#32226: QuerySet.explain(format='json') outputs repr'd JSON on PostgreSQL
-------------------------------------+-------------------------------------
Reporter: Adam | Owner: nobody
(Chainz) Johnson |
Type: Bug | Status: new
Component: Database | Version: 3.0
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Call `.explain(format='json')` on a `QuerySet` on PostgreSQL, and the
result *looks* like JSON, but isn't:
{{{
In [5]: User.objects.filter(is_staff=True).explain(format='json')
Out[5]: "[{'Plan': {'Node Type': 'Seq Scan', 'Parallel Aware': False,
'Relation Name': 'auth_user', 'Alias': 'auth_user', 'Startup Cost': 0.0,
'Total Cost': 478.12, 'Plan Rows': 23, 'Plan Width': 157, 'Filter':
'is_staff'}}]"
}}}
One needs to use `ast.literal_eval` and `json.dumps` to get real JSON text
that can be pasted into tools like [https://tatiyants.com/pev/ PostgreSQL
explain viewer]:
{{{
In [10]: explain =
User.objects.filter(is_staff=True).explain(format='json') ;
print(json.dumps(ast.literal_eval(explain)))
[{"Plan": {"Node Type": "Seq Scan", "Parallel Aware": false, "Relation
Name": "auth_user", "Alias": "auth_user", "Startup Cost": 0.0, "Total
Cost": 478.12, "Plan Rows": 23, "Plan Width": 157, "Filter": "is_staff"}}]
}}}
I guess this is because `psycopg2` loads the JSON as a Python list of
dicts, then `SQLCompiler.explain_query` does `yield ' '.join(str(c) for c
in row)`, which turns that list into its `repr()`.
--
Ticket URL: <https://code.djangoproject.com/ticket/32226>
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