diff options
Diffstat (limited to 'lib/sqlalchemy/orm/strategies.py')
| -rw-r--r-- | lib/sqlalchemy/orm/strategies.py | 40 |
1 files changed, 32 insertions, 8 deletions
diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py index b8ab55da4..8b4c4f098 100644 --- a/lib/sqlalchemy/orm/strategies.py +++ b/lib/sqlalchemy/orm/strategies.py @@ -931,6 +931,35 @@ class SubqueryLoader(AbstractRelationshipLoader): q = q.order_by(*eager_order_by) return q + class _SubqCollections(object): + """Given a :class:`.Query` used to emit the "subquery load", + provide a load interface that executes the query at the + first moment a value is needed. + + """ + _data = None + + def __init__(self, subq): + self.subq = subq + + def get(self, key, default): + if self._data is None: + self._load() + return self._data.get(key, default) + + def _load(self): + self._data = dict( + (k, [vv[0] for vv in v]) + for k, v in itertools.groupby( + self.subq, + lambda x: x[1:] + ) + ) + + def loader(self, state, dict_, row): + if self._data is None: + self._load() + def create_row_processor(self, context, path, mapper, row, adapter): if not self.parent.class_manager[self.key].impl.supports_population: @@ -953,12 +982,7 @@ class SubqueryLoader(AbstractRelationshipLoader): # call upon create_row_processor again collections = path.get(context, "collections") if collections is None: - collections = dict( - (k, [v[0] for v in v]) - for k, v in itertools.groupby( - subq, - lambda x: x[1:] - )) + collections = self._SubqCollections(subq) path.set(context, 'collections', collections) if adapter: @@ -978,7 +1002,7 @@ class SubqueryLoader(AbstractRelationshipLoader): state.get_impl(self.key).\ set_committed_value(state, dict_, collection) - return load_collection_from_subq, None, None + return load_collection_from_subq, None, None, collections.loader def _create_scalar_loader(self, collections, local_cols): def load_scalar_from_subq(state, dict_, row): @@ -996,7 +1020,7 @@ class SubqueryLoader(AbstractRelationshipLoader): state.get_impl(self.key).\ set_committed_value(state, dict_, scalar) - return load_scalar_from_subq, None, None + return load_scalar_from_subq, None, None, collections.loader log.class_logger(SubqueryLoader) |