1. Module layout. sql.py and related move into a package called "sql".

2. compiler names changed to be less verbose, unused classes removed.
3. Methods on Dialect which return compilers, schema generators, identifier preparers
have changed to direct class references, typically on the Dialect class itself
or optionally as attributes on an individual Dialect instance if conditional behavior is needed.
This takes away the need for Dialect subclasses to know how to instantiate these
objects, and also reduces method overhead by one call for each one.
4. as a result of 3., some internal signatures have changed for things like compiler() (now statement_compiler()), preparer(), etc., mostly in that the dialect needs to be passed explicitly as the first argument (since they are just class references now).  The compiler() method on Engine and Connection is now also named statement_compiler(), but as before does not take the dialect as an argument.

5. changed _process_row function on RowProxy to be a class reference, cuts out 50K method calls from insertspeed.py

1 files changed, 0 insertions, 3484 deletions

diff --git a/lib/sqlalchemy/sql.py b/lib/sqlalchemy/sql.py
deleted file mode 100644
index 7c73f7cb7..000000000
--- a/lib/sqlalchemy/sql.py
+++ /dev/null
@@ -1,3484 +0,0 @@
-# sql.py
-# Copyright (C) 2005, 2006, 2007 Michael Bayer mike_mp@zzzcomputing.com
-#
-# This module is part of SQLAlchemy and is released under
-# the MIT License: http://www.opensource.org/licenses/mit-license.php
-
-"""Defines the base components of SQL expression trees.
-
-
-All components are derived from a common base class
-[sqlalchemy.sql#ClauseElement].  Common behaviors are organized based
-on class hierarchies, in some cases via mixins.
-
-All object construction from this package occurs via functions which
-in some cases will construct composite ``ClauseElement`` structures
-together, and in other cases simply return a single ``ClauseElement``
-constructed directly.  The function interface affords a more "DSL-ish"
-feel to constructing SQL expressions and also allows future class
-reorganizations.
-
-Even though classes are not constructed directly from the outside,
-most classes which have additional public methods are considered to be
-public (i.e. have no leading underscore).  Other classes which are
-"semi-public" are marked with a single leading underscore; these
-classes usually have few or no public methods and are less guaranteed
-to stay the same in future releases.
-"""
-
-from sqlalchemy import util, exceptions, operators
-from sqlalchemy import types as sqltypes
-import re
-
-__all__ = [
-    'Alias', 'ClauseElement', 'ClauseParameters',
-    'ClauseVisitor', 'ColumnCollection', 'ColumnElement',
-    'CompoundSelect', 'Delete', 'FromClause', 'Insert', 'Join',
-    'Select', 'Selectable', 'TableClause', 'Update', 'alias', 'and_', 'asc',
-    'between', 'bindparam', 'case', 'cast', 'column', 'delete',
-    'desc', 'distinct', 'except_', 'except_all', 'exists', 'extract', 'func',
-    'modifier',
-    'insert', 'intersect', 'intersect_all', 'join', 'literal',
-    'literal_column', 'not_', 'null', 'or_', 'outparam', 'outerjoin', 'select',
-    'subquery', 'table', 'text', 'union', 'union_all', 'update', ]
-
-BIND_PARAMS = re.compile(r'(?<![:\w\x5c]):(\w+)(?!:)', re.UNICODE)
-
-def desc(column):
-    """Return a descending ``ORDER BY`` clause element.
-
-    e.g.::
-
-      order_by = [desc(table1.mycol)]
-    """
-    return _UnaryExpression(column, modifier=operators.desc_op)
-
-def asc(column):
-    """Return an ascending ``ORDER BY`` clause element.
-
-    e.g.::
-
-      order_by = [asc(table1.mycol)]
-    """
-    return _UnaryExpression(column, modifier=operators.asc_op)
-
-def outerjoin(left, right, onclause=None, **kwargs):
-    """Return an ``OUTER JOIN`` clause element.
-
-    The returned object is an instance of [sqlalchemy.sql#Join].
-
-    Similar functionality is also available via the ``outerjoin()``
-    method on any [sqlalchemy.sql#FromClause].
-
-    left
-      The left side of the join.
-
-    right
-      The right side of the join.
-
-    onclause
-      Optional criterion for the ``ON`` clause, is derived from
-      foreign key relationships established between left and right
-      otherwise.
-
-    To chain joins together, use the ``join()`` or ``outerjoin()``
-    methods on the resulting ``Join`` object.
-    """
-
-    return Join(left, right, onclause, isouter = True, **kwargs)
-
-def join(left, right, onclause=None, **kwargs):
-    """Return a ``JOIN`` clause element (regular inner join).
-
-    The returned object is an instance of [sqlalchemy.sql#Join].
-
-    Similar functionality is also available via the ``join()`` method
-    on any [sqlalchemy.sql#FromClause].
-
-    left
-      The left side of the join.
-
-    right
-      The right side of the join.
