Function find_left_clause_that_matches_given

lib/sqlalchemy/sql/util.py:159–200

Given a list of FROM clauses and a selectable, return the indexes from the list of clauses which is derived from the selectable.

(
    clauses: Sequence[FromClause], join_from: FromClause
)

def find_left_clause_that_matches_given(
    clauses: Sequence[FromClause], join_from: FromClause
) -> List[int]:
    """Given a list of FROM clauses and a selectable,
    return the indexes from the list of
    clauses which is derived from the selectable.

    """

    selectables = list(_from_objects(join_from))
    liberal_idx = []
    for i, f in enumerate(clauses):
        for s in selectables:
            # basic check, if f is derived from s.
            # this can be joins containing a table, or an aliased table
            # or select statement matching to a table.  This check
            # will match a table to a selectable that is adapted from
            # that table.  With Query, this suits the case where a join
            # is being made to an adapted entity
            if f.is_derived_from(s):
                liberal_idx.append(i)
                break

    # in an extremely small set of use cases, a join is being made where
    # there are multiple FROM clauses where our target table is represented
    # in more than one, such as embedded or similar.   in this case, do
    # another pass where we try to get a more exact match where we aren't
    # looking at adaption relationships.
    if len(liberal_idx) > 1:
        conservative_idx = []
        for idx in liberal_idx:
            f = clauses[idx]
            for s in selectables:
                if set(surface_selectables(f)).intersection(
                    surface_selectables(s)
                ):
                    conservative_idx.append(idx)
                    break
        if conservative_idx:
            return conservative_idx

    return liberal_idx


def find_left_clause_to_join_from(