eloquent 0.5

The Eloquent ORM provides a simple yet beautiful ActiveRecord implementation.

The Eloquent ORM provides a simple yet beautiful ActiveRecord implementation.

It is inspired by the database part of the Laravel framework, but largely modified to be more pythonic.

The full documentation is available here: http://eloquent.readthedocs.org

Installation

You can install Eloquent in 2 different ways:

• The easier and more straightforward is to use pip

pip install eloquent

• Install from source using the official repository (https://github.com/sdispater/eloquent)

The different dbapi packages are not part of the package dependencies, so you must install them in order to connect to corresponding databases:

• Postgres: pyscopg2

• MySQL: PyMySQL or mysqlclient

• Sqlite: The sqlite3 module is bundled with Python by default

Basic Usage

Configuration

All you need to get you started is the configuration describing your database connections and passing it to a DatabaseManager instance.

from eloquent import DatabaseManager, Model

config = {
    'mysql': {
        'driver': 'mysql',
        'host': 'localhost',
        'database': 'database',
        'username': 'root',
        'password': '',
        'prefix': ''
    }
}

db = DatabaseManager(config)
Model.set_connection_resolver(db)

Defining a model

class User(Model):
    pass

Note that we did not tell the ORM which table to use for the User model. The plural “snake case” name of the class name will be used as the table name unless another name is explicitly specified. In this case, the ORM will assume the User model stores records in the users table. You can specify a custom table by defining a __table__ property on your model:

class User(Model):

    __table__ = 'my_users'

The ORM will also assume that each table has a primary key column named id. You can define a __primary_key__ property to override this convention. Likewise, you can define a __connection__ property to override the name of the database connection that should be used when using the model.

Once a model is defined, you are ready to start retrieving and creating records in your table. Note that you will need to place updated_at and created_at columns on your table by default. If you do not wish to have these columns automatically maintained, set the __timestamps__ property on your model to False.

Retrieving all models

users = User.all()

Retrieving a record by primary key

user = User.find(1)

print(user.name)

Querying using models

users = User.where('votes', '>', 100).take(10).get()

for user in users:
    print(user.name)

Aggregates

You can also use the query builder aggregate functions:

count = User.where('votes', '>', 100).count()

If you feel limited by the builder’s fluent interface, you can use the where_raw method:

users = User.where_raw('age > ? and votes = 100', [25]).get()

Chunking Results

If you need to process a lot of records, you can use the chunk method to avoid consuming a lot of RAM:

for users in User.chunk(100):
    for user in users:
        # ...

Specifying the query connection

You can specify which database connection to use when querying a model by using the on method:

user = User.on('connection-name').find(1)

If you are using read / write connections, you can force the query to use the “write” connection with the following method:

user = User.on_write_connection().find(1)

Mass assignment

When creating a new model, you pass attributes to the model constructor. These attributes are then assigned to the model via mass-assignment. Though convenient, this can be a serious security concern when passing user input into a model, since the user is then free to modify any and all of the model’s attributes. For this reason, all models protect against mass-assignment by default.

To get started, set the __fillable__ or __guarded__ properties on your model.

Defining fillable attributes on a model

The __fillable__ property specifies which attributes can be mass-assigned.

class User(Model):

    __fillable__ = ['first_name', 'last_name', 'email']

Defining guarded attributes on a model

The __guarded__ is the inverse and acts as “blacklist”.

class User(Model):

    __guarded__ = ['id', 'password']

You can also block all attributes from mass-assignment:

__guarded__ = ['*']

Insert, update and delete

Saving a new model

To create a new record in the database, simply create a new model instance and call the save method.

user = User()

user.name = 'John'

user.save()

You can also use the create method to save a model in a single line, but you will need to specify either the __fillable__ or __guarded__ property on the model since all models are protected against mass-assigment by default.

After saving or creating a new model with auto-incrementing IDs, you can retrieve the ID by accessing the object’s id attribute:

inserted_id = user.id

Using the create method

# Create a new user in the database
user = User.create(name='John')

# Retrieve the user by attributes, or create it if it does not exist
user = User.first_or_create(name='John')

# Retrieve the user by attributes, or instantiate it if it does not exist
user = User.first_or_new(name='John')

Updating a retrieved model

user = User.find(1)

user.name = 'Foo'

user.save()

You can also run updates as queries against a set of models:

affected_rows = User.where('votes', '>', 100).update(status=2)

Deleting an existing model

To delete a model, simply call the delete model:

user = User.find(1)

user.delete()

Deleting an existing model by key

User.destroy(1)

