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Adds missing features to Django ORM for working with data in bulk operations

Project description

Django BulkModel

BulkModel adds additional features that makes it easier to interact with data in bulk.

Below is a brief summary of the project. Read the full documentation


BulkModels and features

Create a bulkmodel by inheriting from BulkModel:

from bulkmodel.models import BulkModel

class Foo(BulkModel):
    name = models.CharField(max_length=50, blank=False)
    value = models.IntegerField(null=False)

Here's some new functionality that's available to you now:

1) Get a queryset after a bulk create

Sometimes you need created data to be returned from the database with a primary key assigned to each model instance for full processing.

This is typically the case when you bulk create some data and then want to assign foreign keys to other models, thereby requiring the primary keys on the new data.

from random import randint, random, string

ls = []
for i in range(10):
    ls.append(Foo(
        # random string
        name = ''.join(random.choices(string.ascii_uppercase, 25)),

        # random value
        value = randint(0, 1000),
    ))

# create instances and return a queryset of the created items
foos = Foo.objects.bulk_create(ls, return_queryset=True)

2) Heterogeneous updates

Django's update() queryset method allows you to update homogeneous data.

That is, all the model instances in the queryset are updated to the same value (or applied the same change when using F expressions) for the specified columns.

BulkModels allow you to update data heterogeneously. That is, each model instance in a queryset can take on a different value in a single query execution.

To do this, use the update_fields() queryset method, like so:

for foo in foos:
    foo.value += randint(100, 200)

# update all fields that changed
foos.update_fields()

# or update just the value field
foos.update_fields('value')

This will only execute one query, regardless of how many fields are in the model are updated.

3) Concurrent writes

BulkModels support concurrent writes out of the box, which can significantly speed up write time given a large enough database server.

Concurrent writes are available on all the write queryset methods (bulk_create, update, update_fields, copy_from_objects).

foos = ...

# concurrently write foos into the database
Foo.objects.bulk_create(foos, concurrent=True, batch_size=1000, max_concurrent_workers=10)

# a regular (homogeneous) update can be written concurrently
foos.update(concurrent=True, batch_size=1000, max_concurrent_workers=10)

# and so can a heterogeneous update
foos.update_fields(concurrent=True, batch_size=1000, max_concurrent_workers=10)

4) Additional signals

Django ships with the following signals for interacting with data:

  • Saving a single instance: pre_save and post_save
  • Deleting data: pre_delete and post_delete
  • Changing a many to many relationship: m2m_changed

What's missing from this list are signals when data is created in bulk and updated in bulk.

BulkModels ship with additional signals when data is created:

  • pre_bulk_create / post_bulk_create are fired when data is being written from bulk_create
  • pre_copy_from_instances / post_copy_from_instances are fired when data is being written from a data buffer (via the copy_from_objects queryset method)

And these signals when data is updated:

  • pre_update / post_update are fired when a homogeneous update is applied
  • pre_update_fields / post_update_fields are fired when a heterogeneous update is applied

You can optionally turn off signal emission in any write function by setting send_signals=False (signals are emitted by default).

5) More

A few more features come with BulkModels, like offline connection management, copying data to and from the database via in-memory buffers, and queryset chunking.

See the full list of features


Installation

First make sure you have django >= 1.9 installed. It's always recommended to update to the latest version of Django.

For concurrency features to work you'll need Python 3.4+ and access to asyncio

Then install the package from pypi:

pip install django-bulkmodel

Add bulkmodel to your INSTALLED_APPS:

INSTALLED_APPS = [
    ...
    'bulkmodel',
]

Inherit your existing models from BulkModel, or create new models to inherit from this class:

from django.db import models
from bulkmodel.models import BulkModel

class MyModel(BulkModel):
    ...

Make migrations:

./manage.py makemigrations <name-of-your-app> # for new apps
./manage.py makemigrations # for existing apps with migrations

And apply them:

./manage.py migrate

You can also do a partial installation if you don't want to migrate all your models.

For more instructions read the full installation instructions documentation


Full documentation

Read the full documentation

License

This software is made available under the Apache v2 License; see the LICENSE file for details.

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