Hello,
Is there a way to handle many-to-many relationship with raw sql queries ?
I have the following model:
from django.db import models
class Tag(models.Model):
name = models.CharField(max_length=512, unique=True)
class Bookmark(models.Model):
link = models.CharField(max_length=512)
title = models.CharField(max_length=512)
tags = models.ManyToManyField(Tag)
added_at = models.DateField()
Using Bookmark.objetcs.all() will result in a subquery for each row of the
bookmark table which is not acceptable for performance reasons.
First question is there a way to fetch all the content with a single query ?
Second question is it possible to use raw sql queries. I tried the
following:
bookmarks = Bookmark.objects.raw(
'SELECT * FROM bookmarkmanager_bookmark b '
'LEFT JOIN bookmarkmanager_bookmark_tags bt ON (b.id =
bt.bookmark_id) '
'LEFT JOIN bookmarkmanager_tag t ON (bt.tag_id = t.id)'
)
But when i tried to access the tags attribute on a bookmark i get the
following exception:
ValueError: "<Bookmark: Bookmark object>" needs to have a value for field
"bookmark" before this many-to-many relationship can be used.
Thanks in advance,
Matthieu
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