Today I Learned About Mongodb

Intro

I started building using NoSQL database and preferred MongoDB. Here are my solutions to some problems I ocurred while I build stuff with it.

Solutions

query without Object ID

If otherwise defined, MongoDB has default primary key on each document after insertion.

![[mongodb-objectid.png]]

This can create issues while querying from an api service as ORM object on non-specific queries. It is possible to exclude it using {'_id': 0}

example query:

result = collection.find_one(
	{
		'scale': 'global', 
		 'region': 'south america',
		  'domain': 'nations' 
	  }, 
	  {'_id': 0}
	)

sorting historical query results

Historical queries are not returned in sorted order by default. To do asc/desc sorting on specific key you can:

db["collection_name"].find({'scale': 'global'}).sort('created_at', -1)

Sort orders are:

  • -1 = Ascending
  • 1 = Descending

using python reserved keyword as document key

Some variable/key names are reserved on Python, such as “class”. In order to create an ORM model representing documents with “class” key, you should pre/postfix a minor symbol to it: “class_” on the model.

You convert back to its key valueon ORM model using pydantic schemas.

class User(BaseModel):
    id: int
    Class_: bool

    class Config:
        fields = {
            'class_': 'class'
        }

details

databasenosqlmongodbnotes