Misskey v11 coming soon (Patreon)

Goodbye MongoDB.

Misskey has abandoned MongoDB and decided to use PostgreSQL.

I am currently working on it. This is a major change and takes time.

## Why Misskey Adopts PostgreSQL:

* Most of Misskey's data has a fixed schema, not schemaless. Also, the data is relational. Thus, a relational database makes more sense.

* Misskey does not perform processing that can only be realized with MongoDB.

* Relational database-specific features (eg CASCADE DELETE) simplify the implementation of some processes.

* MongoDB had operational problems such as difficulty in backing up.

* MongoDB is not a major compared to PostgreSQL. It means less documentation and tools for installation, which makes the installation of Misskey difficult.

* Type conversion of ObjectID is troublesome.

This is a daunting task. When this is complete, Misskey will be v11. looking forward to!