NAME¶
MongoDBx::Class - Flexible ORM for MongoDB databases
VERSION¶
version 1.030002
SYNOPSIS¶
Normal usage:
use MongoDBx::Class;
# create a new instance of the module and load a model schema
my $dbx = MongoDBx::Class->new(namespace => 'MyApp::Model::DB');
# if MongoDBx::Class can't find your model schema (possibly because
# it exists in some different location), you can do this:
my $dbx = MongoDBx::Class->new(namespace => 'MyApp::Model::DB', search_dirs => ['/path/to/model/dir']);
# connect to a MongoDB server
my $conn = $dbx->connect(host => 'localhost', port => 27017);
# be safe by default
$conn->safe(1); # we could've also just passed "safe => 1" to $dbx->connect() above
# get a MongoDB database
my $db = $conn->get_database('myapp');
# insert a person
my $person = $db->get_collection('people')->insert({ name => 'Some Guy', birth_date => '1984-06-12', _class => 'Person' });
print "Created person ".$person->name." (".$person->id.")\n";
$person->update({ name => 'Some Smart Guy' });
$person->delete;
See MongoDBx::Class::ConnectionPool for simple connection pool usage.
DESCRIPTION¶
MongoDBx::Class is a flexible object relational mapper (ORM) for MongoDB
databases. Given a schema-like collection of document classes, MongoDBx::Class
expands MongoDB objects (hash-refs in Perl) from the database into objects of
those document classes, and collapses such objects back to the database.
MongoDBx::Class takes advantage of the fact that Perl's MongoDB driver is
Moose-based to extend and tweak the driver's behavior, instead of wrapping it.
This means MongoDBx::Class does not define its own syntax, so you simply use
it exactly as you would the MongoDB driver directly. That said,
MongoDBx::Class adds some sugar that enhances and simplifies the syntax
unobtrusively (either use it or don't). Thus, it is relatively easy to convert
your current MongoDB applications to MongoDBx::Class. A collection in
MongoDBx::Class "isa('MongoDB::Collection')", a database in
MongoDBx::Class "isa('MongoDB::Database')", etc.
As opposed to other ORMs (even non-MongoDB ones), MongoDBx::Class attempts to
stay as close as possible to MongoDB's non-schematic nature. While most ORMs
enforce using a single collection (or table in the SQL world) for every object
class, MongoDBx::Class allows you to store documents of different classes in
different collections (and even databases). A collection can hold documents of
many different classes. Not only that, as MongoDBx::Class is Moose based, you
can easily create very flexible schemas by using concepts such as inheritance
and roles. For example, say you have a collection called 'people' with
documents representing, well, people, but these people can either be teachers
or students. Also, students may assume the role "hall monitor". With
MongoDBx::Class, you can create a common base class, say "People",
and two more classes that extend it - "Teacher" and
"Student" with attributes that are only relevant to each one. You
also create a role called "HallMonitor", possibly with some methods
of its own. You can save all these "people documents" into a single
MongoDB collection, and when fetching documents from that collection, they
will be properly expanded to their correct classes (though you will have to
apply roles yourself - at least for now).
COMPARISON WITH OTHER MongoDB ORMs¶
As MongoDB is rather young, there aren't many options out there, though CPAN has
some pretty good ones, and will probably have more as MongoDB popularity
rises.
The first MongoDB ORM in CPAN was Mongoose, and while it's a very good ORM,
MongoDBx::Class was mainly written to overcome some limitations of Mongoose.
The biggest of these limitations is that in order to provide a more
comfortable syntax than MongoDB's native syntax, Mongoose makes the
unfortunate decision of being implemented as a singleton, meaning only one
instance of a Mongoose-based schema can be used in an application. That
essentially kills multithreaded applications. Say you have a Plack-based
(doesn't have to be Plack-based though) web application deployed via Starman
(or any other web server for that matter), which is a pre-forking web server -
you're pretty much doomed. As MongoDB's driver states, it doesn't support
connection pooling, so every fork has to have its own connection to the
MongoDB server. Mongoose being a singleton means your threads will not have a
connection to the server, and you're screwed. MongoDBx::Class does not suffer
this limitation. You can start as many connections as you like. If you're
running in a pre-forking environment, you don't have to worry about it at all.
Other differences from Mongoose include:
- •
- Mongoose creates its own syntax, MongoDBx::Class doesn't, you use
MongoDB's syntax directly.
- •
- A document class in Mongoose is connected to a single collection only, and
a collection can only have documents of that class. MongoDBx::Class
doesn't have that limitation. Do what you like.
- •
- Mongoose has limited support for multiple database usage. With
MongoDBx::Class, you can use as many databases as you want.
- •
- MongoDBx::Class is way faster. While I haven't performed any real
benchmarks, an application converted from Mongoose to MongoDBx::Class
showed an increase of speed in orders of magnitude.
- •
- In Mongoose, your document class attributes are expected to be read-write
(i.e. "is => 'rw'" in Moose), otherwise expansion will fail.
This is not the case with MongoDBx::Class, your attributes can safely be
read-only.
Another ORM for MongoDB is Mongrel, which doesn't use Moose and is thus lighter
(though as MongoDB is already Moose-based, I see no benefit here). It uses
Oogly for data validation (while Moose has its own type validation), and seems
to define its own syntax as well. Unfortunately, documentation is currently
lacking, and I haven't given it a try, so I can't draw specific comparisons
here.
