Create and manage Postgres SQL Views in Django
Project description
SQL Views for Postgres
Adds first-class support for PostgreSQL Views in the Django ORM. For of the original django-pgviews by mypebble with support for Django 2.2+.
Installation
Install via pip:
pip install django-pgviews-redux
Add to installed applications in settings.py:
INSTALLED_APPS = (
# ...
'django_pgviews',
)
Examples
from django.db import models
from django_pgviews import view as pg
class Customer(models.Model):
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
is_preferred = models.BooleanField(default=False)
class Meta:
app_label = 'myapp'
class PreferredCustomer(pg.View):
projection = ['myapp.Customer.*',]
dependencies = ['myapp.OtherView',]
sql = """SELECT * FROM myapp_customer WHERE is_preferred = TRUE;"""
class Meta:
app_label = 'myapp'
db_table = 'myapp_preferredcustomer'
managed = False
NOTE It is important that we include the managed = False
in the Meta
so
Django 1.7 migrations don't attempt to create DB tables for this view.
The SQL produced by this might look like:
CREATE VIEW myapp_preferredcustomer AS
SELECT * FROM myapp_customer WHERE is_preferred = TRUE;
To create all your views, run python manage.py sync_pgviews
You can also specify field names, which will map onto fields in your View:
from django_pgviews import view as pg
VIEW_SQL = """
SELECT name, post_code FROM myapp_customer WHERE is_preferred = TRUE
"""
class PreferredCustomer(pg.View):
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
sql = VIEW_SQL
Usage
To map onto a View, simply extend pg_views.view.View
, assign SQL to the
sql
argument and define a db_table
. You must always set managed = False
on the Meta
class.
Views can be created in a number of ways:
- Define fields to map onto the VIEW output
- Define a projection that describes the VIEW fields
Define Fields
Define the fields as you would with any Django Model:
from django_pgviews import view as pg
VIEW_SQL = """
SELECT name, post_code FROM myapp_customer WHERE is_preferred = TRUE
"""
class PreferredCustomer(pg.View):
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
sql = VIEW_SQL
class Meta:
managed = False
db_table = 'my_sql_view'
Define Projection
django-pgviews
can take a projection to figure out what fields it needs to
map onto for a view. To use this, set the projection
attribute:
from django_pgviews import view as pg
class PreferredCustomer(pg.View):
projection = ['myapp.Customer.*',]
sql = """SELECT * FROM myapp_customer WHERE is_preferred = TRUE;"""
class Meta:
db_table = 'my_sql_view'
managed = False
This will take all fields on myapp.Customer
and apply them to
PreferredCustomer
Features
Updating Views
Sometimes your models change and you need your Database Views to reflect the new data. Updating the View logic is as simple as modifying the underlying SQL and running:
python manage.py sync_pgviews --force
This will forcibly update any views that conflict with your new SQL.
Dependencies
You can specify other views you depend on. This ensures the other views are
installed beforehand. Using dependencies also ensures that your views get
refreshed correctly when using sync_pgviews --force
.
Note: Views are synced after the Django application has migrated and adding models to the dependency list will cause syncing to fail.
Example:
from django_pgviews import view as pg
class PreferredCustomer(pg.View):
dependencies = ['myapp.OtherView',]
sql = """SELECT * FROM myapp_customer WHERE is_preferred = TRUE;"""
class Meta:
app_label = 'myapp'
db_table = 'myapp_preferredcustomer'
managed = False
Materialized Views
Postgres 9.3 and up supports materialized views which allow you to cache the results of views, potentially allowing them to load faster.
However, you do need to manually refresh the view. To do this automatically, you can attach signals and call the refresh function.
