====== MongoDB Quick Start, in Docker ======
These instructions configure a server instance named mongo-test, running MongoDB version 4.4.0 in a basic Ubuntu Bionic image. My host machine is running Ubuntu. I’m assuming you’ve already installed Docker. If not, you might want to check out [[:docker_linux|this article]].
You’ll probably need to sudo your docker commands.
===== Basics =====
Start a server instance:
docker run -p 27017:27017 --name mongo-test -d mongo:4.4.0-bionic
The port mapping (-p 27017:27017) is important. It allows you to connect to the running instance from your host machine.
A running instance can stopped with this:
docker stop mongo-test
And then started (or restarted) with this:
docker restart mongo-test
Open a bash shell in the running instance:
docker exec -it mongo-test bash
View MongoDB log files for the running instance:
docker logs mongo-test
===== Running Mongo Shell =====
You can run an interactive Mongo Shell a couple of ways.
==== Inside the running instance ====
First, open a bash shell inside the instance:
docker exec -it mongo-test bash
Then, run Mongo Shell:
mongo
==== From the host machine ====
First, install the MongoDB client tools:
sudo apt install mongodb-clients
Then, you can do this:
mongo --host localhost
===== Using Mongo Shell =====
==== List Databases ====
> show dbs
admin 0.000GB
config 0.000GB
local 0.000GB
==== Use Database ====
MongoDB doesn’t provide an explicit command for creating databases. A database will automatically be created the first time you try to use it (and add data).
Use a database called 'testdb':
> use testdb
switched to db testdb
In its simplest form, a database in MongoDB consists of two items:
- A **document**, which contains data, and,
- A **collection**, which is a container of documents.
A document is a data structure composed of field and value pairs. It’s a JSON object that MongoDB stores on disk in binary (BSON) format.
==== Drop Database ====
If you need to drop a database that’s already been created, you switch to it ('use'), then issue a dropDatabase command:
> show dbs
admin 0.000GB
config 0.000GB
local 0.000GB
testdb 0.000GB
> use testdb
switched to db testdb
> db.dropDatabase()
{ "dropped" : "testdb", "ok" : 1 }
> show dbs
admin 0.000GB
config 0.000GB
local 0.000GB
==== Add Data ====
Let’s add some data documents to testdb, in a collection called ‘people’:
> use testdb
switched to db testdb
> db.people.insert( {firstName: 'John', lastName: 'Smith'} )
WriteResult({ "nInserted" : 1 })
> db.people.insert( {firstName: 'Bob', lastName: 'Jones'} )
WriteResult({ "nInserted" : 1 })
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Bob", "lastName" : "Jones" }
The data in the insert commands is formatted as JSON, but quotes around key names are not required, and data can be single-quoted:
{
firstName: 'John',
lastName: 'Smith'
}
==== Update Data ====
To modify existing data, you pass two sets of data to update(): a filter, and an update action. The filter locates the document, and the update action specifies the data to modify.
In this example, we’ll change the “Bob Jones” record to “Robert Jones”:
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Bob", "lastName" : "Jones" }
> db.people.update({ firstName: "Bob", lastName: "Jones" }, { $set: {firstName: "Robert" } } )
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Robert", "lastName" : "Jones" }
==== Remove Data ====
To remove data, you pass a filter to remove(), specifying the document (or documents) you want to remove.
In this example, we’ll add a new document to the people collection, and then remove it.
> db.people.insert( { firstName: "To", lastName: "Remove" } )
WriteResult({ "nInserted" : 1 })
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Robert", "lastName" : "Jones" }
{ "_id" : ObjectId("5f4bf7595402b299ee512fd8"), "firstName" : "To", "lastName" : "Remove" }
> db.people.remove( { firstName: "To", lastName: "Remove"} )
WriteResult({ "nRemoved" : 1 })
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Robert", "lastName" : "Jones" }
==== Managing Collections ====
To see the collections in a database:
> use testdb
switched to db testdb
> show collections
people
You can also use getCollectionNames(), which returns results as BSON:
> db.getCollectionNames()
[ "people" ]
Add a collection explicitly with createCollection:
> show collections
people
> db.createCollection("things")
{ "ok" : 1 }
> show collections
people
things
Drop a collection:
> show collections
people
things
> db.things.drop()
true
> show collections
people
Count of documents in a collection:
> db.people.count()
2
==== Retrieving Data ====
We’ve already employed a simple find in our add/update/delete examples: db..find().
