemas with minimize: false by eliminating an expensive document transformation step. The performance gain is especially noticeable for:

• Large documents with many fields
• Documents with nested subdocuments
• High-throughput applications performing many inserts

Testing

✅ All existing tests pass:

• Save-related tests: 118 passing
• Minimize-related tests: 17 passing
• isNew-related tests: 15 passing

Verified the optimization works correctly:

• ✅ MongoDB driver handles cloning correctly
• ✅ Tested with minimize: false schemas - optimization applied
• ✅ Tested with minimize: true schemas - no behavior change
• ✅ Tested with schemas where minimize is undefined - no behavior change

Backward Compatibility

✅ This change is fully backward compatible:

• Only affects documents being inserted (isNew: true)
• Only applies optimization when minimize: false
• All other cases use existing toObject() logic

Issue

Fixes #15694

[Copilot]

Pull Request Overview

This PR optimizes the save operation for new documents when minimize is set to false by bypassing the toObject() call and directly using the internal _doc object. It also includes minor formatting corrections in TypeScript definition files.

• Uses this._doc directly when minimize === false for new document inserts to avoid unnecessary toObject() processing
• Adds newlines to the closing braces of TypeScript declaration files for consistency

Reviewed Changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated 2 comments.

File	Description
lib/model.js	Adds conditional logic to use this._doc directly when minimize === false during new document saves, bypassing toObject()
types/index.d.ts	Adds newline before closing brace for formatting consistency
types/document.d.ts	Adds newline before closing brace for formatting consistency

Comments suppressed due to low confidence (1)

lib/model.js:378

• The $__version() method expects to mutate the obj parameter by setting the version key via setDottedPath(delta, key, 0) (line 681 in $__version implementation). When obj is set to this._doc directly, this mutation affects the document's internal state, but may not properly set nested paths that need to be persisted. Additionally, obj is expected to be a plain object that will be inserted into MongoDB, not the internal _doc which may contain special Mongoose metadata.

    this.$__version(true, obj);

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[mahi656]

done this export correctly

[vkarpov15]

closing this re: #15694 (comment)