Any-of constraint building using SQLAlchemy

anyof_constraint.py

import operator as op

import sqlalchemy as sa

__all__ = "anyof_constraint",


def anyof_constraint(*cols, at_least_one: bool = False) -> sa.CheckConstraint:
    if len(cols) < 2:
        raise ValueError("At least 2 columns MUST be provided to create any-of constraint!")
    # NOTE(zeronineseven): Inspired by https://hashrocket.com/blog/posts/modeling-polymorphic-associations-in-a-relational-database#exclusive-belongs-to-aka-exclusive-arc-
    return sa.CheckConstraint(
        (op.eq if at_least_one else op.le)(
            functools.reduce(lambda acc, c: acc + c, (sa.cast(c.is_not(None), sa.Integer) for c in cols)), 1
        )
    )