MongoDB - 在同一个集合上有不同文档的缺点？

Question

What are the downsides of storing completely different documents on the same collection of MongoDB?

Unlike others questions, the documents I'm referring to are not related (like parent-child).

The motivator here is cost-reduction. Azure CosmosDB Mongo API charges and scalability are per-collection.

Answer 1

• The size of the collection will get a lot bigger a lot faster.
• Speed of queries could be impacted as you'll have to scan more documents than required (could maybe use sparse indexes)
• Index sizes will be a lot bigger and longer to scan
• You'll need to store a discriminator with the documents so you can tell what type one document is compared to another.

If the documents are not related at all, I'd store them in completely separate collections.