id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36981	Add PostgreSQL num_nonnulls (code provided)	Robin Christ	Shubh Rai	"I recently implemented ""anyOf"" / ""tagged union"" fields. I added specialized CheckConstraints using num_nonnulls

The code looks like this:

{{{
class NumNonNulls(Func):
    """"""
    Wraps PostgreSQL `num_nonnulls`.

    Returns the number of non-null arguments as an integer.  Can be used with
    `F()` references to model fields (including e.g. OneToOne) relationships.

    Example::

        NumNonNulls(F(""one_to_one_rel_1""), F(""one_to_one_rel_1""))
        ->  SQL: num_nonnulls(""one_to_one_rel_1_id"", ""one_to_one_rel_2_id"")
    """"""

    function = ""num_nonnulls""

    def __init__(self, *expressions: object, **extra) -> None:
        super().__init__(*expressions, output_field=IntegerField(), **extra)


class NumNonNullsEq(Func):
    """"""
    Renders ``num_nonnulls(<args>) = <n>`` as a boolean expression.

    Suitable for use as the `condition` of a `CheckConstraint`.

    Parameters
    ----------
    *expressions:
        The expressions (e.g. `F()` expressions) to pass to `num_nonnulls`.
    count:
        The value or expression the result must equal.

    Example::

        NumNonNullsEq(F(""one_to_one_rel_1""), F(""one_to_one_rel_2""), count=1)
        -> SQL: num_nonnulls(""one_to_one_rel_1_id"", ""one_to_one_rel_2_id"") = 1
    """"""

    arg_joiner = "" = ""
    template = ""%(expressions)s""

    def __init__(self, *expressions: object, count: object, **extra) -> None:
        if not expressions:
            raise ValueError(""NumNonNullsEq() requires at least one expression."")

        super().__init__(
            NumNonNulls(*expressions),
            count,
            output_field=BooleanField(),
        )
}}}

Is there any interest from Django's side in this?"	New feature	closed	Database layer (models, ORM)	6.0	Normal	needsnewfeatureprocess		Shubh Rai	Unreviewed	1	0	0	0	0	0