-
-    onclause
-      Optional criterion for the ``ON`` clause, is derived from
-      foreign key relationships established between left and right
-      otherwise.
-
-    To chain joins together, use the ``join()`` or ``outerjoin()``
-    methods on the resulting ``Join`` object.
-    """
-
-    return Join(left, right, onclause, **kwargs)
-
-def select(columns=None, whereclause=None, from_obj=[], **kwargs):
-    """Returns a ``SELECT`` clause element.
-
-    Similar functionality is also available via the ``select()``
-    method on any [sqlalchemy.sql#FromClause].
-
-    The returned object is an instance of [sqlalchemy.sql#Select].
-
-    All arguments which accept ``ClauseElement`` arguments also accept
-    string arguments, which will be converted as appropriate into
-    either ``text()`` or ``literal_column()`` constructs.
-
-    columns
-      A list of ``ClauseElement`` objects, typically ``ColumnElement``
-      objects or subclasses, which will form the columns clause of the
-      resulting statement.  For all members which are instances of
-      ``Selectable``, the individual ``ColumnElement`` members of the
-      ``Selectable`` will be added individually to the columns clause.
-      For example, specifying a ``Table`` instance will result in all
-      the contained ``Column`` objects within to be added to the
-      columns clause.
-
-      This argument is not present on the form of ``select()``
-      available on ``Table``.
-
-    whereclause
-      A ``ClauseElement`` expression which will be used to form the
-      ``WHERE`` clause.
-
-    from_obj
-      A list of ``ClauseElement`` objects which will be added to the
-      ``FROM`` clause of the resulting statement.  Note that "from"
-      objects are automatically located within the columns and
-      whereclause ClauseElements.  Use this parameter to explicitly
-      specify "from" objects which are not automatically locatable.
-      This could include ``Table`` objects that aren't otherwise
-      present, or ``Join`` objects whose presence will supercede that
-      of the ``Table`` objects already located in the other clauses.
-
-    \**kwargs
-      Additional parameters include:
-
-      prefixes
-        a list of strings or ``ClauseElement`` objects to include
-        directly after the SELECT keyword in the generated statement,
-        for dialect-specific query features.
-
-      distinct=False
-        when ``True``, applies a ``DISTINCT`` qualifier to the columns
-        clause of the resulting statement.
-
-      use_labels=False
-        when ``True``, the statement will be generated using labels
-        for each column in the columns clause, which qualify each
-        column with its parent table's (or aliases) name so that name
-        conflicts between columns in different tables don't occur.
-        The format of the label is <tablename>_<column>.  The "c"
-        collection of the resulting ``Select`` object will use these
-        names as well for targeting column members.
-
-      for_update=False
-        when ``True``, applies ``FOR UPDATE`` to the end of the
-        resulting statement.  Certain database dialects also support
-        alternate values for this parameter, for example mysql
-        supports "read" which translates to ``LOCK IN SHARE MODE``,
-        and oracle supports "nowait" which translates to ``FOR UPDATE
-        NOWAIT``.
-
-      correlate=True
-        indicates that this ``Select`` object should have its
-        contained ``FromClause`` elements "correlated" to an enclosing
-        ``Select`` object.  This means that any ``ClauseElement``
-        instance within the "froms" collection of this ``Select``
-        which is also present in the "froms" collection of an
-        enclosing select will not be rendered in the ``FROM`` clause
-        of this select statement.
-
-      group_by
-        a list of ``ClauseElement`` objects which will comprise the
-        ``GROUP BY`` clause of the resulting select.
-
-      having
-        a ``ClauseElement`` that will comprise the ``HAVING`` clause
-        of the resulting select when ``GROUP BY`` is used.
-
-      order_by
-        a scalar or list of ``ClauseElement`` objects which will
-        comprise the ``ORDER BY`` clause of the resulting select.
-
-      limit=None
-        a numerical value which usually compiles to a ``LIMIT``
-        expression in the resulting select.  Databases that don't
-        support ``LIMIT`` will attempt to provide similar
-        functionality.
-
-      offset=None
-        a numeric value which usually compiles to an ``OFFSET``
-        expression in the resulting select.  Databases that don't
-        support ``OFFSET`` will attempt to provide similar
-        functionality.
-
-      bind=None
-        an ``Engine`` or ``Connection`` instance to which the
-        resulting ``Select ` object will be bound.  The ``Select``
-        object will otherwise automatically bind to whatever
-        ``Connectable`` instances can be located within its contained
-        ``ClauseElement`` members.
-
-      scalar=False
-        deprecated.  Use select(...).as_scalar() to create a "scalar
-        column" proxy for an existing Select object.
-    """
-
-    if 'scalar' in kwargs:
-        util.warn_deprecated('scalar option is deprecated; see docs for details')
-    scalar = kwargs.pop('scalar', False)
-    s = Select(columns, whereclause=whereclause, from_obj=from_obj, **kwargs)
-    if scalar:
-        return s.as_scalar()
-    else:
-        return s
-
-def subquery(alias, *args, **kwargs):
-    """Return an [sqlalchemy.sql#Alias] object derived from a [sqlalchemy.sql#Select].
