Initial Fork from https://bitbucket.org/raphaelmutschler/calibreserver/

lib/sqlalchemy/sql/functions.py

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+# sql/functions.py
+# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: http://www.opensource.org/licenses/mit-license.php
+
+from .. import types as sqltypes, schema
+from .expression import (
+    ClauseList, Function, _literal_as_binds, literal_column, _type_from_args,
+    cast, extract
+    )
+from . import operators
+from .visitors import VisitableType
+from .. import util
+
+_registry = util.defaultdict(dict)
+
+
+def register_function(identifier, fn, package="_default"):
+    """Associate a callable with a particular func. name.
+
+    This is normally called by _GenericMeta, but is also
+    available by itself so that a non-Function construct
+    can be associated with the :data:`.func` accessor (i.e.
+    CAST, EXTRACT).
+
+    """
+    reg = _registry[package]
+    reg[identifier] = fn
+
+
+class _GenericMeta(VisitableType):
+    def __init__(cls, clsname, bases, clsdict):
+        cls.name = name = clsdict.get('name', clsname)
+        cls.identifier = identifier = clsdict.get('identifier', name)
+        package = clsdict.pop('package', '_default')
+        # legacy
+        if '__return_type__' in clsdict:
+            cls.type = clsdict['__return_type__']
+        register_function(identifier, cls, package)
+        super(_GenericMeta, cls).__init__(clsname, bases, clsdict)
+
+
+class GenericFunction(Function):
+    """Define a 'generic' function.
+
+    A generic function is a pre-established :class:`.Function`
+    class that is instantiated automatically when called
+    by name from the :data:`.func` attribute.    Note that
+    calling any name from :data:`.func` has the effect that
+    a new :class:`.Function` instance is created automatically,
+    given that name.  The primary use case for defining
+    a :class:`.GenericFunction` class is so that a function
+    of a particular name may be given a fixed return type.
+    It can also include custom argument parsing schemes as well
+    as additional methods.
+
+    Subclasses of :class:`.GenericFunction` are automatically
+    registered under the name of the class.  For
+    example, a user-defined function ``as_utc()`` would
+    be available immediately::
+
+        from sqlalchemy.sql.functions import GenericFunction
+        from sqlalchemy.types import DateTime
+
+        class as_utc(GenericFunction):
+            type = DateTime
+
+        print select([func.as_utc()])
+
+    User-defined generic functions can be organized into
+    packages by specifying the "package" attribute when defining
+    :class:`.GenericFunction`.   Third party libraries
+    containing many functions may want to use this in order
+    to avoid name conflicts with other systems.   For example,
+    if our ``as_utc()`` function were part of a package
+    "time"::
+
+        class as_utc(GenericFunction):
+            type = DateTime
+            package = "time"
+
+    The above function would be available from :data:`.func`
+    using the package name ``time``::
+
+        print select([func.time.as_utc()])
+
+    A final option is to allow the function to be accessed
+    from one name in :data:`.func` but to render as a different name.
+    The ``identifier`` attribute will override the name used to
+    access the function as loaded from :data:`.func`, but will retain
+    the usage of ``name`` as the rendered name::
+
+        class GeoBuffer(GenericFunction):
+            type = Geometry
+            package = "geo"
+            name = "ST_Buffer"
+            identifier = "buffer"
+
+    The above function will render as follows::
+
+        >>> print func.geo.buffer()
+        ST_Buffer()
+
+    .. versionadded:: 0.8 :class:`.GenericFunction` now supports
+       automatic registration of new functions as well as package
+       and custom naming support.
+
+    .. versionchanged:: 0.8 The attribute name ``type`` is used
+       to specify the function's return type at the class level.
+       Previously, the name ``__return_type__`` was used.  This
+       name is still recognized for backwards-compatibility.
+
+    """
+    __metaclass__ = _GenericMeta
+
+    coerce_arguments = True
+
+    def __init__(self, *args, **kwargs):
+        parsed_args = kwargs.pop('_parsed_args', None)
+        if parsed_args is None:
+            parsed_args = [_literal_as_binds(c) for c in args]
+        self.packagenames = []
+        self._bind = kwargs.get('bind', None)
+        self.clause_expr = ClauseList(
+                operator=operators.comma_op,
+                group_contents=True, *parsed_args).self_group()
+        self.type = sqltypes.to_instance(
+            kwargs.pop("type_", None) or getattr(self, 'type', None))
+
+
+register_function("cast", cast)
+register_function("extract", extract)
+
+
+class next_value(GenericFunction):
+    """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)
+
+
+class ReturnTypeFromArgs(GenericFunction):
+    """Define a function whose return type is the same as its arguments."""
+
+    def __init__(self, *args, **kwargs):
+        args = [_literal_as_binds(c) for c in args]
+        kwargs.setdefault('type_', _type_from_args(args))
+        kwargs['_parsed_args'] = args
+        GenericFunction.__init__(self, *args, **kwargs)
+
+
+class coalesce(ReturnTypeFromArgs):
+    pass
+
+
+class max(ReturnTypeFromArgs):
+    pass
+
+
+class min(ReturnTypeFromArgs):
+    pass
+
+
+class sum(ReturnTypeFromArgs):
+    pass
+
+
+class now(GenericFunction):
+    type = sqltypes.DateTime
+
+
+class concat(GenericFunction):
+    type = sqltypes.String
+
+
+class char_length(GenericFunction):
+    type = sqltypes.Integer
+
+    def __init__(self, arg, **kwargs):
+        GenericFunction.__init__(self, arg, **kwargs)
+
+
+class random(GenericFunction):
+    pass
+
+
+class count(GenericFunction):
+    """The ANSI COUNT aggregate function.  With no arguments,
+    emits COUNT \*.
+
+    """
+    type = sqltypes.Integer
+
+    def __init__(self, expression=None, **kwargs):
+        if expression is None:
+            expression = literal_column('*')
+        GenericFunction.__init__(self, expression, **kwargs)
+
+
+class current_date(AnsiFunction):
+    type = sqltypes.Date
+
+
+class current_time(AnsiFunction):
+    type = sqltypes.Time
+
+
+class current_timestamp(AnsiFunction):
+    type = sqltypes.DateTime
+
+
+class current_user(AnsiFunction):
+    type = sqltypes.String
+
+
+class localtime(AnsiFunction):
+    type = sqltypes.DateTime
+
+
+class localtimestamp(AnsiFunction):
+    type = sqltypes.DateTime
+
+
+class session_user(AnsiFunction):
+    type = sqltypes.String
+
+
+class sysdate(AnsiFunction):
+    type = sqltypes.DateTime
+
+
+class user(AnsiFunction):
+    type = sqltypes.String