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Django implementantion for Query By Example (QBE)
Django Query by Example (QBE)
:synopsis: Admin tool in order to get custom reports.
The objective of django-qbe is provide a assited and interactive way of making complex queries with no technical knowledge (or minimal) to get custom reports from the objects of Django models.
Based on QBE_ proposal from IBM®, django-qbe is intended to remove the limitations of Django QuerySets objects and to use the whole expresive power of the subjacent SQL.
Installation
Using the Python Package Index (PyPI_) and easy_install script::
$ easy_install django_qbe
Or through pip::
$ pip install django_qbe
But you also can download the django_qbe
directory using git::
$ git clone git://github.com/versae/qbe.git $ cp -r qbe/django_qbe /path/to/your/project
Adding to the project settings::
INSTALLED_APPS = ( # [...] django builtins applications 'django_qbe', # [...] Any other application )
Add the context processor django.core.context_processors.static
::
TEMPLATES = [
{
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
# [...] django context processors
'django.template.context_processors.static',
# [...] Any other context processors
],
},
},
]
See the Django documentation on static files
__ for details.
__ staticfiles_
And adding the urlconf in your project urls.py::
# qbe
url(r'^qbe/', include('django_qbe.urls')),
That's all. Then you can access to http://host:port/qbe However, you can add a link from your admin page changing the admin index template fo your AdminSite::
class AdminSite(admin.AdminSite): index_template = "qbe_index.html"
Or adding in your custom admin index template the next javascript::
Saved queries ^^^^^^^^^^^^^
If you optionally want to store queries in your database, feel free to
install the also included app django_qbe.savedqueries
::
INSTALLED_APPS = ( # [...] django builtins applications 'django_qbe', 'django_qbe.savedqueries', # [...] Any other application )
Then run the syncdb
or optionally South_'s migrate
management command
to create the savedqueries_saved_query
table.
After that there will be a new option to save a query in a model instance and
an admin interface to browse the saved queries, or direclty from the command
line using the command qbe_export
::
$ python manage.py help qbe_export $ python manage.py qbe_export <query_hash> $ python manage.py qbe_export <query_hash> --output test.csv $ python manage.py qbe_export <query_hash> --output test.xls --format xls $ python manage.py qbe_export <query_hash> --output test.xls --format xls --db-alias default
.. _South: http://south.readthedocs.org/
Settings
The next lines show de available settings and its default values.
Admin module name to add admin urls in results::
QBE_ADMIN = "admin"
Set your own admin site if it's different to usual django.contrib.admin.site::
QBE_ADMIN_SITE ="admin.admin_site"
Function to control to users with access to QBE::
QBE_ACCESS_FOR = lambda user: user.is_staff
Some options for the query builder form::
QBE_ALIASES = False # It allows to add an alias to a model field QBE_GROUP_BY = False # It allows to group by in a query QBE_SHOW_ROW_NUMBER = True # It disables number rows in results
Path to QBE formats export file, in order to add custom export formats::
QBE_FORMATS_EXPORT = "qbe_formats"
Path to custom QBE operators for the criteria::
QBE_CUSTOM_OPERATORS = "qbe_operators"
Custom Operators
Use Custom Operators only if you know what you are doing and at your own risks!
If you need to define custom operators, in a file qbe_operators.py
in your
project root, you need to create a new class that extends
django_qbe.operators.CustomOperator
::
import datetime from django.utils import timezone from django_qbe.operators import CustomOperator
class SinceDaysAgo(CustomOperator): slug = 'since-days-ago' # REQUIRED and must be unique label = 'Since Days Ago' # REQUIRED
def get_params(self):
if len(self.params):
return self.params
now = timezone.now()
today = now.replace(hour=0, minute=0, second=0, microsecond=0)
tomorrow = today + datetime.timedelta(days=1)
date_since = today - datetime.timedelta(days=int(self.value))
operator = "gt"
lookup_since = self._get_lookup(operator, str(date_since))
lookup_until = self._get_lookup(operator, str(tomorrow))
self.params.append(lookup_since)
self.params.append(lookup_until)
return self.params
def get_wheres(self):
if len(self.wheres):
return self.wheres
lookup_cast = self._db_operations.lookup_cast
for operator in ["gte", "lt"]:
db_operator = self._db_operators[operator]
self.wheres.append(u"%s %s" % (
lookup_cast(operator) % self.db_field,
db_operator)
)
return self.wheres
Your custom operator must have 2 attributes, slug
and label
in order
to be displayed in the Criteria dropdown.
The get_params
and get_wheres
methods must return an iterable instance
(eg. list), otherwise it gets converted to a list.
If you dont want to write it in your models.py
make sure that it is
imported in one of the files that are evaluated at runtime (eg. models.py
or urls.py
) in order to register your Custom Operator.
.. _QBE: http://www.google.com/url?sa=t&source=web&ct=res&cd=2&ved=0CB4QFjAB&url=http%3A%2F%2Fpages.cs.wisc.edu%2F~dbbook%2FopenAccess%2FthirdEdition%2Fqbe.pdf&ei=_UD5S5WSBYP5-Qb-18i8CA&usg=AFQjCNHMv-Pua285zhWT8DevuZFj2gfYKA&sig2=-sTEDWjJhnTaixh2iJfsAw .. _PyPI: http://pypi.python.org/pypi/django_qbe/ .. _staticfiles: http://docs.djangoproject.com/en/dev/howto/static-files/