Method _join

lib/sqlalchemy/orm/context.py:1907–1998

(self, args, entities_collection)

        return _adapt_clause

    def _join(self, args, entities_collection):
        for right, onclause, from_, flags in args:
            isouter = flags[class="st">"isouter"]
            full = flags[class="st">"full"]

            right = inspect(right)
            if onclause is not None:
                onclause = inspect(onclause)

            if isinstance(right, interfaces.PropComparator):
                if onclause is not None:
                    raise sa_exc.InvalidRequestError(
                        class="st">"No &class="cm">#x27;on clause' argument may be passed when joining "
                        class="st">"to a relationship path as a target"
                    )

                onclause = right
                right = None
            elif class="st">"parententity" in right._annotations:
                right = right._annotations[class="st">"parententity"]

            if onclause is None:
                if not right.is_selectable and not hasattr(right, class="st">"mapper"):
                    raise sa_exc.ArgumentError(
                        class="st">"Expected mapped entity or "
                        class="st">"selectable/table as join target"
                    )

            if isinstance(onclause, interfaces.PropComparator):
                class="cm"># descriptor/property given (or determined); this tells us
                class="cm"># explicitly what the expected class="st">"left" side of the join is.

                of_type = getattr(onclause, class="st">"_of_type", None)

                if right is None:
                    if of_type:
                        right = of_type
                    else:
                        right = onclause.property

                        try:
                            right = right.entity
                        except AttributeError as err:
                            raise sa_exc.ArgumentError(
                                class="st">"Join target %s does not refer to a "
                                class="st">"mapped entity" % right
                            ) from err

                left = onclause._parententity

                prop = onclause.property
                if not isinstance(onclause, attributes.QueryableAttribute):
                    onclause = prop

                class="cm"># check for this path already present.  don't render in that
                class="cm"># case.
                if (left, right, prop.key) in self._already_joined_edges:
                    continue