diff options
Diffstat (limited to 'lib/sqlalchemy/schema.py')
| -rw-r--r-- | lib/sqlalchemy/schema.py | 58 |
1 files changed, 43 insertions, 15 deletions
diff --git a/lib/sqlalchemy/schema.py b/lib/sqlalchemy/schema.py index 70d9013d6..bc3eac213 100644 --- a/lib/sqlalchemy/schema.py +++ b/lib/sqlalchemy/schema.py @@ -750,7 +750,7 @@ class Column(SchemaItem, expression.ColumnClause): if isinstance(self.default, str): # end Py2K util.warn("Unicode column received non-unicode " - "default value.") + "default value.") args.append(ColumnDefault(self.default)) if self.server_default is not None: @@ -1266,7 +1266,16 @@ class ForeignKey(SchemaItem): self.constraint._set_parent_with_dispatch(table) table.foreign_keys.add(self) -class DefaultGenerator(SchemaItem): +class _NotAColumnExpr(object): + def _not_a_column_expr(self): + raise exc.InvalidRequestError( + "This %s cannot be used directly " + "as a column expression." % self.__class__.__name__) + + __clause_element__ = self_group = lambda self: self._not_a_column_expr() + _from_objects = property(lambda self: self._not_a_column_expr()) + +class DefaultGenerator(_NotAColumnExpr, SchemaItem): """Base class for column *default* values.""" __visit_name__ = 'default_generator' @@ -1392,26 +1401,26 @@ class ColumnDefault(DefaultGenerator): class Sequence(DefaultGenerator): """Represents a named database sequence. - + The :class:`.Sequence` object represents the name and configurational parameters of a database sequence. It also represents a construct that can be "executed" by a SQLAlchemy :class:`.Engine` or :class:`.Connection`, rendering the appropriate "next value" function for the target database and returning a result. - + The :class:`.Sequence` is typically associated with a primary key column:: - + some_table = Table('some_table', metadata, Column('id', Integer, Sequence('some_table_seq'), primary_key=True) ) - + When CREATE TABLE is emitted for the above :class:`.Table`, if the target platform supports sequences, a CREATE SEQUENCE statement will be emitted as well. For platforms that don't support sequences, the :class:`.Sequence` construct is ignored. - + See also: :class:`.CreateSequence` :class:`.DropSequence` - + """ __visit_name__ = 'sequence' @@ -1422,7 +1431,7 @@ class Sequence(DefaultGenerator): optional=False, quote=None, metadata=None, for_update=False): """Construct a :class:`.Sequence` object. - + :param name: The name of the sequence. :param start: the starting index of the sequence. This value is used when the CREATE SEQUENCE command is emitted to the database @@ -1455,7 +1464,7 @@ class Sequence(DefaultGenerator): DROP SEQUENCE DDL commands will be emitted corresponding to this :class:`.Sequence` when :meth:`.MetaData.create_all` and :meth:`.MetaData.drop_all` are invoked (new in 0.7). - + Note that when a :class:`.Sequence` is applied to a :class:`.Column`, the :class:`.Sequence` is automatically associated with the :class:`.MetaData` object of that column's parent :class:`.Table`, @@ -1467,7 +1476,7 @@ class Sequence(DefaultGenerator): with a :class:`.Column`, should be invoked for UPDATE statements on that column's table, rather than for INSERT statements, when no value is otherwise present for that column in the statement. - + """ super(Sequence, self).__init__(for_update=for_update) self.name = name @@ -1488,6 +1497,14 @@ class Sequence(DefaultGenerator): def is_clause_element(self): return False + def next_value(self): + """Return a :class:`.next_value` function element + which will render the appropriate increment function + for this :class:`.Sequence` within any SQL expression. + + """ + return expression.func.next_value(self, bind=self.bind) + def __repr__(self): return "Sequence(%s)" % ', '.join( [repr(self.name)] + @@ -1526,8 +1543,16 @@ class Sequence(DefaultGenerator): bind = _bind_or_error(self) bind.drop(self, checkfirst=checkfirst) + def _not_a_column_expr(self): + raise exc.InvalidRequestError( + "This %s cannot be used directly " + "as a column expression. Use func.next_value(sequence) " + "to produce a 'next value' function that's usable " + "as a column element." + % self.__class__.__name__) -class FetchedValue(events.SchemaEventTarget): + +class FetchedValue(_NotAColumnExpr, events.SchemaEventTarget): """A marker for a transparent database-side default. Use :class:`.FetchedValue` when the database is configured @@ -1544,6 +1569,7 @@ class FetchedValue(events.SchemaEventTarget): """ is_server_default = True reflected = False + has_argument = False def __init__(self, for_update=False): self.for_update = for_update @@ -1581,6 +1607,8 @@ class DefaultClause(FetchedValue): """ + has_argument = True + def __init__(self, arg, for_update=False, _reflected=False): util.assert_arg_type(arg, (basestring, expression.ClauseElement, @@ -2508,7 +2536,7 @@ class DDLElement(expression.Executable, expression.ClauseElement): Optional keyword argument - a list of Table objects which are to be created/ dropped within a MetaData.create_all() or drop_all() method call. - + :state: Optional keyword argument - will be the ``state`` argument passed to this function. @@ -2517,13 +2545,13 @@ class DDLElement(expression.Executable, expression.ClauseElement): Keyword argument, will be True if the 'checkfirst' flag was set during the call to ``create()``, ``create_all()``, ``drop()``, ``drop_all()``. - + If the callable returns a true value, the DDL statement will be executed. :param state: any value which will be passed to the callable_ as the ``state`` keyword argument. - + See also: :class:`.DDLEvents` |