Changing a schema path using schema.path significantly affects performance

[mcat95]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.10.0

Node.js version

v18.19.0

MongoDB server version

8.0.4

Typescript version (if applicable)

No response

Description

When using schema.path to add a SingleNested type to a preexisting schema, adds the new SingleNested children to the childSchemas schema property, regarding of whether it was already in the array. This affects save() operations on large documents, with deeply nested documents.

Multiple calls to the path method make the issue exponentially worse.

We've found that calling _gatherChildSchemas() is an effective workaround and fixes the issue.

Steps to Reproduce

const mongoose = require('mongoose');
const crypto   = require('crypto');

const RecursiveSchema = new mongoose.Schema({
  data: String,
});

const s = [ RecursiveSchema ];
RecursiveSchema.path('nested', s);

// If you comment the following line the issue goes away
RecursiveSchema.path('nested', s);

// If you uncomment the following lines the issue gets even worse
//RecursiveSchema.path('nested', s);
//RecursiveSchema.path('nested', s);

// Uncoment for a workaround
//RecursiveSchema._gatherChildSchemas();

const generateRecursiveDocument = (depth, curr = 0) => {
  return {
    name: `Document of depth ${curr}`,
    nested: depth > 0 ? new Array(3).fill().map(() => generateRecursiveDocument(depth-1, curr+1)) : [],
    data: crypto.randomBytes(128).toString('hex'),
  };
}

const main = async () => {
  console.log(mongoose.version)
  await mongoose.connect('mongodb://localhost/mongoose-test');
  const model = new mongoose.model('Recursive', RecursiveSchema);
  const data = generateRecursiveDocument(6);
  const doc = new model(data)
  console.time('Save time');
  await doc.save();
  console.timeEnd('Save time');
};

main().then(process.exit);

Expected Behavior

The save operation should not take more than 100ms, which is the case when you only call the path function once.

[mcat95]

Hello @vkarpov15,

Thanks for taking a look into this performance issue. We've found a very similar related issue and reported it on #15255

Thanks!