Non-Relational Databases

Non-Relational Databases
San Francisco Perl Mongers
Kristina Chodorow
September 3, 2009

Who am I?
Software Engineer at 10gen
Perl, PHP, Java drivers

Scaling

Technique #1:
literally scale

Technique #1:
literally scale
(Courtesy of Ask Bjorn Hansen)
$3,200
$4,000,000
x 1250 =

Technique #2: shard
now-yesterday
yesterday-
the day before
the day before-
the day before that

Technique #3: master-slave replication
R
W
W
R/W?
W
R

Cassandra
Designed by Facebook
Distributed - eventually consistent
Column-oriented

Cassandra
Writes ALWAYS work
Two types of reads:
high performance
guaranteed correct
R/W atomic within column family

Cassandra
Row-oriented:
joe, 34, karen, 25, bob, 50
Column-oriented:
joe, karen, bob, 34, 25, 50

Project Voldemort
Key/value store
Automatic replication/partitioning
75 Github forks
“It is basically a just a big, distributed, persistent, fault-tolerant hash table.”

Tokyo Cabinet
Another key/value store
Blazing fast… theoretically
Lua for server-side scripting

Tokyo Cabinet
Key/value pairs
Array store
Index-able Hash
{
name : “Chris”
age : 27,
DOB : “January 1”
}

CouchDB
Master-Master Replication
Map/Reduce
REST API

CouchDB Futon

MongoDB

MongoDB
Ease of use
Scalable
Dynamic queries - similar “feel” to SQL
Speed of key/value stores (almost)
Power of RDBMSs (almost)

The Perl Driver
Available at Github:
www.github.com/mongodb/mongo-perl-driver/
Install the Perl driver
$ perl Makefile.PL && sudo make install
Available on CPAN (but old):
http://search.cpan.org/~flora/MongoDB-0.01/

Downloading MongoDB
www.mongodb.org
Binaries available for Linux, Mac, Windows, Solaris

Start the DB Server
$ mkdir ~/db
$
$ tar zxvfmongodb-<OS>-1.0.0.tgz
$ cdmongodb-<OS>-1.0.0
$ bin/mongod --dbpath ~/db

Connecting to the Database
use MongoDB;
my $connection = MongoDB::Connection->new;
my $db = $connection->get_database(‘test’);
my $collection = $db->get_collection(‘foo’);

Inserting
my $id = $collection->insert(
{
title => ‘My first blog post’,
author => ‘Joe’,
content => ‘Hello, world!’
comments => []
}
);

MongoDB::OID
an autogenerated primary key
my $id = $collection->insert({whatever});
print Dumper($id);
--------------------------------------------
$VAR1 = bless( { 'value' => '4a9700dba5f9107c5cbc9a9c' }, 'MongoDB::OID' )

Updating
$collection->update({_id => $id},
{‘$push’ => {comments =>
{
‘author’ => ‘Fred’,
‘comment’ => ‘Dumb post.”
}
}});

…which gives us:
print Dumper($collection->find_one());
--------------------------------------------
{
title : ‘My first blog post’,
author : ‘Joe’,
content : ‘Hello, world!’
comments : [{
‘author’ : ‘Fred’,
‘comment’ : ‘Dumb post’
}]
}

Magic (not the Perl kind)
$gt, $gte, $lt, $lte, $eq, $neq, $exists,
$set, $mod, $where, $in, $nin, $inc
$push, $pull, $pop, $pushAll, $popAll
$c->query({ x => {‘$gt’ => 4}})

Querying
my $commented_by_fred =
$collection->query({
“comments.author” : “Fred”
});
my $commented_by_fred =
$collection->query({
“comments.author” : qr/fred/i
});

$where
$collection->find_one({‘$where’ :
‘this.y == (this.x + this.z)’});
Will work:
{x => 1, y => 4, z => 3}
{x => “hi”, y => “hibye”, z => “bye”}
Won’t work:
{x => 1, y => 1}

Optimizing $where
$collection->find_one({
‘name’ => ‘Sally’,
‘age’ => {‘$gt’ => 18},
‘$where’ => ‘Array.sort(this.interests)[2] == “volleyball”’});

Speaking of indexing…
$collection->ensure_index({“age” => “ascending”});
$collection->ensure_index({
“name” => “descending”,
“ts” => “descending”,
“comments.author” => “ascending”
});

Cursors
my $cursor = $coll->query({“foo” => “bar”});
my $obj;
while (my $obj = $cursor->next) {
...
}
my @all = $cursor->all;

Paging
my $cursor = $coll->query->
sort({ts => -1})->
skip($page_num * $results_per_page)->
limit($results_per_page);
my @page = $cursor->all;

Logging
insert/update/remove is fast
Capped collections
Schemaless
$inc for counts

Thank you!
kristina@10gen.com
@kchodorow
@mongodb
irc.freenode.net#mongodb
www.mongodb.org