how to check if the document id is exist in case of dynamically created models/collections?

[xmarya]

I want to create a middleware function to check if the document_Id exists and it's not wrong using Model.exist({_id: id}) or such a query, so the API throws an error.

However, the problem is my models/collections are created dynamically:

• the reviews would be: Reviews-product-${productId} OR Reviews-store-${storeId}

let's assume the scenario of passing a userId to create a new dynamic model for product reviews. My code right now accepts that userId and creates a model/collection named Reviews-product-${userId} based on it because it lacks the validation step.

here are the functions that create the dynamic models/collections:

function createDynamicModel<T extends mongoose.Document>(modelName: string, schema: mongoose.Schema, collection: string): mongoose.Model<T> {
      try {
    
        let dynamicModel;
        // STEP 1) Double guard — Prevents actual Mongoose runtime error if the previous guard fall out of sync
        if (mongoose.connection.models[modelName]) dynamicModel = mongoose.connection.models[modelName] as mongoose.Model<T>;
        else dynamicModel = mongoose.connection.model<T, mongoose.Model<T>>(modelName, schema, collection);
    
        // STEP 2)Always make sure the cache is up-to-date
        lruCache.set(modelName, dynamicModel);
        console.log("inside createDynamicModel", dynamicModel);
        
        return dynamicModel;
      } catch (error) {
        console.log((error as AppError).message);
        throw new AppError(500, "couldn't create dynamic model");
      }
    }
    
    export function getDynamicModel<T extends mongoose.Document>(model: DynamicModel, modelId: string): mongoose.Model<T> {
      // only for getting reviews that are related to stores and products
    
      // STEP 1) get necessary data for dynamic model:
      const { modelName, schema, collection } = getDynamicModelData(model, modelId);
    
      if (!schema) throw new AppError(500, `Schema for model ${model} not found.`);
    
      // STEP 2) create a new modelName if it doesn't exist in the cache or in the mongoose.model:
      if (!lruCache.has(modelName) || !mongoose.connection.modelNames().includes(modelName)) createDynamicModel(modelName, schema, collection);
        
      const dynamicModel = lruCache.get(modelName) as mongoose.Model<T>;
      return dynamicModel;
    }

TL;DR when getDynamicModel is called, it is going to check if the modelName exists, if doesn't, it would create a new model. Nothing prevents a model with a wrong or non-existing id form being created

Making my Store model, which is not dynamic- know its product means keeping a reference to the products' ids inside it but then the whole logic of creating the models/collections dynamically has nonsense I've been trying to solve this since yesterday.

Your help would be highly appreciated.

[vkarpov15]

First, I strongly advise against creating a separate review collection per product or per store. I recommend having a single Reviews-product model and index on productId.

That being said, with your current setup, what prevents you from checking if a given userId exists using User.exists({ _id: userId }) in your getDynamicModel() call?

[xmarya]

I'd like to hear more about why you're against the current implementation of creating separate collections, I did that to prepare for future scaling. Something like reviews can easily get huge, so I decided to go with this path to keep the performance at its best.
Regarding the actual problem I've faced, I managed to solve it.

[vkarpov15]

For scaling, there isn't any benefit to having separate user collections vs having one user collection with indexes AFAIK. And MongoDB recommends limiting the number of collections in your database for performance reasons.