Workaround for MongoDB to support PivotTable

Per the document there is a workaround for the limitation that PivotTable is not supported with MongoDB as database.

The workaround is to build a Question (or Model?) to get the raw data first and have that Question (as opposed to the MongoDB tables) as a data source for the Question you want to create Pivot Table. It's great to know there is a workaround for the MongoDB limitation but I am a bit confused here.

My questions:

  1. In the document, it says MongoDB currently doesnt' support Join operation but in the example below Joins are used to create the raw-data-collection Question. If Join is not supported with MongoDB why could Joins are used here in the example?

  2. If this workaround is effective, can we safetly conclude that Pivot Table can be supported indirectly with MongoDB, despite with a hassle that user has to build the raw-data-collection Questions first, which is totally fine from my perspective because the additional effort is not comparable to the huge benefit Metabase provides.

Mongo has limited support in Metabase compared to other database types.

I've solved it using a tool to migrate MongoDB data to Postgres, I've found a great old tool that works perfect to do that (Working on MongoDB 3.6.14). It keep all data synced watching MongoDB operation logs.