-
-    name
-      alias name
-
-    \*args, \**kwargs
-
-      all other arguments are delivered to the [sqlalchemy.sql#select()]
-      function.
-    """
-
-    return Select(*args, **kwargs).alias(alias)
-
-def insert(table, values = None, **kwargs):
-    """Return an [sqlalchemy.sql#Insert] clause element.
-
-    Similar functionality is available via the ``insert()`` method on
-    [sqlalchemy.schema#Table].
-
-    table
-      The table to be inserted into.
-
-    values
-      A dictionary which specifies the column specifications of the
-      ``INSERT``, and is optional.  If left as None, the column
-      specifications are determined from the bind parameters used
-      during the compile phase of the ``INSERT`` statement.  If the
-      bind parameters also are None during the compile phase, then the
-      column specifications will be generated from the full list of
-      table columns.
-
-    If both `values` and compile-time bind parameters are present, the
-    compile-time bind parameters override the information specified
-    within `values` on a per-key basis.
-
-    The keys within `values` can be either ``Column`` objects or their
-    string identifiers.  Each key may reference one of:
-
-    * a literal data value (i.e. string, number, etc.);
-    * a Column object;
-    * a SELECT statement.
-
-    If a ``SELECT`` statement is specified which references this
-    ``INSERT`` statement's table, the statement will be correlated
-    against the ``INSERT`` statement.
-    """
-
-    return Insert(table, values, **kwargs)
-
-def update(table, whereclause = None, values = None, **kwargs):
-    """Return an [sqlalchemy.sql#Update] clause element.
-
-    Similar functionality is available via the ``update()`` method on
-    [sqlalchemy.schema#Table].
-
-    table
-      The table to be updated.
-
-    whereclause
-      A ``ClauseElement`` describing the ``WHERE`` condition of the
-      ``UPDATE`` statement.
-
-    values
-      A dictionary which specifies the ``SET`` conditions of the
-      ``UPDATE``, and is optional. If left as None, the ``SET``
-      conditions are determined from the bind parameters used during
-      the compile phase of the ``UPDATE`` statement.  If the bind
-      parameters also are None during the compile phase, then the
-      ``SET`` conditions will be generated from the full list of table
-      columns.
-
-    If both `values` and compile-time bind parameters are present, the
-    compile-time bind parameters override the information specified
-    within `values` on a per-key basis.
-
-    The keys within `values` can be either ``Column`` objects or their
-    string identifiers. Each key may reference one of:
-
-    * a literal data value (i.e. string, number, etc.);
-    * a Column object;
-    * a SELECT statement.
-
-    If a ``SELECT`` statement is specified which references this
-    ``UPDATE`` statement's table, the statement will be correlated
-    against the ``UPDATE`` statement.
-    """
-
-    return Update(table, whereclause, values, **kwargs)
-
-def delete(table, whereclause = None, **kwargs):
-    """Return a [sqlalchemy.sql#Delete] clause element.
-
-    Similar functionality is available via the ``delete()`` method on
-    [sqlalchemy.schema#Table].
-
-    table
-      The table to be updated.
-
-    whereclause
-      A ``ClauseElement`` describing the ``WHERE`` condition of the
-      ``UPDATE`` statement.
-    """
-
-    return Delete(table, whereclause, **kwargs)
-
-def and_(*clauses):
-    """Join a list of clauses together using the ``AND`` operator.
-
-    The ``&`` operator is also overloaded on all
-    [sqlalchemy.sql#_CompareMixin] subclasses to produce the same
-    result.
-    """
-    if len(clauses) == 1:
-        return clauses[0]
-    return ClauseList(operator=operators.and_, *clauses)
-
-def or_(*clauses):
-    """Join a list of clauses together using the ``OR`` operator.
-
-    The ``|`` operator is also overloaded on all
-    [sqlalchemy.sql#_CompareMixin] subclasses to produce the same
-    result.
-    """
-
-    if len(clauses) == 1:
-        return clauses[0]
-    return ClauseList(operator=operators.or_, *clauses)
-
-def not_(clause):
-    """Return a negation of the given clause, i.e. ``NOT(clause)``.
-
-    The ``~`` operator is also overloaded on all
-    [sqlalchemy.sql#_CompareMixin] subclasses to produce the same
-    result.
-    """
-
-    return operators.inv(clause)
-
-def distinct(expr):
-    """Return a ``DISTINCT`` clause."""
-
-    return _UnaryExpression(expr, operator=operators.distinct_op)
-
-def between(ctest, cleft, cright):
-    """Return a ``BETWEEN`` predicate clause.
-
-    Equivalent of SQL ``clausetest BETWEEN clauseleft AND clauseright``.
-
-    The ``between()`` method on all [sqlalchemy.sql#_CompareMixin] subclasses
-    provides similar functionality.
