Hands-on session: Document Data Store (NoSQL)

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# MongoDB (Document Data Store)
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1. Let's retrieve the Docker image with pre-installed MongoDB
	(we use the official container)

	docker pull mongo

2. We can now create an isolated network with a MongoDB server
	docker network create mongonet
	docker run -i -t -p 27017:27017 --name mongo_server --network=mongonet mongo:latest /usr/bin/mongod --bind_ip_all


3. In another shell we can create a Mongo client, connected to the same network
	docker run -i -t --name mongo_cli --network=mongonet mongo:latest /bin/bash

4. On the client, we open the command line interface "mongosh", specifying the address of the server
	mongosh mongo_server:27017

5. We are ready to use MongoDB. We consider as use case an content management system, which needs to
	manage posts, images, videos, and so on, each with its own specific attributes; for example:

	{ name : "hello world", type : "post", size : 250, comments : ["c1", "c2"] }

	{ name : "sunny day", type : "image", size : 3, url : "abc" }

	{ name : "tutorial", type : "video", length : 125, path : "/video.flv", metadata : {quality : "480p", color : "b/n", private : false } }


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Basic operations
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# Create and switch to a new database named "cms"
	use cms

# Insert in a collection named "cms" several documents (a post, an image, and a video)

	db.cms.insert({ name : "hello world", type : "post", size : 250, comments : ["c1", "c2"] } )
	db.cms.insert({ name : "sunny day", type : "image", size : 300, url : "abc" })
	db.cms.insert({ name : "tutorial", type : "video", length : 125, path : "/video.flv", metadata : {quality : "480p", color : "b/n", private : false } })

# Querying the database to find documents
	# General syntax: db.cms.find({ <criteria> })
	db.cms.find()

	db.cms.find({type : "image" } )
	db.cms.insert({ name : "mycms-logo", type : "image", size : 3, url : "cms-logo.jpg" })
	db.cms.find({type : "image" } )

	db.cms.find( {size : { $gt : 100 } } )
	db.cms.find( {size : { $lt : 100 } } )

	db.cms.find({ length : { $exists: true } } )
	db.cms.find({ comments  : { $exists: true } } )
	db.cms.find({ "comments.2"  : { $exists: true } } )
	db.cms.find({ "comments.1"  : { $exists: true } } )

	db.cms.find({ "metadata.quality" : { $exists: true } } )
	db.cms.find({ "metadata.quality" : "360p" } )
	db.cms.find({ "metadata.quality" : "480p" } )
	db.cms.find({ "metadata.private" : false } )

	db.cms.findOne({ comments  : { $exists: true } } )
	db.cms.findOne({ comments  : { $exists: true } } ).comments[1]


# A slightly more complex query, that combines multiple conditions in a logical AND or OR condition:
AND:
	db.cms.find( {size : { $gt : 100 } , type : "image" } )

OR:
	db.cms.find( { $or : [ { size : { $gt : 100 } } , {  type : "image" } ] } )

# Sort results in ascending (value = 1) or descending order (value = -1)
	# General syntax: .sort({ <criteria> })

	db.cms.find().sort( { name : 1 } )
	db.cms.find({type : "image" }).sort( { name : -1 } )
	db.cms.find().sort( { nonexistingfield : 1 } )


# Update a document: there are several way to update a document; 
#  for example we can simply update a subset of fields using the operator $set:
	# General syntax: .updateOne({ <criteria> }, { <update> }, )

	db.cms.updateOne({ "name" : "Canon EOS 750D" },  { $set: { "address.street": "East 31st Street" } } )

# Update a document: the previous command changes only a single document (the first occurrence);
#  if the update should be performed on multiple occurrences, them .updateMany() function should be used. 
#  This corresponds to using the .update({condition}, {set}, {multi: true}) command, which is deprecated nowadays.
	db.cms.updateMany({ "name" : "mycms-logo" },  { $set: { "metadata.quality": "hd" } } )
	db.cms.find({name : "mycms-logo"})
	db.cms.find({type : "image"})
	db.cms.updateMany({ type : "image" },  { $set: { "metadata.author": "myname" } } )
	# equivalent to the old command: 
	# db.cms.update({ type : "image" },  { $set: { "metadata.author": "myname" } } , {multi: true} )
	db.cms.find({type : "image"})

# Update a document: how to add a new element to an array (using the operator $push):
	db.cms.find({ type : "post" } )
	db.cms.updateOne({ name : "hello world" },  { $push: { "comments": "a new comment" } } )
	db.cms.updateMany({ name : "hello world" },  { $push: { "comments": "a second new comment" } } )
	db.cms.find({ type : "post" } )

# Replace a document: override the whole document
	# General syntax: .replaceOne({ <criteria> }, { <replacement> }, )

	db.cms.find()
	db.cms.replaceOne({ name : "mycms-logo" },  { author : "myname" } )
	db.cms.find()


# Remove documents. By default .remove() removes all the documents that match the document fields passed as argument. If a single delete should be performed, we need to use the parameter "justOne".
	db.cms.remove( { type : "video" } )
	db.cms.remove( { author : "myname" } , { justOne: true } )

	# the following removes all documents
	db.cms.remove( { } )


# We can also drop the whole collection (together with its documents)
	db.cms.drop()