====== MongoDB Cheatsheet ======

=== Introduction ===
MongoDB is a NoSQL, document-oriented database that stores data in flexible, JSON-like documents. It is designed for scalability, high availability, and developer ease of use.

=== Key Concepts ===
  * **Document**: The basic unit of data in MongoDB, stored in BSON (binary JSON).
  * **Collection**: A group of documents, similar to a table in relational databases.
  * **Database**: A container for collections.
  * **Field**: A key-value pair in a document, similar to a column in relational databases.
  * **Replica Set**: A group of MongoDB servers that maintain the same data, providing redundancy and high availability.

=== Basic Commands ===

  * **Show Databases**:
    ```
    show dbs
    ```
  * **Switch to Database**:
    ```
    use <database_name>
    ```
  * **Show Collections**:
    ```
    show collections
    ```
  * **Insert a Document**:
    ```
    db.collection.insert({ "key": "value" })
    ```
  * **Find Documents**:
    ```
    db.collection.find()
    ```
  * **Find with Filter**:
    ```
    db.collection.find({ "key": "value" })
    ```
  * **Update a Document**:
    ```
    db.collection.update({ "key": "value" }, { $set: { "key": "new_value" } })
    ```
  * **Delete a Document**:
    ```
    db.collection.remove({ "key": "value" })
    ```

=== Aggregation ===
MongoDB provides aggregation operations for advanced data processing.
  * **Simple Aggregation**:
    ```
    db.collection.aggregate([{ $match: { "key": "value" } }])
    ```
  * **Grouping Data**:
    ```
    db.collection.aggregate([
      { $group: { _id: "$field", total: { $sum: 1 } } }
    ])
    ```

=== Indexes ===
Indexes improve query performance.
  * **Create an Index**:
    ```
    db.collection.createIndex({ "key": 1 })
    ```
  * **Drop an Index**:
    ```
    db.collection.dropIndex({ "key": 1 })
    ```

=== Replica Sets ===
To enable high availability:
  * **Initiate a Replica Set**:
    ```
    rs.initiate()
    ```
  * **Add a Member**:
    ```
    rs.add("hostname:port")
    ```

=== Backup and Restore ===
  * **Backup a Database**:
    ```
    mongodump --db <database_name> --out <backup_directory>
    ```
  * **Restore a Dat