#36707: Prefetch related query throwing "Expression tree is too large" error
after
updating to Django 5.2 when using sqlite3 DB
-------------------------------------+-------------------------------------
Reporter: Alexandru Chirila | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 5.2 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
After updating to version 5.2.7 from 4.2.15 of Django some queries with
prefetch related that used to work with the sqlite3 engine no longer work
and are throwing the "Expression tree is too large" error.
-----
Example working with 4.2:
{{{
In [1]: import django
In [2]: django.__version__
Out[2]: '4.2.15'
In [3]: from dv.models import Organisation
In [4]: x =
list(Organisation.objects.all().prefetch_related("roles__project"))
In [5]: len(x)
Out[5]: 22321
}}}
----
Example working in 5.2 **without** prefetch
{{{
In [1]: import django
In [2]: django.__version__
Out[2]: '5.2.7'
In [3]: from dv.models import Organisation
In [4]: x = list(Organisation.objects.all())
In [5]: len(x)
Out[5]: 22321
}}}
---
Example of it not working with prefetch:
{{{
In [1]: import django
In [2]: django.__version__
Out[2]: '5.2.7'
In [3]: from dv.models import Organisation
In [4]: x =
list(Organisation.objects.all().prefetch_related("roles__project"))
---------------------------------------------------------------------------
OperationalError Traceback (most recent call
last)
File ~/PycharmProjects/dataviz/.venv/lib/python3.12/site-
packages/django/db/backends/utils.py:105, in CursorWrapper._execute(self,
sql, params, *ignored_wrapper_args)
104 else:
--> 105 return self.cursor.execute(sql, params)
File ~/PycharmProjects/dataviz/.venv/lib/python3.12/site-
packages/django/db/backends/sqlite3/base.py:360, in
SQLiteCursorWrapper.execute(self, query, params)
359 query = self.convert_query(query, param_names=param_names)
--> 360 return super().execute(query, params)
OperationalError: Expression tree is too large (maximum depth 1000)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/36707>
Django <https://code.djangoproject.com/>
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