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Django aggregates GROUP_CONCAT support for MySQL
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""" | |
From http://harkablog.com/inside-the-django-orm-aggregates.html | |
with a couple of fixes. | |
Usage: MyModel.objects.all().annotate(new_attribute=Concat('related__attribute', separator=':') | |
""" | |
from django.db.models import Aggregate | |
from django.db.models.sql.aggregates import Aggregate as SQLAggregate | |
class Concat(Aggregate): | |
def add_to_query(self, query, alias, col, source, is_summary): | |
aggregate = SQLConcat(col, source=source, is_summary=is_summary, **self.extra) | |
query.aggregates[alias] = aggregate | |
class SQLConcat(SQLAggregate): | |
sql_function = 'group_concat' | |
@property | |
def sql_template(self): | |
separator = self.extra.get('separator') | |
if separator: | |
return '%(function)s(%(field)s, "%(separator)s")' | |
else: | |
return '%(function)s(%(field)s)' |
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