Method test_reduce_aliased_union_2

test/sql/test_selectable.py:2802–2887

(self)

        )

    def test_reduce_aliased_union_2(self):
        metadata = MetaData()
        page_table = Table(
            "page", metadata, Column("id", Integer, primary_key=True)
        )
        magazine_page_table = Table(
            "magazine_page",
            metadata,
            Column(
                "page_id", Integer, ForeignKey("page.id"), primary_key=True
            ),
        )
        classified_page_table = Table(
            "classified_page",
            metadata,
            Column(
                "magazine_page_id",
                Integer,
                ForeignKey("magazine_page.page_id"),
                primary_key=True,
            ),
        )

        # this is essentially the union formed by the ORM's
        # polymorphic_union function. we define two versions with
        # different ordering of selects.
        #
        # the first selectable has the "real" column
        # classified_page.magazine_page_id

        pjoin = union(
            select(
                page_table.c.id,
                magazine_page_table.c.page_id,
                classified_page_table.c.magazine_page_id,
            ).select_from(
                page_table.join(magazine_page_table).join(
                    classified_page_table
                )
            ),
            select(
                page_table.c.id,
                magazine_page_table.c.page_id,
                cast(null(), Integer).label("magazine_page_id"),
            ).select_from(page_table.join(magazine_page_table)),
        ).alias("pjoin")
        eq_(
            util.column_set(
                sql_util.reduce_columns(
                    [pjoin.c.id, pjoin.c.page_id, pjoin.c.magazine_page_id]
                )
            ),
            util.column_set([pjoin.c.id]),
        )

        # the first selectable has a CAST, which is a placeholder for
        # classified_page.magazine_page_id in the second selectable.
        # reduce_columns needs to take into account all foreign keys