Metadata-Version: 1.1
Name: django-prefetch-plus
Version: 0.3.3
Summary: More generic form of django prefetch_related
Home-page: https://github.com/jdroloson/django-prefetch-plus
Author: Jordan Rolson
Author-email: jdroloson@gmail.com
License: BSD License
Description-Content-Type: UNKNOWN
Description: =====
        Prefetch Plus
        =====
        
        Prefetch Plus aims to add additional flexibility to django's built in
        prefetch_related functionality. 
        
        Using the built in prefetch_related you can only select objects related through
        reverse ForeignKey relationships. With PrefetchPlus you can slect objects related
        through any mapping of columns from one table to another.
        
        This allows forsomething much more similar to the capabilities of a
        databases left outer join.
        
        Installation
        -----------
        pip install django-prefetch-plus
        
        Usage
        -----------
        
        As Manager:
        
        Prefetch Plus comes with the PrefetchPlusQuerySet which provides a similar
        interface to prefetch_related:
        ```
        from prefetch_plus import PrefetchPlusQuerySet
        from django.db import models
        
        GENRES = (
            ...
            ('romance', 'Romance'),
            ('mystery', 'Mystery'),
        )
        
        
        class Author(models.Model)
            ...
            genre = models.CharField(
                choices = GENRES
            )
            ...
            objects = PrefetchPlusQuerySet.as_manager()
            
        class Book(models.Model)
            ...
            author = models.ForeignKey(
                Author
            )
        
            genre = models.CharField(
                choices = GENRES
            )
            ...
        
        # We want to have author's of books review other books in the same genre.
        
        # The old way
        for author in Author.objects.all():
            # Typical N+1 db query that cannot be resolved with builtin prefetch_related
            author.books_to_review = list(Book.objects.filter(genre=author.genre))
            
        # The new way
        # This will grab all of the Books that share a genre with any author,
        # then it will attach attach the list of books in each genre to the matching
        # author(s)
        authors = Author.objects.prefetch_plus(
            to_attr='books_to_review',
            query_set=Book.objects.all(),
            obj_cols='genre',
            qset_cols='genre'
        ).all()
        # obj_cols & qset_cols can also be tuples of columns to allow for
        # "composite keys". The tuple must be the same length and the matches are
        # getattr(object, obj_cols[i]) == getattr(qset_object, qset_cols[i]) for any i
         
        # Prefetch plus works across related objects. I highly recommend you remember to
        # select_related if you do this. Otherwise, you aren't getting any benefit out
        # of this
        authors = Author.objects.prefetch_plus(
            to_attr='books_to_review',
            query_set=Book.objects.select_related('author').all(),
            obj_cols='genre',
            qset_cols='author__genre'
        ).all()
        ```
        
        Without the manager:
        
        You don't have to use the manager if you don't want, it simply calls the
        following helper function at the appropriate time
        
        ```
        from prefetch_plus import do_prefetch_plus
        from django.db import models
        
        GENRES = (
            ...
            ('romance', 'Romance'),
            ('mystery', 'Mystery'),
        )
        
        
        class Author(models.Model)
            ...
            genre = models.CharField(
                choices = GENRES
            )
            ...
        
        class Book(models.Model)
            ...
            author = models.ForeignKey(
                Author
            )
        
            genre = models.CharField(
                choices = GENRES
            )
            ...
        
        # We want to have author's of books review other books in the same genre.
        
        authors = Author.objects.all()
        
        do_prefetch_plus(
            objects=authors,
            to_attr='books_to_review',
            query_set=Book.objects.all(),
            obj_cols='genre',
            qset_cols='genre'
        )
        ```
        
        Version History
        -----------
        0.3.3: Made Prefetch plus faster at the cost of potentially grabbing extra
             records in the case of composite keys. Fixed support for 2.7
Platform: UNKNOWN
Classifier: Environment :: Web Environment
Classifier: Framework :: Django
Classifier: Framework :: Django :: 1.8
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Topic :: Internet :: WWW/HTTP
Classifier: Topic :: Internet :: WWW/HTTP :: Dynamic Content
