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Refs #16614 -- Made QuerySet.iterator() use server-side cursors on PostgreSQL.

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Thanks to Josh Smeaton for the idea of implementing server-side cursors
in PostgreSQL from the iterator method, and Anssi Kääriäinen and Kevin
Turner for their previous work. Also Simon Charette and Tim Graham for
review.
This commit is contained in:
François Freitag
2016-06-03 15:31:21 -07:00
committed by Tim Graham
parent 53bffe8d03
commit f3b7c05936
13 changed files with 165 additions and 31 deletions
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18
docs/ref/databases.txt
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@@ -171,6 +171,24 @@ If you need to add a PostgreSQL extension (like ``hstore``, ``postgis``, etc.)
using a migration, use the
:class:`~django.contrib.postgres.operations.CreateExtension` operation.
.. _postgresql-server-side-cursors:
Server-side cursors
-------------------
.. versionadded:: 1.11
When using :meth:`QuerySet.iterator()
<django.db.models.query.QuerySet.iterator>`, Django opens a :ref:`server-side
cursor <psycopg2:server-side-cursors>`. By default, PostgreSQL assumes that
only the first 10% of the results of cursor queries will be fetched. The query
planner spends less time planning the query and starts returning results
faster, but this could diminish performance if more than 10% of the results are
retrieved. PostgreSQL's assumptions on the number of rows retrieved for a
cursor query is controlled with the `cursor_tuple_fraction`_ option.
.. _cursor_tuple_fraction: https://www.postgresql.org/docs/current/static/runtime-config-query.html#GUC-CURSOR-TUPLE-FRACTION
Test database templates
-----------------------