-    """
-
-    ctest = _literal_as_binds(ctest)
-    return _BinaryExpression(ctest, ClauseList(_literal_as_binds(cleft, type_=ctest.type), _literal_as_binds(cright, type_=ctest.type), operator=operators.and_, group=False), operators.between_op)
-
-
-def case(whens, value=None, else_=None):
-    """Produce a ``CASE`` statement.
-
-    whens
-      A sequence of pairs to be translated into "when / then" clauses.
-
-    value
-      Optional for simple case statements.
-
-    else\_
-      Optional as well, for case defaults.
-    """
-
-    whenlist = [ClauseList('WHEN', c, 'THEN', r, operator=None)
-                for (c,r) in whens]
-    if not else_ is None:
-        whenlist.append(ClauseList('ELSE', else_, operator=None))
-    if whenlist:
-        type = list(whenlist[-1])[-1].type
-    else:
-        type = None
-    cc = _CalculatedClause(None, 'CASE', value, type_=type, operator=None, group_contents=False, *whenlist + ['END'])
-    return cc
-
-def cast(clause, totype, **kwargs):
-    """Return a ``CAST`` function.
-
-    Equivalent of SQL ``CAST(clause AS totype)``.
-
-    Use with a [sqlalchemy.types#TypeEngine] subclass, i.e::
-
-      cast(table.c.unit_price * table.c.qty, Numeric(10,4))
-
-    or::
-
-      cast(table.c.timestamp, DATE)
-    """
-
-    return _Cast(clause, totype, **kwargs)
-
-def extract(field, expr):
-    """Return the clause ``extract(field FROM expr)``."""
-
-    expr = _BinaryExpression(text(field), expr, operators.from_)
-    return func.extract(expr)
-
-def exists(*args, **kwargs):
-    """Return an ``EXISTS`` clause as applied to a [sqlalchemy.sql#Select] object.
-
-    The resulting [sqlalchemy.sql#_Exists] object can be executed by
-    itself or used as a subquery within an enclosing select.
-
-    \*args, \**kwargs
-      all arguments are sent directly to the [sqlalchemy.sql#select()]
-      function to produce a ``SELECT`` statement.
-    """
-
-    return _Exists(*args, **kwargs)
-
-def union(*selects, **kwargs):
-    """Return a ``UNION`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    A similar ``union()`` method is available on all
-    [sqlalchemy.sql#FromClause] subclasses.
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-       available keyword arguments are the same as those of
-       [sqlalchemy.sql#select()].
-    """
-
-    return _compound_select('UNION', *selects, **kwargs)
-
-def union_all(*selects, **kwargs):
-    """Return a ``UNION ALL`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    A similar ``union_all()`` method is available on all
-    [sqlalchemy.sql#FromClause] subclasses.
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-      available keyword arguments are the same as those of
-      [sqlalchemy.sql#select()].
-    """
-
-    return _compound_select('UNION ALL', *selects, **kwargs)
-
-def except_(*selects, **kwargs):
-    """Return an ``EXCEPT`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-      available keyword arguments are the same as those of
-      [sqlalchemy.sql#select()].
-    """
-    return _compound_select('EXCEPT', *selects, **kwargs)
-
-def except_all(*selects, **kwargs):
-    """Return an ``EXCEPT ALL`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-      available keyword arguments are the same as those of
-      [sqlalchemy.sql#select()].
-    """
-    return _compound_select('EXCEPT ALL', *selects, **kwargs)
-
-def intersect(*selects, **kwargs):
-    """Return an ``INTERSECT`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-      available keyword arguments are the same as those of
-      [sqlalchemy.sql#select()].
-    """
-    return _compound_select('INTERSECT', *selects, **kwargs)
-
-def intersect_all(*selects, **kwargs):
-    """Return an ``INTERSECT ALL`` of multiple selectables.
-
-    The returned object is an instance of [sqlalchemy.sql#CompoundSelect].
-
-    \*selects
-      a list of [sqlalchemy.sql#Select] instances.
-
-    \**kwargs
-      available keyword arguments are the same as those of
-      [sqlalchemy.sql#select()].
-    """
-    return _compound_select('INTERSECT ALL', *selects, **kwargs)
-
-def alias(selectable, alias=None):
-    """Return an [sqlalchemy.sql#Alias] object.
-
-    An ``Alias`` represents any [sqlalchemy.sql#FromClause] with
-    an alternate name assigned within SQL, typically using the ``AS``
-    clause when generated, e.g. ``SELECT * FROM table AS aliasname``.
-
-    Similar functionality is available via the ``alias()`` method
-    available on all ``FromClause`` subclasses.
-
-      selectable
-        any ``FromClause`` subclass, such as a table, select
-        statement, etc..
-
-      alias
-        string name to be assigned as the alias.  If ``None``, a
-        random name will be generated.
-    """
-
-    return Alias(selectable, alias=alias)
-
-
-def literal(value, type_=None):
-    """Return a literal clause, bound to a bind parameter.