User.destroy(1, 2, 3)

You can also run a delete query on a set of models:

affected_rows = User.where('votes', '>' 100).delete()

Updating only the model’s timestamps

If you want to only update the timestamps on a model, you can use the touch method:

user.touch()

Timestamps

By default, the ORM will maintain the created_at and updated_at columns on your database table automatically. Simply add these timestamp columns to your table. If you do not wish for the ORM to maintain these columns, just add the __timestamps__ property:

class User(Model):

    __timestamps__ = False

Providing a custom timestamp format

If you whish to customize the format of your timestamps (the default is the ISO Format) that will be returned when using the to_dict or the to_json methods, you can override the get_date_format method:

class User(Model):

    def get_date_format():
        return 'DD-MM-YY'

Converting to dictionaries / JSON

Converting a model to a dictionary

When building JSON APIs, you may often need to convert your models and relationships to dictionaries or JSON. So, Eloquent includes methods for doing so. To convert a model and its loaded relationship to a dictionary, you may use the to_dict method:

user = User.with_('roles').first()

return user.to_dict()

Note that entire collections of models can also be converted to dictionaries:

return User.all().to_dict()

Converting a model to JSON

To convert a model to JSON, you can use the to_json method!

return User.find(1).to_json()

Query Builder

Introduction

The database query builder provides a fluent interface to create and run database queries. It can be used to perform most database operations in your application, and works on all supported database systems.

Selects

Retrieving all row from a table

users = db.table('users').get()

for user in users:
    print(user['name'])

Chunking results from a table

for users in db.table('users').chunk(100):
    for user in users:
        # ...

Retrieving a single row from a table

user = db.table('users').where('name', 'John').first()
print(user['name'])

Retrieving a single column from a row

user = db.table('users').where('name', 'John').pluck('name')

Retrieving a list of column values

roles = db.table('roles').lists('title')

This method will return a list of role titles. It can return a dictionary if you pass an extra key parameter.

roles = db.table('roles').lists('title', 'name')

Specifying a select clause

users = db.table('users').select('name', 'email').get()

users = db.table('users').distinct().get()

users = db.table('users').select('name as user_name').get()

Adding a select clause to an existing query

query = db.table('users').select('name')

users = query.add_select('age').get()

Using where operators

users = db.table('users').where('age', '>', 25).get()

Or statements

users = db.table('users').where('age', '>', 25).or_where('name', 'John').get()

Using Where Between

users = db.table('users').where_between('age', [25, 35]).get()

Using Where Not Between

users = db.table('users').where_not_between('age', [25, 35]).get()

Using Where In

users = db.table('users').where_in('id', [1, 2, 3]).get()

users = db.table('users').where_not_in('id', [1, 2, 3]).get()

Using Where Null to find records with null values

users = db.table('users').where_null('updated_at').get()

Order by, group by and having

query = db.table('users').order_by('name', 'desc')
query = query.group_by('count')
query = query.having('count', '>', 100)

users = query.get()

Offset and limit

users = db.table('users').skip(10).take(5).get()

users = db.table('users').offset(10).limit(5).get()

Joins

The query builder can also be used to write join statements.

Basic join statement

db.table('users') \
    .join('contacts', 'users.id', '=', 'contacts.user_id') \
    .join('orders', 'users.id', '=', 'orders.user_id') \
    .select('users.id', 'contacts.phone', 'orders.price') \
    .get()

Left join statement

db.table('users').left_join('posts', 'users.id', '=', 'posts.user_id').get()

You can also specify more advance join clauses:

clause = JoinClause('contacts').on('users.id', '=', 'contacts.user_id').or_on(...)

db.table('users').join(clause).get()

If you would like to use a “where” style clause on your joins, you may use the where and or_where methods on a join. Instead of comparing two columns, these methods will compare the column against a value:

clause = JoinClause('contacts').on('users.id', '=', 'contacts.user_id').where('contacts.user_id', '>', 5)

db.table('users').join(clause).get()

Advanced where

Sometimes you may need to create more advanced where clauses such as “where exists” or nested parameter groupings. It is pretty easy to do with the Eloquent query builder

Parameter grouping

db.table('users') \
    .where('name', '=', 'John') \
    .or_where(
        db.query().where('votes', '>', 100).where('title', '!=', 'admin')
    ).get()

The query above will produce the following SQL:

SELECT * FROM users WHERE name = 'John' OR (votes > 100 AND title != 'Admin')

Exists statement

db.table('users').where_exists(
    db.table('orders').select(db.raw(1)).where_raw('order.user_id = users.id')
)

