sdispater / Orator
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Orator
.. image:: https://travis-ci.org/sdispater/orator.png :alt: Orator Build status :target: https://travis-ci.org/sdispater/orator
The Orator ORM provides a simple yet beautiful ActiveRecord implementation.
It is inspired by the database part of the Laravel framework <http://laravel.com>_,
but largely modified to be more pythonic.
The full documentation is available here: http://orator-orm.com/docs
Installation
You can install Orator in 2 different ways:
- The easier and more straightforward is to use pip
.. code-block:: bash
pip install orator
- Install from source using the official repository (https://github.com/sdispater/orator)
The different dbapi packages are not part of the package dependencies, so you must install them in order to connect to corresponding databases:
- Postgres:
psycopg2 - MySQL:
PyMySQLormysqlclient - Sqlite: The
sqlite3module 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.
.. code-block:: python
from orator import DatabaseManager, Model
config = {
'mysql': {
'driver': 'mysql',
'host': 'localhost',
'database': 'database',
'user': 'root',
'password': '',
'prefix': ''
}
}
db = DatabaseManager(config)
Model.set_connection_resolver(db)
Defining a model
.. code-block:: python
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:
.. code-block:: python
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
.. code-block:: python
users = User.all()
Retrieving a record by primary key
.. code-block:: python
user = User.find(1)
print(user.name)
Querying using models
.. code-block:: python
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:
.. code-block:: python
count = User.where('votes', '>', 100).count()
If you feel limited by the builder's fluent interface, you can use the where_raw method:
.. code-block:: python
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:
.. code-block:: python
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:
.. code-block:: python
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:
.. code-block:: python
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.
.. code-block:: python
class User(Model):
__fillable__ = ['first_name', 'last_name', 'email']
Defining guarded attributes on a model
The __guarded__ is the inverse and acts as "blacklist".
.. code-block:: python
class User(Model):
__guarded__ = ['id', 'password']
You can also block all attributes from mass-assignment:
.. code-block:: python
__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.
.. code-block:: python
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-assignment 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:
.. code-block:: python
inserted_id = user.id
Using the create method
.. code-block:: python
# 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
.. code-block:: python
user = User.find(1)
user.name = 'Foo'
user.save()
You can also run updates as queries against a set of models:
.. code-block:: python
affected_rows = User.where('votes', '>', 100).update(status=2)
.. TODO: push method
Deleting an existing model
To delete a model, simply call the delete model:
.. code-block:: python
user = User.find(1)
user.delete()
Deleting an existing model by key
.. code-block:: python
User.destroy(1)
User.destroy(1, 2, 3)
You can also run a delete query on a set of models:
.. code-block:: python
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:
.. code-block:: python
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:
.. code-block:: python
class User(Model):
__timestamps__ = False
Providing a custom timestamp format
If you wish 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:
.. code-block:: python
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, Orator includes methods for doing so. To convert a model and its loaded relationship to a dictionary,
you may use the to_dict method:
.. code-block:: python
user = User.with_('roles').first()
return user.to_dict()
Note that entire collections of models can also be converted to dictionaries:
.. code-block:: python
return User.all().serailize()
Converting a model to JSON
To convert a model to JSON, you can use the to_json method!
.. code-block:: python
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
.. code-block:: python
users = db.table('users').get()
for user in users:
print(user['name'])
Chunking results from a table
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
for users in db.table('users').chunk(100):
for user in users:
# ...
Retrieving a single row from a table
.. code-block:: python
user = db.table('users').where('name', 'John').first()
print(user['name'])
Retrieving a single column from a row
.. code-block:: python
user = db.table('users').where('name', 'John').pluck('name')
Retrieving a list of column values
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
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.
.. code-block:: python
roles = db.table('roles').lists('title', 'name')
Specifying a select clause
~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
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
.. code-block:: python
query = db.table('users').select('name')
users = query.add_select('age').get()
Using where operators
.. code-block:: python
users = db.table('users').where('age', '>', 25).get()
Or statements
~~~~~~~~~~~~~
.. code-block:: python
users = db.table('users').where('age', '>', 25).or_where('name', 'John').get()
Using Where Between
~~~~~~~~~~~~~~~~~~~
.. code-block:: python
users = db.table('users').where_between('age', [25, 35]).get()
Using Where Not Between
.. code-block:: python
users = db.table('users').where_not_between('age', [25, 35]).get()
Using Where In
.. code-block:: python
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
.. code-block:: python
users = db.table('users').where_null('updated_at').get()
Order by, group by and having
.. code-block:: python
query = db.table('users').order_by('name', 'desc')
query = query.group_by('count')
query = query.having('count', '>', 100)
users = query.get()
Offset and limit
~~~~~~~~~~~~~~~~
.. code-block:: python
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
~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
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
~~~~~~~~~~~~~~~~~~~
.. code-block:: python
db.table('users').left_join('posts', 'users.id', '=', 'posts.user_id').get()
You can also specify more advance join clauses:
.. code-block:: python
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:
.. code-block:: python
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 Orator query builder
Parameter grouping
~~~~~~~~~~~~~~~~~~
.. code-block:: python
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:
.. code-block:: sql
SELECT * FROM users WHERE name = 'John' OR (votes > 100 AND title != 'Admin')
Exists statement
~~~~~~~~~~~~~~~~
.. code-block:: python
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:
.. code-block:: 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``.
.. code-block:: python
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:
.. code-block:: python
db.table('users') \
.select(db.raw('count(*) as user_count, status')) \
.where('status', '!=', 1) \
.group_by('status') \
.get()
Inserts
-------
Insert records into a table
~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
db.table('users').insert(email='[email protected]', votes=0)
db.table('users').insert({
'email': '[email protected]',
'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:
.. code-block:: python
id = db.table('users').insert_get_id({
'email': '[email protected]',
'votes': 0
})
Inserting multiple record into a table
.. code-block:: python
db.table('users').insert([
{'email': '[email protected]', 'votes': 0},
{'email': '[email protected]', 'votes': 0}
])
Updates
-------
Updating records
~~~~~~~~~~~~~~~~
.. code-block:: python
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
.. code-block:: python
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:
.. code-block:: python
db.table('users').increment('votes', 1, name='John')
Deletes
Deleting records
.. code-block:: python
db.table('users').where('age', '<', 25).delete()
Delete all records
.. code-block:: python
db.table('users').delete()
Truncate
.. code-block:: python
db.table('users').truncate()
Unions
------
The query builder provides a quick and easy way to "union" two queries:
.. code-block:: python
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:
Read / Write connections
========================
Sometimes you may wish to use one database connection for SELECT statements,
and another for INSERT, UPDATE, and DELETE statements. Orator 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:
.. code-block:: python
config = {
'mysql': {
'read': {
'host': '192.168.1.1'
},
'write': {
'host': '192.168.1.2'
},
'driver': 'mysql',
'database': 'database',
'user': '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:
.. code-block:: python
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:
.. code-block:: python
db.begin_transaction()
You can rollback a transaction with the ``rollback`` method:
.. code-block:: python
db.rollback()
You can also commit a transaction via the ``commit`` method:
.. code-block:: python
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:
.. code-block:: python
users = db.connection('foo').table('users').get()
You also can access the raw, underlying dbapi connection instance:
.. code-block:: python
db.connection().get_connection()
Sometimes, you may need to reconnect to a given database:
.. code-block:: python
db.reconnect('foo')
If you need to disconnect from the given database, use the ``disconnect`` method:
.. code-block:: python
db.disconnect('foo')