-
-    Literal clauses are created automatically when non-
-    ``ClauseElement`` objects (such as strings, ints, dates, etc.) are
-    used in a comparison operation with a
-    [sqlalchemy.sql#_CompareMixin] subclass, such as a ``Column``
-    object.  Use this function to force the generation of a literal
-    clause, which will be created as a
-    [sqlalchemy.sql#_BindParamClause] with a bound value.
-
-    value
-      the value to be bound.  Can be any Python object supported by
-      the underlying DBAPI, or is translatable via the given type
-      argument.
-
-    type\_
-      an optional [sqlalchemy.types#TypeEngine] which will provide
-      bind-parameter translation for this literal.
-    """
-
-    return _BindParamClause('literal', value, type_=type_, unique=True)
-
-def label(name, obj):
-    """Return a [sqlalchemy.sql#_Label] object for the given [sqlalchemy.sql#ColumnElement].
-
-    A label changes the name of an element in the columns clause of a
-    ``SELECT`` statement, typically via the ``AS`` SQL keyword.
-
-    This functionality is more conveniently available via the
-    ``label()`` method on ``ColumnElement``.
-
-    name
-      label name
-
-    obj
-      a ``ColumnElement``.
-    """
-
-    return _Label(name, obj)
-
-def column(text, type_=None):
-    """Return a textual column clause, as would be in the columns clause of a ``SELECT`` statement.
-
-    The object returned is an instance of [sqlalchemy.sql#_ColumnClause],
-    which represents the "syntactical" portion of the schema-level
-    [sqlalchemy.schema#Column] object.
-
-    text
-      the name of the column.  Quoting rules will be applied to the
-      clause like any other column name.  For textual column
-      constructs that are not to be quoted, use the
-      [sqlalchemy.sql#literal_column()] function.
-
-    type\_
-      an optional [sqlalchemy.types#TypeEngine] object which will
-      provide result-set translation for this column.
-
-    """
-
-    return _ColumnClause(text, type_=type_)
-
-def literal_column(text, type_=None):
-    """Return a textual column clause, as would be in the columns clause of a ``SELECT`` statement.
-
-    The object returned is an instance of [sqlalchemy.sql#_ColumnClause],
-    which represents the "syntactical" portion of the schema-level
-    [sqlalchemy.schema#Column] object.
-
-    text
-      the name of the column.  Quoting rules will not be applied to
-      the column.  For textual column constructs that should be quoted
-      like any other column construct, use the
-      [sqlalchemy.sql#column()] function.
-
-    type
-      an optional [sqlalchemy.types#TypeEngine] object which will
-      provide result-set translation for this column.
-    """
-
-    return _ColumnClause(text, type_=type_, is_literal=True)
-
-def table(name, *columns):
-    """Return a [sqlalchemy.sql#Table] object.
-
-    This is a primitive version of the [sqlalchemy.schema#Table] object,
-    which is a subclass of this object.
-    """
-
-    return TableClause(name, *columns)
-
-def bindparam(key, value=None, type_=None, shortname=None, unique=False):
-    """Create a bind parameter clause with the given key.
-
-    value
-      a default value for this bind parameter.  a bindparam with a
-      value is called a ``value-based bindparam``.
-
-    shortname
-      an ``alias`` for this bind parameter.  usually used to alias the
-      ``key`` nd ``label`` of a column, i.e. ``somecolname`` and
-      ``sometable_somecolname``
-
-    type
-      a sqlalchemy.types.TypeEngine object indicating the type of this
-      bind param, will invoke type-specific bind parameter processing
-
-    unique
-      if True, bind params sharing the same name will have their
-      underlying ``key`` modified to a uniquely generated name.
-      mostly useful with value-based bind params.
-    """
-
-    if isinstance(key, _ColumnClause):
-        return _BindParamClause(key.name, value, type_=key.type, shortname=shortname, unique=unique)
-    else:
-        return _BindParamClause(key, value, type_=type_, shortname=shortname, unique=unique)
-
-def outparam(key, type_=None):
-    """Create an 'OUT' parameter for usage in functions (stored procedures), for databases which support them.
-
-    The ``outparam`` can be used like a regular function parameter.
-    The "output" value will be available from the
-    [sqlalchemy.engine#ResultProxy] object via its ``out_parameters``
-    attribute, which returns a dictionary containing the values.
-    """
-
-    return _BindParamClause(key, None, type_=type_, unique=False, isoutparam=True)
-
-def text(text, bind=None, *args, **kwargs):
-    """Create literal text to be inserted into a query.
-
-    When constructing a query from a ``select()``, ``update()``,
-    ``insert()`` or ``delete()``, using plain strings for argument
-    values will usually result in text objects being created
-    automatically.  Use this function when creating textual clauses
-    outside of other ``ClauseElement`` objects, or optionally wherever
-    plain text is to be used.
-
-    text
-      the text of the SQL statement to be created.  use ``:<param>``
-      to specify bind parameters; they will be compiled to their
-      engine-specific format.
