diff options
Diffstat (limited to 'lib/sqlalchemy/orm/relationships.py')
| -rw-r--r-- | lib/sqlalchemy/orm/relationships.py | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py index 56a33742d..4a6159144 100644 --- a/lib/sqlalchemy/orm/relationships.py +++ b/lib/sqlalchemy/orm/relationships.py @@ -16,6 +16,7 @@ and `secondaryjoin` aspects of :func:`.relationship`. from __future__ import absolute_import from .. import sql, util, exc as sa_exc, schema, log +import weakref from .util import CascadeOptions, _orm_annotate, _orm_deannotate from . import dependency from . import attributes @@ -1532,6 +1533,7 @@ class RelationshipProperty(StrategizedProperty): self._check_cascade_settings(self._cascade) self._post_init() self._generate_backref() + self._join_condition._warn_for_conflicting_sync_targets() super(RelationshipProperty, self).do_init() self._lazy_strategy = self._get_strategy((("lazy", "select"),)) @@ -2519,6 +2521,55 @@ class JoinCondition(object): self.secondary_synchronize_pairs = \ self._deannotate_pairs(secondary_sync_pairs) + _track_sync_targets = weakref.WeakKeyDictionary() + + def _warn_for_conflicting_sync_targets(self): + if not self.support_sync: + return + + # totally complex code that takes place for virtually all + # relationships, detecting an incredibly rare edge case, + # and even then, all just to emit a warning. + # we would like to detect if we are synchronizing any column + # pairs in conflict with another relationship that wishes to sync + # an entirely different column to the same target. This is typically + # when using complex overlapping composite foreign keys. + for from_, to_ in [ + (from_, to_) + for (from_, to_) in self.synchronize_pairs + ] + [ + (from_, to_) for + (from_, to_) in self.secondary_synchronize_pairs + ]: + if to_ not in self._track_sync_targets: + self._track_sync_targets[to_] = weakref.WeakKeyDictionary( + {self.prop: from_}) + else: + other_props = [] + prop_to_from = self._track_sync_targets[to_] + for pr, fr_ in prop_to_from.items(): + if pr.mapper in mapperlib._mapper_registry and \ + fr_ is not from_ and \ + pr not in self.prop._reverse_property: + other_props.append((pr, fr_)) + + if other_props: + util.warn( + "relationship '%s' will copy column %s to column %s, " + "which conflicts with relationship(s): %s. " + "Consider applying " + "viewonly=True to read-only relationships, or provide " + "a primaryjoin condition marking writable columns " + "with the foreign() annotation." % ( + self.prop, + from_, to_, + ", ".join( + "'%s' (copies %s to %s)" % (pr, fr_, to_) + for (pr, fr_) in other_props) + ) + ) + self._track_sync_targets[to_][self.prop] = from_ + @util.memoized_property def remote_columns(self): return self._gather_join_annotations("remote") |