Query Inspector is a Django application providing middleware for inspecting and reporting SQL queries executed for each web request.
Works with Django (1.4, 1.5, 1.6, 1.7) and Python (2.6, 2.7, 3.3, 3.4).
Example log output:
[SQL] 17 queries (4 duplicates), 34 ms SQL time, 243 ms total request time
The statistics can also be added to response headers, for easier debugging without looking into the server logs:
X-QueryInspect-Num-SQL-Queries: 17
X-QueryInspect-Duplicate-SQL-Queries: 4
X-QueryInspect-Total-SQL-Time: 34 ms
X-QueryInspect-Total-Request-Time: 243 ms
The duplicate queries can also be shown in the log:
[SQL] repeated query (6x): SELECT "customer_role"."id",
"customer_role"."contact_id", "customer_role"."name"
FROM "customer_role" WHERE "customer_role"."contact_id" = ?
The duplicate queries are detected by ignoring any integer values in the SQL statement. The reasoning is that most of the duplicate queries in Django are due to results not being cached or pre-fetched properly, so Django needs to look up related fields afterwards. This lookup is done by the object ID, which is in most cases an integer.
The heuristic is not 100% precise so it may have some false positives or negatives, but is a very good starting point for most Django projects.
For each duplicate query, the Python traceback can also be shown, which may help with identifying why the query has been executed:
File "/vagrant/api/views.py", line 178, in get
return self.serialize(self.object_qs)
File "/vagrant/customer/views.py", line 131, in serialize
return serialize(objs, include=includes)
File "/vagrant/customer/serializers.py", line 258, in serialize_contact
lambda obj: [r.name for r in obj.roles.all()]),
File "/vagrant/customer/serializers.py", line 258, in <lambda>
lambda obj: [r.name for r in obj.roles.all()]),
Install from the Python Package Index:
pip install django-queryinspect
Add the middleware to your Django settings:
MIDDLEWARE_CLASSES += (
'qinspect.middleware.QueryInspectMiddleware',
)
Enable Django's DEBUG setting (the SQL query logging doesn't work without
it):
DEBUG = True
And set one or more Query Inspector settings flags depending on the desired behaviour:
# Whether the Query Inspector should do anything (default: False)
QUERY_INSPECT_ENABLED = True
# Whether to log the stats via Django logging (default: True)
QUERY_INSPECT_LOG_STATS = True
# Whether to add stats headers (default: True)
QUERY_INSPECT_HEADER_STATS = True
# Whether to log duplicate queries (default: False)
QUERY_INSPECT_LOG_QUERIES = True
# Whether to include tracebacks in the logs (default: False)
QUERY_INSPECT_LOG_TRACEBACKS = True
# Project root (one or several colon-separated directories, default empty)
QUERY_INSPECT_TRACEBACK_ROOTS = '/path/to/my/django/project/'
Complete tracebacks of an entire request are usually huge, but only a few
entries in the traceback are of the interest (usually only the few that
represent the code you're working on). To include only these entries of interest
in the shown tracebacks, you can set QUERY_INSPECT_TRACEBACK_ROOTS to the
root directory of your project.
Since Django apps need not be under the same directory, the setting also accepts colon-separated list of directories - traceback entry referencing any file under any of these directories will be included.
Copyright (C) 2014. Good Code
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