-
-    bind
-      an optional connection or engine to be used for this text query.
-
-    bindparams
-      a list of ``bindparam()`` instances which can be used to define
-      the types and/or initial values for the bind parameters within
-      the textual statement; the keynames of the bindparams must match
-      those within the text of the statement.  The types will be used
-      for pre-processing on bind values.
-
-    typemap
-      a dictionary mapping the names of columns represented in the
-      ``SELECT`` clause of the textual statement to type objects,
-      which will be used to perform post-processing on columns within
-      the result set (for textual statements that produce result
-      sets).
-    """
-
-    return _TextClause(text, bind=bind, *args, **kwargs)
-
-def null():
-    """Return a ``_Null`` object, which compiles to ``NULL`` in a sql statement."""
-
-    return _Null()
-
-class _FunctionGenerator(object):
-    """Generate ``_Function`` objects based on getattr calls."""
-
-    def __init__(self, **opts):
-        self.__names = []
-        self.opts = opts
-
-    def __getattr__(self, name):
-        # passthru __ attributes; fixes pydoc
-        if name.startswith('__'):
-            try:
-                return self.__dict__[name]
-            except KeyError:
-                raise AttributeError(name)
-
-        elif name.startswith('_'):
-            name = name[0:-1]
-        f = _FunctionGenerator(**self.opts)
-        f.__names = list(self.__names) + [name]
-        return f
-
-    def __call__(self, *c, **kwargs):
-        o = self.opts.copy()
-        o.update(kwargs)
-        return _Function(self.__names[-1], packagenames=self.__names[0:-1], *c, **o)
-
-func = _FunctionGenerator()
-
-# TODO: use UnaryExpression for this instead ?
-modifier = _FunctionGenerator(group=False)
-
-
-def _compound_select(keyword, *selects, **kwargs):
-    return CompoundSelect(keyword, *selects, **kwargs)
-
-def _is_literal(element):
-    return not isinstance(element, ClauseElement)
-
-def _literal_as_text(element):
-    if isinstance(element, Operators):
-        return element.expression_element()
-    elif _is_literal(element):
-        return _TextClause(unicode(element))
-    else:
-        return element
-
-def _literal_as_column(element):
-    if isinstance(element, Operators):
-        return element.clause_element()
-    elif _is_literal(element):
-        return literal_column(str(element))
-    else:
-        return element
-
-def _literal_as_binds(element, name='literal', type_=None):
-    if isinstance(element, Operators):
-        return element.expression_element()
-    elif _is_literal(element):
-        if element is None:
-            return null()
-        else:
-            return _BindParamClause(name, element, shortname=name, type_=type_, unique=True)
-    else:
-        return element
-
-def _selectable(element):
-    if hasattr(element, '__selectable__'):
-        return element.__selectable__()
-    elif isinstance(element, Selectable):
-        return element
-    else:
-        raise exceptions.ArgumentError("Object '%s' is not a Selectable and does not implement `__selectable__()`" % repr(element))
-
-def is_column(col):
-    """True if ``col`` is an instance of ``ColumnElement``."""
-    return isinstance(col, ColumnElement)
-
-class ClauseParameters(object):
-    """Represent a dictionary/iterator of bind parameter key names/values.
-
-    Tracks the original [sqlalchemy.sql#_BindParamClause] objects
-    as well as the keys/position of each parameter, and can return
-    parameters as a dictionary or a list.  Will process parameter
-    values according to the ``TypeEngine`` objects present in the
-    ``_BindParamClause`` instances.
-    """
-
-    def __init__(self, dialect, positional=None):
-        self.dialect = dialect
-        self.__binds = {}
-        self.positional = positional or []
-
-    def get_parameter(self, key):
-        return self.__binds[key]
-
-    def set_parameter(self, bindparam, value, name):
-        self.__binds[name] = [bindparam, name, value]
-
-    def get_original(self, key):
-        return self.__binds[key][2]
-
-    def get_type(self, key):
-        return self.__binds[key][0].type
-
-    def get_processors(self):
-        """return a dictionary of bind 'processing' functions"""
-        return dict([
-            (key, value) for key, value in
-            [(
-                key,
-                self.__binds[key][0].bind_processor(self.dialect)
-            ) for key in self.__binds]
-            if value is not None
-        ])
-
-    def get_processed(self, key, processors):
-        return key in processors and processors[key](self.__binds[key][2]) or self.__binds[key][2]
-
-    def keys(self):
-        return self.__binds.keys()
-
-    def __iter__(self):
-        return iter(self.keys())
-
-    def __getitem__(self, key):
-        (bind, name, value) = self.__binds[key]
-        processor = bind.bind_processor(self.dialect)
-        return processor is not None and processor(value) or value
-
-    def __contains__(self, key):
-        return key in self.__binds
-
-    def set_value(self, key, value):
-        self.__binds[key][2] = value
-
-    def get_original_dict(self):
-        return dict([(name, value) for (b, name, value) in self.__binds.values()])
-
-    def __get_processed(self, key, processors):
-        if key in processors:
-            return processors[key](self.__binds[key][2])
-        else:
-            return self.__binds[key][2]
-
-    def get_raw_list(self, processors):
-        return [self.__get_processed(key, processors) for key in self.positional]
-
-    def get_raw_dict(self, processors, encode_keys=False):
-        if encode_keys:
-            return dict([
-                (
-                    key.encode(self.dialect.encoding),
-                    self.__get_processed(key, processors)
-                )
-                for key in self.keys()
-            ])
-        else:
-            return dict([
-                (
-                    key,
-                    self.__get_processed(key, processors)
-                )
-                for key in self.keys()
-            ])
-
-    def __repr__(self):
-        return self.__class__.__name__ + ":" + repr(self.get_original_dict())
-
-class ClauseVisitor(object):
-    """A class that knows how to traverse and visit ``ClauseElements``.
