# MongoDB

## Tutorials

Name | Description
:------|:------:
[Guru99 MongoDB Tutorial](https://www.guru99.com/what-is-mongodb.html) | MongoDB Tutorial
[Tutorialspoint Tutorial](https://www.tutorialspoint.com/mongodb) | MongoDB Tutorial

## Authentication and Authorization

Name | Description
:------|:------:
[Tutorial User Administration Without You Integrating LDAP with MongoDB](https://www.youtube.com/watch?v=ky8OKWPCZXs&ab_channel=MongoDB) | Full explanation on Mongo and LDAP integration

## Cheat Sheet

### Mongo Shell

#### General

* DB stats: `db.stats()`
* Switch to a DB: `use DB_NAME`
* Show collections: `show collections`
* Show all the document in a collection: `db.COLLECTION_NAME.find({})`
* Count the number of documents in a collection: `db.COLLECTION_NAME.count()`
* Remove all the documents from a collection: `db.COLLECTION_NAME.remove({})`
* Remove field from all documents: `db.COLLECTION_NAME.update({}, {$unset: { FIELD_NAME: ""}}, {multi:true})` 
* Rename field: ```db.hosts.updateMany( {}, { $rename: { "CURRENT_FIELD_NAME": "NEW_FIELD_NAME" } } )```

#### Mongoexport 

* Export Mongo DB collection to a JSON file: `mongoexport --db=DB_NAME --collection=COLLECTION_NAME --out=data.json`
* Export specific fields from a Mongo DB collection to a  JSON file: `mongoexport --db=DB_NAME  --fields=FIELD_NAME,FIELD_NAME2 --collection=COLLECTION_NAME --out=data.json`

#### Aggregations

* Count the number of documents: `db.accounts.aggregate([ { "$count": "number of documents" }])`
* Show only the sub element 'attachment_uuids': `db.accounts.aggregate( [ {$project: {"hosts.attachment_uuids": 1, _id:0}} ] )`

#### Users

* Display users:

```
use admin
db.getUsers()
```

* Create administrative user

```
use admin
db.createUser({user: "admin", pwd: "some_password", roles: ["root"]})
```

* Authentice: `db.auth(USERNAME, PASSWORD)`

#### Roles

* Display roles

```
use admin
db.getRoles()
```

* Drop/Remove role: `db.dropRole("NAME_OF_THE_ROLE")`

#### LDAP

* Mongo Conf LDAP configuration

```
security:
  # authorization: "enabled"
  ldap:
    servers: 'some.ldap.server.com'
    userToDNMapping:
         '[
            {
               match: "(.+)",
               ldapQuery: "DC=X,DC=com??sub?(uid={0})"
            }
         ]'
    authz:
         queryTemplate: "{USER}?memberOf?base"
setParameter:
  authenticationMechanisms: 'PLAIN,SCRAM-SHA-1'
```

* Create role where the LDAP group "unicorns" has permissions to only run 'find' on "hosts" collection in 'test' db:

```
db.createRole({role:"cn=unicorns,ou=groups,dc=X,dc=com", privileges: [{ resource: {db: "", collection: "hosts"}, actions: ["find"]}], roles: [{ role: "read", db: "test"}]})
```

* Drop/Remove role from the previous example: `db.dropRole("cn=unicorns,ou=groups,dc=X,dc=com")`

### Mongo Python

* Add new element to an arrray only if it doesn't exists already

```
mongo_client.update(
       { "account_number": account_num },
       { "$addToSet": { "hosts": {'hostname': hostname} } }
    )
```

* Add a new element to an array in sub-document (if it doesn't exists already):

```
mongo_client.update_one(
       { "account_number": account_num, "hosts.hostname": hostname },
       { "$addToSet": { "hosts.$.attachment_uuids": attachment_uuid } }
    )
```

* Add all the elements in an array to an array in document (This is not about adding the array as it is but adding the elements of it):

```
mongo_client.update_one(
    {'_id': 1},
    {'$addToSet': {'some_list': { '$each': [1, 2, 3]} }}, upsert=True)
```