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Fixed #34604 -- Corrected fallback SQL for n-ary logical XOR.

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An n-ary logical XOR Q(…) ^ Q(…) ^ … ^ Q(…) should evaluate to true
when an odd number of its operands evaluate to true, not when exactly
one operand evaluates to true.
This commit is contained in:
Anders Kaseorg 2023-05-29 21:59:22 -07:00 • committed by Mariusz Felisiak
parent ee36e101e8
commit b81e974e9e
4 changed files with 44 additions and 4 deletions
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15
docs/ref/models/querysets.txt
View file

@ -2021,7 +2021,8 @@ may be generated.
XOR (``^``)
~~~~~~~~~~~
Combines two ``QuerySet``\s using the SQL ``XOR`` operator.
Combines two ``QuerySet``\s using the SQL ``XOR`` operator. A ``XOR``
expression matches rows that are matched by an odd number of operands.
The following are equivalent::
@ -2044,13 +2045,21 @@ SQL equivalent:
.. code-block:: sql
(x OR y OR ... OR z) AND
1=(
1=MOD(
(CASE WHEN x THEN 1 ELSE 0 END) +
(CASE WHEN y THEN 1 ELSE 0 END) +
...
(CASE WHEN z THEN 1 ELSE 0 END) +
(CASE WHEN z THEN 1 ELSE 0 END),
2
)
.. versionchanged:: 5.0
In older versions, on databases without native support for the SQL
``XOR`` operator, ``XOR`` returned rows that were matched by exactly
one operand. The previous behavior was not consistent with MySQL,
MariaDB, and Python behavior.
Methods that do not return ``QuerySet``\s
-----------------------------------------