-
-    Calls visit_XXX() methods dynamically generated for each
-    particualr ``ClauseElement`` subclass encountered.  Traversal of a
-    hierarchy of ``ClauseElements`` is achieved via the ``traverse()``
-    method, which is passed the lead ``ClauseElement``.
-
-    By default, ``ClauseVisitor`` traverses all elements fully.
-    Options can be specified at the class level via the
-    ``__traverse_options__`` dictionary which will be passed to the
-    ``get_children()`` method of each ``ClauseElement``; these options
-    can indicate modifications to the set of elements returned, such
-    as to not return column collections (column_collections=False) or
-    to return Schema-level items (schema_visitor=True).
-
-    ``ClauseVisitor`` also supports a simultaneous copy-and-traverse
-    operation, which will produce a copy of a given ``ClauseElement``
-    structure while at the same time allowing ``ClauseVisitor``
-    subclasses to modify the new structure in-place.
-    """
-
-    __traverse_options__ = {}
-
-    def traverse_single(self, obj, **kwargs):
-        meth = getattr(self, "visit_%s" % obj.__visit_name__, None)
-        if meth:
-            return meth(obj, **kwargs)
-
-    def iterate(self, obj, stop_on=None):
-        stack = [obj]
-        traversal = []
-        while len(stack) > 0:
-            t = stack.pop()
-            if stop_on is None or t not in stop_on:
-                yield t
-                traversal.insert(0, t)
-                for c in t.get_children(**self.__traverse_options__):
-                    stack.append(c)
-
-    def traverse(self, obj, stop_on=None, clone=False):
-        if clone:
-            obj = obj._clone()
-
-        stack = [obj]
-        traversal = []
-        while len(stack) > 0:
-            t = stack.pop()
-            if stop_on is None or t not in stop_on:
-                traversal.insert(0, t)
-                if clone:
-                    t._copy_internals()
-                for c in t.get_children(**self.__traverse_options__):
-                    stack.append(c)
-        for target in traversal:
-            v = self
-            while v is not None:
-                meth = getattr(v, "visit_%s" % target.__visit_name__, None)
-                if meth:
-                    meth(target)
-                v = getattr(v, '_next', None)
-        return obj
-
-    def chain(self, visitor):
-        """'chain' an additional ClauseVisitor onto this ClauseVisitor.
-
-        The chained visitor will receive all visit events after this one.
-        """
-
-        tail = self
-        while getattr(tail, '_next', None) is not None:
-            tail = tail._next
-        tail._next = visitor
-        return self
-
-class NoColumnVisitor(ClauseVisitor):
-    """A ClauseVisitor that will not traverse exported column collections.
-
-    Will not traverse the exported Column collections on Table, Alias,
-    Select, and CompoundSelect objects (i.e. their 'columns' or 'c'
-    attribute).
-
-    This is useful because most traversals don't need those columns,
-    or in the case of ANSICompiler it traverses them explicitly; so
-    skipping their traversal here greatly cuts down on method call
-    overhead.
-    """
-
-    __traverse_options__ = {'column_collections': False}
-
-
-class _FigureVisitName(type):
-    def __init__(cls, clsname, bases, dict):
-        if not '__visit_name__' in cls.__dict__:
-            m = re.match(r'_?(\w+?)(?:Expression|Clause|Element|$)', clsname)
-            x = m.group(1)
-            x = re.sub(r'(?!^)[A-Z]', lambda m:'_'+m.group(0).lower(), x)
-            cls.__visit_name__ = x.lower()
-        super(_FigureVisitName, cls).__init__(clsname, bases, dict)
-
-class ClauseElement(object):
-    """Base class for elements of a programmatically constructed SQL expression."""
-    __metaclass__ = _FigureVisitName
-
-    def _clone(self):
-        """Create a shallow copy of this ClauseElement.
-
-        This method may be used by a generative API.  Its also used as
-        part of the "deep" copy afforded by a traversal that combines
-        the _copy_internals() method.