Example:
from django_pgviews import view as pg
VIEW_SQL = """
SELECT name, post_code FROM myapp_customer WHERE is_preferred = TRUE
"""
class Customer(models.Model):
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
is_preferred = models.BooleanField(default=True)
class PreferredCustomer(pg.MaterializedView):
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
sql = VIEW_SQL
@receiver(post_save, sender=Customer)
def customer_saved(sender, action=None, instance=None, **kwargs):
PreferredCustomer.refresh()
Postgres 9.4 and up allow materialized views to be refreshed concurrently, without blocking reads, as long as a
unique index exists on the materialized view. To enable concurrent refresh, specify the name of a column that can be
used as a unique index on the materialized view. Unique index can be defined on more than one column of a materialized
view. Once enabled, passing concurrently=True
to the model's refresh method will result in postgres performing the
refresh concurrently. (Note that the refresh method itself blocks until the refresh is complete; concurrent refresh is
most useful when materialized views are updated in another process or thread.)
Example:
from django_pgviews import view as pg
VIEW_SQL = """
SELECT id, name, post_code FROM myapp_customer WHERE is_preferred = TRUE
"""
class PreferredCustomer(pg.MaterializedView):
concurrent_index = 'id, post_code'
sql = VIEW_SQL
name = models.CharField(max_length=100)
post_code = models.CharField(max_length=20)
@receiver(post_save, sender=Customer)
def customer_saved(sender, action=None, instance=None, **kwargs):
PreferredCustomer.refresh(concurrently=True)
Custom Schema
You can define any table name you wish for your views. They can even live inside your own custom PostgreSQL schema.
from django_pgviews import view as pg
class PreferredCustomer(pg.View):
sql = """SELECT * FROM myapp_customer WHERE is_preferred = TRUE;"""
class Meta:
db_table = 'my_custom_schema.preferredcustomer'
managed = False
Sync Listeners
django-pgviews 0.5.0 adds the ability to listen to when a post_sync
event has
occurred.
view_synced
Fired every time a VIEW is synchronised with the database.
Provides args:
sender
- View Classupdate
- Whether the view to be updatedforce
- Whetherforce
was passedstatus
- The result of creating the view e.g.EXISTS
,FORCE_REQUIRED
has_changed
- Whether the view had to change
all_views_synced
Sent after all Postgres VIEWs are synchronised.
Provides args:
sender
- AlwaysNone
Django Compatibility
Django Version | Django-PGView Version |
---|---|
1.4 and down | Unsupported |
1.5 | 0.0.1 |
1.6 | 0.0.3 |
1.7 | 0.0.4 |
1.9 | 0.1.0 |
1.10 | 0.2.0 |
2.2 | 0.6.0 |
3.0 | 0.6.0 |
Django 1.7 Note
Django 1.7 changed how models are loaded so that it's no longer possible to do
sql = str(User.objects.all().query)
because the dependent models aren't
yet loaded by Django.
Django 1.9 Note
You now have to use the .view
module directly.
Django 1.10 Note
When updating to Django 1.10, if you see AttributeError: can't set attribute
when you try to migrate or run tests, you need to check your migrations for
where _base_manager
or _default_manager
get set on the model and replace it
with objects
inside the migration.
This also applies to Django MPTT who have covered this in a bit more detail.
Python 3 Support
Django PGViews Redux only supports Python 3.6+.
Project details
Release history Release notifications | RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
Source Distribution
Built Distribution
Hashes for django-pgviews-redux-0.6.0.tar.gz
Algorithm | Hash digest | |
---|---|---|
SHA256 | 1e870c8274b3eca3492d0eb39e00924426d6896ec44612de0a2e9f36fe455b9a |
|
MD5 | 1f3c20a8f3e6bb51d7a784fae65bd5b4 |
|
BLAKE2b-256 | ebc6693ac962b69ee1cdcc3325bae0ec0b6860ae489d35710a38d5d179843f3f |
Hashes for django_pgviews_redux-0.6.0-py3-none-any.whl
Algorithm | Hash digest | |
---|---|---|
SHA256 | 0008a50e4df49d5eea2e5428f23fa11bc425c47fb4c844ce017c0189e3578b99 |
|
MD5 | c79b21dfaa8a117cc30f622e79f9a4f3 |
|
BLAKE2b-256 | 33c4e725cba5c55565df1d272d2992d97be497f08f7a9de6d810aa75d02f2cbb |