Even before Mongoose was born, you could use MongoDB as a backend for KiokuDB,
by using KiokuDB::Backend::MongoDB. However, KiokuDB is considered a database
of its own and uses some conventions which doesn't fit well with MongoDB.
Mongoose::Intro already gives a pretty convincing case when and why you should
or shouldn't want to use KiokuDB.
CONNECTION POOLING¶
Since version 0.9, "MongoDBx::Class" provides experimental, simple
connection pooling for applications. Take a look at
MongoDBx::Class::ConnectionPool for more information.
CAVEATS AND THINGS TO CONSIDER¶
There are a few caveats and important facts to take note of when using
MongoDBx::Class as of today:
- •
- MongoDBx::Class's flexibility is dependent on its ability to recognize
which class a document in a MongoDB collection expands to. Currently,
MongoDBx::Class requires every document to have an attribute called
"_class" that contains the name of the document class to use.
This isn't very comfortable, but works. I'm still thinking of ways to
expand documents without this. This pretty much means that you will have
to perform some preparations to use existing MongoDB database with
MongoDBx::Class - you will have to update every document in the database
with the "_class" attribute.
- •
- References (representing joins) are expected to be in the DBRef format, as
defined in
<http://www.mongodb.org/display/DOCS/Database+References>. If your
database references aren't in this format, you'll have to convert them
first.
- •
- The '_id' attribute of all your documents has to be an internally
generated MongoDB::OID. This limitation may or may not be lifted in the
future.
TUTORIAL¶
To start using MongoDBx::Class, please read MongoDBx::Class::Tutorial. It also
contains a list of frequently asked questions.
ATTRIBUTES¶
namespace¶
A string representing the namespace of the MongoDB schema used (e.g.
"MyApp::Schema"). Your document classes, structurally speaking,
should be descendants of this namespace (e.g.
"MyApp::Schema::Article", "MyApp::Schema::Post").
search_dirs¶
An array-ref of directories in which to search for the document classes. Not
required, useful if for some reason MongoDBx::Class can't find your document
classes.
doc_classes¶
A hash-ref of document classes found when loading the schema.
CLASS METHODS¶
new( namespace => $namespace )¶
Creates a new instance of this module. Requires the namespace of the database
schema to use. The schema will be immediately loaded, but no connection to a
MongoDB server is made yet.
OBJECT METHODS¶
connect( %options )¶
Initiates a new connection to a MongoDB server running on a certain host and
listening to a certain port. %options is the hash of attributes that can be
passed to "new()" in MongoDB::Connection, plus the 'safe' attribute
from MongoDBx::Class::Connection. You're mostly expected to provide the 'host'
and 'port' options. If a host is not provided, 'localhost' is used. If a port
is not provided, 27017 (MongoDB's default port) is used. Returns a
MongoDBx::Class::Connection object.
NOTE: Since version 0.7, the created connection object isn't saved in the top
MongoDBx::Class object, but only returned, in order to be more like how
connection is made in MongoDB (and to allow multiple connections). This change
breaks backwords compatibility.
pool( [ type => $type, max_conns => $max_conns, params => \%params, ... ] )¶
Creates a new connection pool (see MongoDBx::Class::ConnectionPool for more
info) and returns it. "type" is either 'rotated' or 'backup' (the
default). "params" is a hash-ref of parameters that can be passed to
"MongoDB::Connection->new()" when creating connections in the
pool. See "ATTRIBUTES" in MongoDBx::Class::ConnectionPool for a
complete list of attributes that can be passed.
INTERNAL METHODS¶
The following methods are only to be used internally.
BUILD()¶
Automatically called when creating a new instance of this module. This loads the
schema and saves a hash-ref of document classes found in the object. Automatic
loading courtesy of Module::Pluggable.
AUTHOR¶
Ido Perlmuter, "<ido at ido50.net>"
BUGS¶
Please report any bugs or feature requests to "bug-mongodbx-class at
rt.cpan.org", or through the web interface at
<
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MongoDBx-Class>. I will
be notified, and then you'll automatically be notified of progress on your bug
as I make changes.
SUPPORT¶
You can find documentation for this module with the perldoc command.
perldoc MongoDBx::Class
You can also look for information at:
- •
- RT: CPAN's request tracker
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=MongoDBx::Class>
- •
- AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/MongoDBx::Class>
- •
- CPAN Ratings
<http://cpanratings.perl.org/d/MongoDBx::Class>
- •
- Search CPAN
<http://search.cpan.org/dist/MongoDBx::Class/>
SEE ALSO¶
MongoDB, Mongoose, Mongrel, KiokuDB::Backend::MongoDB.
ACKNOWLEDGEMENTS¶
- •
- Rodrigo de Oliveira, author of Mongoose, whose code greatly assisted me in
writing MongoDBx::Class.
- •
- Thomas Mueller, for adding support for the Transient trait.
- •
- Dan Dascalescu, for fixing typos and other problems in the
documentation.
LICENSE AND COPYRIGHT¶
Copyright 2010-2014 Ido Perlmuter.
This program is free software; you can redistribute it and/or modify it under
the terms of either: the GNU General Public License as published by the Free
Software Foundation; or the Artistic License.
See
http://dev.perl.org/licenses/ for more information.