diff options
Diffstat (limited to 'lib/sqlalchemy/sql/selectable.py')
| -rw-r--r-- | lib/sqlalchemy/sql/selectable.py | 50 |
1 files changed, 34 insertions, 16 deletions
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py index d59b45fae..7a220f949 100644 --- a/lib/sqlalchemy/sql/selectable.py +++ b/lib/sqlalchemy/sql/selectable.py @@ -24,6 +24,7 @@ from .. import exc from operator import attrgetter from . import operators import operator +import collections from .annotation import Annotated import itertools @@ -682,8 +683,7 @@ class Join(FromClause): providing a "natural join". """ - crit = [] - constraints = set() + constraints = collections.defaultdict(list) for left in (a_subset, a): if left is None: @@ -703,8 +703,7 @@ class Join(FromClause): continue if col is not None: - crit.append(col == fk.parent) - constraints.add(fk.constraint) + constraints[fk.constraint].append((col, fk.parent)) if left is not b: for fk in sorted( left.foreign_keys, @@ -723,12 +722,36 @@ class Join(FromClause): continue if col is not None: - crit.append(col == fk.parent) - constraints.add(fk.constraint) - if crit: + constraints[fk.constraint].append((col, fk.parent)) + if constraints: break - if len(crit) == 0: + 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 = constraints.keys()[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()?" @@ -737,14 +760,9 @@ class Join(FromClause): raise exc.NoForeignKeysError( "Can't find any foreign key relationships " "between '%s' and '%s'.%s" % (a.description, b.description, hint)) - elif 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)) - elif len(crit) == 1: + + crit = [(x == y) for x, y in constraints.values()[0]] + if len(crit) == 1: return (crit[0]) else: return and_(*crit) |