a class which extends :class:`.RelationshipProperty.Comparator` which
provides custom SQL clause generation for comparison operations.
+ :param distinct_target_key=False:
+ Indicate if a "subquery" eager load should apply the DISTINCT
+ keyword to the innermost SELECT statement. When set to ``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.
+
+ This flag defaults as False in 0.8 but will default to None in 0.9.
+ 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.
+
:param doc:
docstring which will be applied to the resulting descriptor.
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=False:
- Indicate if a "subquery" eager load should apply the DISTINCT
- keyword to the innermost SELECT statement. When set to ``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.
-
- This flag defaults as False in 0.8 but will default to None in 0.9.
- 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.
-
:param join_depth:
when non-``None``, an integer value indicating how many levels
deep "eager" loaders should join on a self-referring or cyclical