diff options
Diffstat (limited to 'lib/sqlalchemy/sql')
| -rw-r--r-- | lib/sqlalchemy/sql/selectable.py | 97 |
1 files changed, 54 insertions, 43 deletions
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py index 248048662..b4df87e54 100644 --- a/lib/sqlalchemy/sql/selectable.py +++ b/lib/sqlalchemy/sql/selectable.py @@ -746,6 +746,33 @@ class Join(FromClause): providing a "natural join". """ + constraints = cls._joincond_scan_left_right( + a, a_subset, b, consider_as_foreign_keys) + + if len(constraints) > 1: + cls._joincond_trim_constraints( + a, b, constraints, consider_as_foreign_keys) + + if len(constraints) == 0: + if isinstance(b, FromGrouping): + hint = " Perhaps you meant to convert the right side to a "\ + "subquery using alias()?" + else: + hint = "" + raise exc.NoForeignKeysError( + "Can't find any foreign key relationships " + "between '%s' and '%s'.%s" % + (a.description, b.description, hint)) + + crit = [(x == y) for x, y in list(constraints.values())[0]] + if len(crit) == 1: + return (crit[0]) + else: + return and_(*crit) + + @classmethod + def _joincond_scan_left_right( + cls, a, a_subset, b, consider_as_foreign_keys): constraints = collections.defaultdict(list) for left in (a_subset, a): @@ -780,57 +807,41 @@ class Join(FromClause): if nrte.table_name == b.name: raise else: - # this is totally covered. can't get - # coverage to mark it. continue if col is not None: constraints[fk.constraint].append((col, fk.parent)) if constraints: break + return constraints + @classmethod + def _joincond_trim_constraints( + cls, a, b, constraints, consider_as_foreign_keys): + # more than one constraint matched. narrow down the list + # to include just those FKCs that match exactly to + # "consider_as_foreign_keys". + if consider_as_foreign_keys: + for const in list(constraints): + if set(f.parent for f in const.elements) != set( + consider_as_foreign_keys): + del constraints[const] + + # if still multiple constraints, but + # they all refer to the exact same end result, use it. if len(constraints) > 1: - # more than one constraint matched. narrow down the list - # to include just those FKCs that match exactly to - # "consider_as_foreign_keys". - if consider_as_foreign_keys: - for const in list(constraints): - if set(f.parent for f in const.elements) != set( - consider_as_foreign_keys): - del constraints[const] - - # if still multiple constraints, but - # they all refer to the exact same end result, use it. - if len(constraints) > 1: - dedupe = set(tuple(crit) for crit in constraints.values()) - if len(dedupe) == 1: - key = list(constraints)[0] - constraints = {key: constraints[key]} - - if len(constraints) != 1: - raise exc.AmbiguousForeignKeysError( - "Can't determine join between '%s' and '%s'; " - "tables have more than one foreign key " - "constraint relationship between them. " - "Please specify the 'onclause' of this " - "join explicitly." % (a.description, b.description)) - - if len(constraints) == 0: - if isinstance(b, FromGrouping): - hint = " Perhaps you meant to convert the right side to a "\ - "subquery using alias()?" - else: - hint = "" - raise exc.NoForeignKeysError( - "Can't find any foreign key relationships " - "between '%s' and '%s'.%s" % - (a.description, b.description, hint)) - - crit = [(x == y) for x, y in list(constraints.values())[0]] - if len(crit) == 1: - return (crit[0]) - else: - return and_(*crit) + dedupe = set(tuple(crit) for crit in constraints.values()) + if len(dedupe) == 1: + key = list(constraints)[0] + constraints = {key: constraints[key]} + + if len(constraints) != 1: + raise exc.AmbiguousForeignKeysError( + "Can't determine join between '%s' and '%s'; " + "tables have more than one foreign key " + "constraint relationship between them. " + "Please specify the 'onclause' of this " + "join explicitly." % (a.description, b.description)) def select(self, whereclause=None, **kwargs): """Create a :class:`.Select` from this :class:`.Join`. |