MongoEngine Inside: the Detail of MongoDB & MongoEngine

1. when MongoEngine 1-1: use PyMongo or use MongoEngine? 2. from ORM to BSON 2-1: read MongoEngine source code to show how MongoEngine read from and .save() to MongoDB 2-2: how MongoEngine automatically dereference ObjectID as embedded document 2-3: .save() help us to write less bytes, but we also need to read less bytes how to pass needed fields use .only() or .exclude() how it affect .save() 3. race condition 3-1: introduce .objects().modify() and .objects().update() 3-2: how ORM design affects your implementation of atomic accessing: 3-2-1: store data in denormalization way (embedded documents): update atomically is trivial but data size is limited 3-2-2: store data in referencing way (independent documents): update atomically need brainstorming 4. index 4-1: index detail 4-1-1: difference between sortable index and hash (non sortable) index 4-1-2: no operation include upsert can ensure unique so if it is an unique field value, apply unique index 4-1-3: some details when indexing array field (including unique index for array field) 4-2: compound index 4-2-1: read query plan to understand what happened when query MongoDB 4-2-2: from 4-2-1 we can understand the gold indexing slogan: equal, sort, range 5. migration tips if can, use .update(multi=True) with some operation based on current value