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A small package for Django to ease the creation of temporary tables, based on model definitions and querysets

Project description

Author: Keryn Knight
Version: 0.1.4

A small package for Django to ease the creation of database temporary tables.

It doesn’t need to be in your INSTALLED_APPS

Usage

Define a mostly normal Django model, like so:

from django.db import models

class MyCoolModel(models.Model):
    value = models.PositiveIntegerField(primary_key=True)

    class Meta:
        abstract = True
        managed = False

Pay special attention to the Meta attributes. It’ll complain otherwise.

Provide a definition for the temporary table somewhere:

from storedqueries import TemporaryTable

class MyTemporaryTable(TemporaryTable):
    model = MyCoolModel
    queryset = Somedata.objects.order_by('?').annotate(value=models.F('key_name')).values_list('value').iterator()

Make use of the temporary table:

from django.http import JsonResponse

def myview(request, *args, **kwargs):
    with MyTemporaryTable() as TemporaryModel:
        keys = TemporaryModel.objects.all()
        data = tuple(Somedata.objects.filter(key_name__in=keys))
        return JsonResponse({'values': data})

Using the with my_cls() as thing: syntax will create a uniquely named temporary table using the queryset connection and data to fill it, when the with scope closes, the temporary table is dropped. The TemporaryModel variable will be a subclass of MyCoolModel bound to the unique name for the temporary table.

If you have a query which cannot be defined at module scope, you can do:

class MyTemporaryTable(TemporaryTable):
    model = MyCoolModel
    def source_queryset(self):
        return Somedata.objects.filter(created__lte=timezone.now()).annotate(value=models.F('key_name')).values_list('value').iterator()

If you still cannot get the query correct, because it has a dependency on something like request.user etc, you can do:

def myview(request, *args, **kwargs):
    qs = Somedata.objects.filter(user=request.user.pk)
    with MyTemporaryTable(queryset=qs) as TemporaryModel:
        raise NotImplementedError("Dynamic queryset binding")

or probably even:

def myview(request, *args, **kwargs):
    qs = Somedata.objects.filter(user=request.user.pk)
    with TemporaryTable(model=MyCoolModel, queryset=qs) as TemporaryModel:
        raise NotImplementedError("Dynamic model AND queryset binding")

The license

It’s FreeBSD. There’s should be a LICENSE file in the root of the repository, and in any archives.


Copyright (c) 2019, Keryn Knight All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


Change history for django-storedqueries

0.1.4

  • Changed the open and close methods of TemporaryTableEditor to avoid using the cursor as a context manager for greater compatibility (ie: I have an old internal project where this could be useful)

0.1.3

  • Raise an exception at runtime if the temporary model being passed in delares ForeignKey etc without setting related_name="+" for each.
  • Add functionality for MySQL to detect if it can use the MEMORY engine.

0.1.2

  • Initial release

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