Method _joincond_scan_left_right

lib/sqlalchemy/sql/selectable.py:1490–1556

(
        cls,
        a: FromClause,
        a_subset: Optional[FromClause],
        b: FromClause,
        consider_as_foreign_keys: Optional[AbstractSet[ColumnClause[Any]]],
    )

    @classmethod
    @util.preload_module("sqlalchemy.sql.util")
    def _joincond_scan_left_right(
        cls,
        a: FromClause,
        a_subset: Optional[FromClause],
        b: FromClause,
        consider_as_foreign_keys: Optional[AbstractSet[ColumnClause[Any]]],
    ) -> collections.defaultdict[
        Optional[ForeignKeyConstraint],
        List[Tuple[ColumnClause[Any], ColumnClause[Any]]],
    ]:
        sql_util = util.preloaded.sql_util

        a = coercions.expect(roles.FromClauseRole, a)
        b = coercions.expect(roles.FromClauseRole, b)

        constraints: collections.defaultdict[
            Optional[ForeignKeyConstraint],
            List[Tuple[ColumnClause[Any], ColumnClause[Any]]],
        ] = collections.defaultdict(list)

        for left in (a_subset, a):
            if left is None:
                continue
            for fk in sorted(
                b.foreign_keys,
                key=lambda fk: fk.parent._creation_order,
            ):
                if (
                    consider_as_foreign_keys is not None
                    and fk.parent not in consider_as_foreign_keys
                ):
                    continue
                try:
                    col = fk.get_referent(left)
                except exc.NoReferenceError as nrte:
                    table_names = {t.name for t in sql_util.find_tables(left)}
                    if nrte.table_name in table_names:
                        raise
                    else:
                        continue

                if col is not None:
                    constraints[fk.constraint].append((col, fk.parent))
            if left is not b:
                for fk in sorted(
                    left.foreign_keys,
                    key=lambda fk: fk.parent._creation_order,
                ):
                    if (
                        consider_as_foreign_keys is not None
                        and fk.parent not in consider_as_foreign_keys
                    ):
                        continue
                    try:
                        col = fk.get_referent(b)
                    except exc.NoReferenceError as nrte:
                        table_names = {t.name for t in sql_util.find_tables(b)}
                        if nrte.table_name in table_names: