MongoDB For C++ Developers

MongoDB For C++
Developers
{ author: “Ynon Perek” }

Saturday, February 2, 13

Whoami

Ynon Perek

http://ynonperek.com

ynon@ynonperek.com


Agenda

Mongo Is Awesome

CRUD Operations

The Driver

Coding Time


Mongo Is Awesome

Data Store for
JSON Objects


Mongo Is Awesome

Data Store for
JSON Objects

{
“Name” : “Rose Tyler”
}


JSON Objects

A JSON Object is a
collection of key/
value pairs {
"name" : "Rose Tyler",
Keys are simple "race" : "Human",
strings "body parts" : [ "head", "legs"]
}
Values can be:
Numbers, Strings,
Arrays, Other
Objects, and more


It’s A Document Oriented Data
Store


It don’t do joins


It don’t do transactions


Keeping It Simple

Document Oriented

No Transactions

No Joins


Application Architecture

APP DB


Application Architecture

DB

APP DB

DB


What Can Mongo Do For You

Create and store objects

Arrange them in collections

Retrieve them later


Q&A


CRUD Operations
Create, Read, Update and Destroy Data


Mongo CRUD

Create is called insert

Read is called find

Update is called update

Destroy is called remove


Mongo CRUD

From a developer’s perspective, MongoDB operations are
the same through the driver and through the console

In both cases, operations look like function calls or
method invocations

We’ll use mongo shell for the rest of this chapter


Inserting Data

Use the command insert or save to insert a new object

db.collection.insert( obj );

db.collection.insert( array );


Inserting Data

Inserting to a new collection creates the collection

Inserting an object with an _id key, it is used as the
object’s id (and must be unique).


Demo: Insert


Reading Data

find and findOne perform read operations

Both take a query

find returns a cursor

findOne returns an object Optional: Fields to
fetch

db.collection.find( <query>, <projection> )


Query Document

An empty (or missing) query document returns
everything

db.collection.find({})

db.collection.find()


Query Document

Each key/value pair in the query document imposes a
condition on the results (objects that match).

db.movies.find({ “genre” : “indie” });

db.books.find({“pages” : { “$gt” : 100 }});


Query Document

Query Object

Each key/value pair in the query document imposes a
condition on the results (objects that match).

db.movies.find({ “genre” : “indie” });

db.books.find({“pages” : { “$gt” : 100 }});


Query Document

A compound query means a logical AND on the
conditions.

db.inventory.find(
{
“type” : “snacks”,
“available” : { “$lt” : 10 }
});


Quiz: What Is Returned

from alterego publisher

Bruce
{ Earth DC
Wayne
“publisher” :
“DC”
} Peter
Earth Marvel
Parker

Krypton Clark Kent DC


Quiz: What Is Returned

from alterego publisher

{ Bruce
“publisher” : Earth DC
Wayne
“DC”,
“from” :
“Earth” Peter
Earth Marvel
} Parker

Krypton Clark Kent DC


Resources

Queries Cheat Sheet
http://www.10gen.com/sites/default/files/downloads/
mongodb_qrc_queries.pdf


Demo: Query


Update

Update operations modify existing data in the DB

Mongo supports two update commands:
update() and save()

Update is the more general (and complex)


Update

The general form for update is:

db.collection.update(
<query>, <update>, <options> )

Which Entries What to do with
to update them


Update

The second argument to update() is an operator object

It tells update what to do with the data

Some keys you can use: “$set”, “$inc” “$push”,
“$pushAll”, “$addToSet”, “$pop”, “$pull”, “$pullAll”


Update: set

$set modifies a value or add a new value

Example:

db.posts.update(
{ title: “Why Is Your Cat Unhappy” },
{ $set : { “archived” : true } }
);


Quiz: $set

What happens here ?

db.cats.update(
{ color: “white” },
{ “$set” : { “owners” : [“John”, “Jim”] } }
);


Quiz: $set

Update owners array of the first cat with white color

If you want to update all objects, use multi

db.cats.update(
{ color: “white” },
{ “$set” : { “owners” : [“John”, “Jim”] } }
{ multi : true }
);


Deleting Data

remove() deletes objects from a collection

Takes a query and possibly a <justOne> arguments

Examples:

db.posts.remove({ “author” : “Father Angelo” })

db.music.remove({ “genres” : “pop” })

db.posts.remove({ “tags” : “funny” }, 1 );


The Driver

Hello C++ Mongo

C++ Objects

Coding Time


Hello Mongo

#include <iostream>
#include "client/dbclient.h"

using namespace mongo;

int main() {
try {
DBClientConnection c;
c.connect("localhost");

cout << "connected ok" << endl;
} catch( DBException &e ) {
cout << "caught " << e.what() << endl;
}
return 0;
}


Insert Data

BSONObjBuilder b;
b.append("name", "John");
b.append("age", 19);

BSONObj p1 = b.obj();
c.insert("test.people", p1);


Query Data

void printIfAge(DBClientConnection&c, int age) {
auto_ptr<DBClientCursor> cursor =
c.query("tutorial.persons", QUERY( "age" << age ) );

while( cursor->more() ) {
BSONObj p = cursor->next();
cout << p.getStringField("name") << endl;
}
}


Update Data

db.update( "tutorial.persons" ,
BSON( "name" << "Joe" << "age" << 33 ),
BSON( "$inc" << BSON( "visits" << 1 ) ) );


Delete Data

db.remove("tutorial.persons",
QUERY("age" << 19));


C++ Objects

DBClientConnection
represents a
connection
DBClientConnection c;
Methods: c.connect("localhost");

connect, auth

insert, query,
update, remove


C++ Objects

Query
data object
represents a
query QUERY( "age" << 33 <<
"school" << "UCLA" ).
sort("name");
Methods:
QUERY( "age" << GT << 30 << LT << 50 )
sort

Create with
macro QUERY


C++ Objects

DBClientCursor
Returned from
query()
auto_ptr<DBClientCursor> cursor =
Methods: c.query("tutorial.persons",
BSONObj());
more() while( cursor->more() )
cout << cursor->next().toString();
next()

Create with
auto_ptr


Coding Time

Mongo Score Board:
https://github.com/
ynonp/mongo-score

MoChat:
https://github.com/
ynonp/mochat


Thanks For Listening

Ynon Perek

Slides at:
ynonperek.com

Talk to me at:
ynon@ynonperek.com


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