Parse: Prepare DB migration

[GerberI]

To migrate the DB to be compatible with parse, some research has to be done.

Object ids

Parse-server uses/requires type string for primary keys (attribute _id) in collections but our mongo db collections are using type ObjectId. ObjectIds can be auto created, string ids not.

Read: ObjectId in MongoDB

• What exact id format to use? Parse server, mongoose or mongoDB format?
• Is there a possibility to auto generate string ids via mongoose, mongoDB driver or parse server?
• Are migrated ids compatible with parse-server and mongoose?
• Does the parse server or mongoDB check for uniqueness of keys?

"created" and "updated" fields

createdAt and updatedAt fields should be renamed to _created_at and _updated_at because the parse-server uses these fields.

• Is the current date format compatible with parse server?

Revision keys

Avoid/Rename field names starting with '_' except the ones mentioned above. Currently only '__v' is used (auto created by mongoose as revision counter).

Read: versionKey in mongoose

• Are the revision keys necessary for mongoose or can they be disabled/removed?

Indexing

• Check if mongoose indexing is compatible with parse-server.
• How and when are the indices created/updated by mongoose, parse server and mongoDB?
• Perhaps indexing can be disabled (we have small databases).

[birgitlewicki]

Results of this ticket are described at https://gitlab.bfr.berlin/devs43/common/parse-integration/-/wikis/Using-parse-server-with-existing-mongo-db-collections