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Fixed #30913 -- Added support for covering indexes on PostgreSQL 11+.

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Hannes Ljungberg 2019-10-31 13:33:53 +01:00 • committed by Mariusz Felisiak
parent f997b5e6ae
commit 8c7992f658
20 changed files with 719 additions and 41 deletions
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25
docs/ref/models/constraints.txt
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@ -73,7 +73,7 @@ constraint.
``UniqueConstraint``
====================
.. class:: UniqueConstraint(*, fields, name, condition=None, deferrable=None)
.. class:: UniqueConstraint(*, fields, name, condition=None, deferrable=None, include=None)
Creates a unique constraint in the database.
@ -145,3 +145,26 @@ enforced immediately after every command.
Deferred unique constraints may lead to a `performance penalty
<https://www.postgresql.org/docs/current/sql-createtable.html#id-1.9.3.85.9.4>`_.
``include``
-----------
.. attribute:: UniqueConstraint.include
.. versionadded:: 3.2
A list or tuple of the names of the fields to be included in the covering
unique index as non-key columns. This allows index-only scans to be used for
queries that select only included fields (:attr:`~UniqueConstraint.include`)
and filter only by unique fields (:attr:`~UniqueConstraint.fields`).
For example::
UniqueConstraint(name='unique_booking', fields=['room', 'date'], include=['full_name'])
will allow filtering on ``room`` and ``date``, also selecting ``full_name``,
while fetching data only from the index.
``include`` is supported only on PostgreSQL.
Non-key columns have the same database restrictions as :attr:`Index.include`.