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Diffstat (limited to 'doc/build/changelog/migration_12.rst')
| -rw-r--r-- | doc/build/changelog/migration_12.rst | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/doc/build/changelog/migration_12.rst b/doc/build/changelog/migration_12.rst index e9deb75c4..4ded828c4 100644 --- a/doc/build/changelog/migration_12.rst +++ b/doc/build/changelog/migration_12.rst @@ -812,7 +812,6 @@ if the application is working with plain floats. :ticket:`4020` - .. change_3249: Support for GROUPING SETS, CUBE, ROLLUP @@ -840,6 +839,43 @@ are named in the documentation now:: :ticket:`3429` +.. _change_4075: + +Parameter helper for multi-valued INSERT with contextual default generator +-------------------------------------------------------------------------- + +A default generation function, e.g. that described at +:ref:`context_default_functions`, can look at the current parameters relevant +to the statment via the :attr:`.DefaultExecutionContext.current_parameters` +attribute. However, in the case of a :class:`.Insert` construct that specifies +multiple VALUES clauses via the :meth:`.Insert.values` method, the user-defined +function is called multiple times, once for each parameter set, however there +was no way to know which subset of keys in +:attr:`.DefaultExecutionContext.current_parameters` apply to that column. A +new function :meth:`.DefaultExecutionContext.get_current_parameters` is added, +which includes a keyword argument +:paramref:`.DefaultExecutionContext.get_current_parameters.isolate_multiinsert_groups` +defaulting to ``True``, which performs the extra work of delivering a sub-dictionary of +:attr:`.DefaultExecutionContext.current_parameters` which has the names +localized to the current VALUES clause being processed:: + + + def mydefault(context): + return context.get_current_parameters()['counter'] + 12 + + mytable = Table('mytable', meta, + Column('counter', Integer), + Column('counter_plus_twelve', + Integer, default=mydefault, onupdate=mydefault) + ) + + stmt = mytable.insert().values( + [{"counter": 5}, {"counter": 18}, {"counter": 20}]) + + conn.execute(stmt) + +:ticket:`4075` + Key Behavioral Changes - ORM ============================ |