diff options
Diffstat (limited to 'lib/sqlalchemy/orm/relationships.py')
| -rw-r--r-- | lib/sqlalchemy/orm/relationships.py | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py index 2393df26b..dbc37a4eb 100644 --- a/lib/sqlalchemy/orm/relationships.py +++ b/lib/sqlalchemy/orm/relationships.py @@ -103,6 +103,7 @@ class RelationshipProperty(StrategizedProperty): enable_typechecks=True, join_depth=None, comparator_factory=None, single_parent=False, innerjoin=False, + distinct_target_key=None, doc=None, active_history=False, cascade_backrefs=True, @@ -372,6 +373,27 @@ class RelationshipProperty(StrategizedProperty): or when the reference is one-to-one or a collection that is guaranteed to have one or at least one entry. + :param distinct_target_key=None: + Indicate if a "subquery" eager load should apply the DISTINCT + keyword to the innermost SELECT statement. When left as ``None``, + the DISTINCT keyword will be applied in those cases when the target + columns do not comprise the full primary key of the target table. + When set to ``True``, the DISTINCT keyword is applied to the innermost + SELECT unconditionally. + + It may be desirable to set this flag to False when the DISTINCT is + reducing performance of the innermost subquery beyond that of what + duplicate innermost rows may be causing. + + .. versionadded:: 0.8.3 - distinct_target_key allows the + subquery eager loader to apply a DISTINCT modifier to the + innermost SELECT. + + .. versionchanged:: 0.9.0 - distinct_target_key now defaults to + ``None``, so that the feature enables itself automatically for + those cases where the innermost query targets a non-unique + key. + :param join_depth: when non-``None``, an integer value indicating how many levels deep "eager" loaders should join on a self-referring or cyclical @@ -621,6 +643,7 @@ class RelationshipProperty(StrategizedProperty): self.enable_typechecks = enable_typechecks self.query_class = query_class self.innerjoin = innerjoin + self.distinct_target_key = distinct_target_key self.doc = doc self.active_history = active_history self.join_depth = join_depth |