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@@ -11,8 +11,9 @@ Profile first
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=============
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=============
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As general programming practice, this goes without saying. Find out :ref:`what
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As general programming practice, this goes without saying. Find out :ref:`what
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-queries you are doing and what they are costing you
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-<faq-see-raw-sql-queries>`. You may also want to use an external project like
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+queries you are doing and what they are costing you <faq-see-raw-sql-queries>`.
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+Use :meth:`.QuerySet.explain` to understand how specific ``QuerySet``\s are
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+executed by your database. You may also want to use an external project like
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django-debug-toolbar_, or a tool that monitors your database directly.
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django-debug-toolbar_, or a tool that monitors your database directly.
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Remember that you may be optimizing for speed or memory or both, depending on
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Remember that you may be optimizing for speed or memory or both, depending on
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@@ -114,6 +115,14 @@ When you have a lot of objects, the caching behavior of the ``QuerySet`` can
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cause a large amount of memory to be used. In this case,
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cause a large amount of memory to be used. In this case,
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:meth:`~django.db.models.query.QuerySet.iterator()` may help.
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:meth:`~django.db.models.query.QuerySet.iterator()` may help.
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+Use ``explain()``
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+-----------------
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+
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+:meth:`.QuerySet.explain` gives you detailed information about how the database
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+executes a query, including indexes and joins that are used. These details may
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+help you find queries that could be rewritten more efficiently, or identify
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+indexes that could be added to improve performance.
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+
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Do database work in the database rather than in Python
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Do database work in the database rather than in Python
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======================================================
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======================================================
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Tom Forbes