Find also accepts two optional parameters:
* Query filter: Describes how to filter the results, similar to a WHERE clause in SQL.
* Projection: Specifies which key/values from the document we want to see.
A find with no arguments retrieves up to the first 20 documents in a collection:
> db.people.find()
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Robert", "lastName" : "Jones" }
A filter with an exact match on one key looks like this:
> db.people.find( {firstName: "John"} )
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
Matching on multiple keys, similar to an AND in a SQL WHERE clause, looks like this:
> db.people.find(
... {
... $and: [
... { firstName: "John" },
... { lastName: "Smith" }
... ]
... });
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
MongoDB supports the following query comparison operators: $eq, $gt, $gte, $lt, $lte, $ne, $in, and $nin, along with the following logical operators: $or, $and, $not, and $nor. Regex is also supported.
Projections can be used to limit the keys returned. For example, here’s how to return just the last names:
> db.people.find( { }, { _id: 0, lastName: 1 } );
{ "lastName" : "Smith" }
{ "lastName" : "Jones" }
The numeric values indicate whether to include (1) or exclude (0) a given field. The _id field is always returned, unless specifically excluded.
Results can also be sorted:
> db.people.find( { }, { } ).sort( { lastName: 1 });
{ "_id" : ObjectId("5f4bc4e354e2c67896143098"), "firstName" : "Robert", "lastName" : "Jones" }
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
The numeric value controls whether to sort ascending (1) or descending (-1).
For large result sets, the number of results to return can be specified:
> db.people.find( { }, { } ).limit( 1 );
{ "_id" : ObjectId("5f4bc4dd54e2c67896143097"), "firstName" : "John", "lastName" : "Smith" }
===== MongoDB in .NET (C#) =====
Data in MongoDB can be accessed and manipulated in .NET (Standard and Core) applications using MongoDB.Driver. This is a simple introduction to connecting to MongoDB, retrieving data, and displaying it.
Create a .NET Core console application:
dotnet new console -o DotMongo
Add a reference to MongoDB.Driver:
cd DotMongo
dotnet add package MongoDB.Driver --version 2.11.1
Open Program.cs in your editor of choice, and replace the contents with this:
using System;
using MongoDB.Driver;
using MongoDB.Bson;
namespace DotMongo
{
class Program
{
static void Main(string[] args)
{
try
{
var databaseName = "testdb";
// Get database reference.
var mongoDatabase = GetDatabaseReference("localhost", 27017, databaseName);
Console.WriteLine($"Connected to database {databaseName}");
// Get a reference to the "people" collection inside testdb.
var collection = mongoDatabase.GetCollection("people");
// We're retrieving all documents in the collection,
// but we still need an empty filter.
var filter = new BsonDocument();
var count = 0;
// Open a cursor with all the matching documents.
using (var cursor = collection.FindSync(filter))
{
// Iterate through the cursor
while (cursor.MoveNext())
{
// Get documents at the current cursor location.
var batch = cursor.Current;
foreach (var document in batch)
{
// Get values from the current document, then display them.
var firstName = document.GetElement("firstName").Value.ToString();
var lastName = document.GetElement("lastName").Value.ToString();
Console.WriteLine($"Full name: {firstName} {lastName}");
count++;
}
}
}
Console.WriteLine($"Total records: {count}");
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
public static IMongoDatabase GetDatabaseReference(string hostName, int portNumber, string databaseName)
{
string connectionString = $"mongodb://{hostName}:{portNumber}";
// Connect to MongoDB
var mongoClient = new MongoClient(connectionString);
// Get a reference to the specified database
var mongoDatabase = mongoClient.GetDatabase(databaseName);
return mongoDatabase;
}
}
}
Run the application:
dotnet run
You should see output that looks like this:
Connected to database testdb
Full name: John Smith
Full name: Robert Jones
Total records: 2
You can find the full project [[https://github.com/jfcarr/mongodb-dotnet-quick-start|here]].
===== Learn More =====
[[https://www.mongodb.com/|MongoDB home page]]
[[https://github.com/mongodb/mongo|MongoDB on GitHub]]
[[https://hub.docker.com/_/mongo|MongoDB on Docker Hub]]
[[https://www.syncfusion.com/ebooks/mongodb_3_succinctly|MongoDB 3 Succinctly]]
{{tag>database docker}}