- Added new generic function "next_value()", accepts

a Sequence object as its argument and renders the
appropriate "next value" generation string on the
target platform, if supported.  Also provides
".next_value()" method on Sequence itself.
[ticket:2085]
- added tests for all the conditions described
in [ticket:2085]
- postgresql dialect will exec/compile a Sequence
that has "optional=True".  the optional flag is now only
checked specifically in the context of a Table primary key
evaulation.
- func.next_value() or other SQL expression can
be embedded directly into an insert() construct,
and if implicit or explicit "returning" is used
in conjunction with a primary key column,
the newly generated value will be present in
result.inserted_primary_key. [ticket:2084]

1 files changed, 25 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/functions.py b/lib/sqlalchemy/sql/functions.py
index 10eaa577b..717816656 100644
--- a/lib/sqlalchemy/sql/functions.py
+++ b/lib/sqlalchemy/sql/functions.py
@@ -4,7 +4,7 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: http://www.opensource.org/licenses/mit-license.php
 
-from sqlalchemy import types as sqltypes
+from sqlalchemy import types as sqltypes, schema
 from sqlalchemy.sql.expression import (
     ClauseList, Function, _literal_as_binds, text, _type_from_args
     )
@@ -29,6 +29,29 @@ class GenericFunction(Function):
         self.type = sqltypes.to_instance(
             type_ or getattr(self, '__return_type__', None))
 
+
+class next_value(Function):
+    """Represent the 'next value', given a :class:`.Sequence`
+    as it's single argument.
+    
+    Compiles into the appropriate function on each backend,
+    or will raise NotImplementedError if used on a backend
+    that does not provide support for sequences.
+    
+    """
+    type = sqltypes.Integer()
+    name = "next_value"
+
+    def __init__(self, seq, **kw):
+        assert isinstance(seq, schema.Sequence), \
+                "next_value() accepts a Sequence object as input."
+        self._bind = kw.get('bind', None)
+        self.sequence = seq
+
+    @property
+    def _from_objects(self):
+        return []
+
 class AnsiFunction(GenericFunction):
     def __init__(self, **kwargs):
         GenericFunction.__init__(self, **kwargs)
@@ -52,6 +75,7 @@ class min(ReturnTypeFromArgs):
 class sum(ReturnTypeFromArgs):
     pass
 
+
 class now(GenericFunction):
     __return_type__ = sqltypes.DateTime