The query above will produce the following SQL:

SELECT * FROM users
WHERE EXISTS (
    SELECT 1 FROM orders WHERE orders.user_id = users.id
)

Aggregates

The query builder also provides a variety of aggregate methods, ` such as count, max, min, avg, and sum.

users = db.table('users').count()

price = db.table('orders').max('price')

price = db.table('orders').min('price')

price = db.table('orders').avg('price')

total = db.table('users').sum('votes')

Raw expressions

Sometimes you may need to use a raw expression in a query. These expressions will be injected into the query as strings, so be careful not to create any SQL injection points! To create a raw expression, you may use the raw() method:

db.table('users') \
    .select(db.raw('count(*) as user_count, status')) \
    .where('status', '!=', 1) \
    .group_by('status') \
    .get()

Inserts

Insert records into a table

db.table('users').insert(email='[e-mail]', votes=0)

db.table('users').insert({
    'email': '[e-mail]',
    'votes': 0
})

It is important to note that there is two notations available. The reason is quite simple: the dictionary notation, though a little less practical, is here to handle columns names which cannot be passed as keywords arguments.

Inserting records into a table with an auto-incrementing ID

If the table has an auto-incrementing id, use insert_get_id to insert a record and retrieve the id:

id = db.table('users').insert_get_id({
    'email': '[e-mail]',
    'votes': 0
})

Inserting multiple record into a table

db.table('users').insert([
    {'email': '[e-mail]', 'votes': 0},
    {'email': '[e-mail]', 'votes': 0}
])

Updates

Updating records

db.table('users').where('id', 1).update(votes=1)

db.table('users').where('id', 1).update({'votes': 1})

Like the insert statement, there is two notations available. The reason is quite simple: the dictionary notation, though a little less practical, is here to handle columns names which cannot be passed as keywords arguments.

Incrementing or decrementing the value of a column

db.table('users').increment('votes')  # Increment the value by 1

db.table('users').increment('votes', 5)  # Increment the value by 5

db.table('users').decrement('votes')  # Decrement the value by 1

db.table('users').decrement('votes', 5)  # Decrement the value by 5

You can also specify additional columns to update:

db.table('users').increment('votes', 1, name='John')

Deletes

Deleting records

db.table('users').where('age', '<', 25).delete()

Delete all records

db.table('users').delete()

Truncate

db.table('users').truncate()

Unions

The query builder provides a quick and easy way to “union” two queries:

first = db.table('users').where_null('first_name')

users = db.table('users').where_null('last_name').union(first).get()

The union_all method is also available.

Read / Write connections

Sometimes you may wish to use one database connection for SELECT statements, and another for INSERT, UPDATE, and DELETE statements. Eloquent makes this easy, and the proper connections will always be used whether you use raw queries, the query builder or the actual ORM

Here is an example of how read / write connections should be configured:

config = {
    'mysql': {
        'read': [
            'host': '192.168.1.1'
        ],
        'read': [
            'host': '192.168.1.2'
        ],
        'driver': 'mysql',
        'database': 'database',
        'username': 'root',
        'password': '',
        'prefix': ''
    }
}

Note that two keys have been added to the configuration dictionary: read and write. Both of these keys have dictionary values containing a single key: host. The rest of the database options for the read and write connections will be merged from the main mysql dictionary. So, you only need to place items in the read and write dictionaries if you wish to override the values in the main dictionary. So, in this case, 192.168.1.1 will be used as the “read” connection, while 192.168.1.2 will be used as the “write” connection. The database credentials, prefix, character set, and all other options in the main mysql dictionary will be shared across both connections.

Database transactions

To run a set of operations within a database transaction, you can use the transaction method which is a context manager:

with db.transaction():
    db.table('users').update({votes: 1})
    db.table('posts').delete()

Note

Any exception thrown within a transaction block will cause the transaction to be rolled back automatically.

Sometimes you may need to start a transaction yourself:

db.begin_transaction()

You can rollback a transaction with the rollback method:

db.rollback()

You can also commit a transaction via the commit method:

db.commit()

By default, all underlying DBAPI connections are set to be in autocommit mode meaning that you don’t need to explicitly commit after each operation.

Accessing connections

When using multiple connections, you can access them via the connection() method:

users = db.connection('foo').table('users').get()

You also can access the raw, underlying dbapi connection instance:

db.connection().get_connection()

Sometimes, you may need to reconnect to a given database:

db.reconnect('foo')

If you need to disconnect from the given database, use the disconnect method:

db.disconnect('foo')