-        """
-
-        c = self.__class__.__new__(self.__class__)
-        c.__dict__ = self.__dict__.copy()
-        return c
-
-    def _get_from_objects(self, **modifiers):
-        """Return objects represented in this ``ClauseElement`` that
-        should be added to the ``FROM`` list of a query, when this
-        ``ClauseElement`` is placed in the column clause of a
-        ``Select`` statement.
-        """
-
-        raise NotImplementedError(repr(self))
-
-    def _hide_froms(self, **modifiers):
-        """Return a list of ``FROM`` clause elements which this ``ClauseElement`` replaces."""
-
-        return []
-
-    def unique_params(self, *optionaldict, **kwargs):
-        """Return a copy with ``bindparam()`` elments replaced.
-
-        Same functionality as ``params()``, except adds `unique=True`
-        to affected bind parameters so that multiple statements can be
-        used.
-        """
-
-        return self._params(True, optionaldict, kwargs)
-    def params(self, *optionaldict, **kwargs):
-        """Return a copy with ``bindparam()`` elments replaced.
-
-        Returns a copy of this ClauseElement with ``bindparam()``
-        elements replaced with values taken from the given dictionary::
-
-          >>> clause = column('x') + bindparam('foo')
-          >>> print clause.compile().params
-          {'foo':None}
-          >>> print clause.params({'foo':7}).compile().params
-          {'foo':7}
-        """
-
-        return self._params(False, optionaldict, kwargs)
-
-    def _params(self, unique, optionaldict, kwargs):
-        if len(optionaldict) == 1:
-            kwargs.update(optionaldict[0])
-        elif len(optionaldict) > 1:
-            raise exceptions.ArgumentError("params() takes zero or one positional dictionary argument")
-
-        class Vis(ClauseVisitor):
-            def visit_bindparam(self, bind):
-                if bind.key in kwargs:
-                    bind.value = kwargs[bind.key]
-                if unique:
-                    bind.unique=True
-        return Vis().traverse(self, clone=True)
-
-    def compare(self, other):
-        """Compare this ClauseElement to the given ClauseElement.
-
-        Subclasses should override the default behavior, which is a
-        straight identity comparison.
-        """
-
-        return self is other
-
-    def _copy_internals(self):
-        """Reassign internal elements to be clones of themselves.
-
-        Called during a copy-and-traverse operation on newly
-        shallow-copied elements to create a deep copy.
-        """
-
-        pass
-
-    def get_children(self, **kwargs):
-        """Return immediate child elements of this ``ClauseElement``.
-
-        This is used for visit traversal.
-
-        \**kwargs may contain flags that change the collection that is
-        returned, for example to return a subset of items in order to
-        cut down on larger traversals, or to return child items from a
-        different context (such as schema-level collections instead of
-        clause-level).
-        """
-        return []
-
-    def self_group(self, against=None):
-        return self
-
-    def supports_execution(self):
-        """Return True if this clause element represents a complete executable statement."""
-
-        return False
-
-    def _find_engine(self):
-        """Default strategy for locating an engine within the clause element.
-
-        Relies upon a local engine property, or looks in the *from*
-        objects which ultimately have to contain Tables or
-        TableClauses.
-        """
-
-        try:
-            if self._bind is not None:
-                return self._bind
-        except AttributeError:
-            pass
-        for f in self._get_from_objects():
-            if f is self:
-                continue
-            engine = f.bind
-            if engine is not None:
-                return engine
-        else:
-            return None
-
-    bind = property(lambda s:s._find_engine(), doc="""Returns the Engine or Connection to which this ClauseElement is bound, or None if none found.""")
-
-    def execute(self, *multiparams, **params):
-        """Compile and execute this ``ClauseElement``."""
-
-        if multiparams:
-            compile_params = multiparams[0]
-        else:
-            compile_params = params
-        return self.compile(bind=self.bind, parameters=compile_params).execute(*multiparams, **params)
-
-    def scalar(self, *multiparams, **params):
-        """Compile and execute this ``ClauseElement``, returning the result's scalar representation."""
-
-        return self.execute(*multiparams, **params).scalar()
-
-    def compile(self, bind=None, parameters=None, compiler=None, dialect=None):
-        """Compile this SQL expression.
-
-        Uses the given ``Compiler``, or the given ``AbstractDialect``
-        or ``Engine`` to create a ``Compiler``.  If no `compiler`
-        arguments are given, tries to use the underlying ``Engine``
-        this ``ClauseElement`` is bound to to create a ``Compiler``,
-        if any.
-
-        Finally, if there is no bound ``Engine``, uses an
-        ``ANSIDialect`` to create a default ``Compiler``.
-
-        `parameters` is a dictionary representing the default bind
-        parameters to be used with the statement.  If `parameters` is
-        a list, it is assumed to be a list of dictionaries and the
-        first dictionary in the list is used with which to compile
-        against.
-
-        The bind parameters can in some cases determine the output of
-        the compilation, such as for ``UPDATE`` and ``INSERT``
-        statements the bind parameters that are present determine the
-        ``SET`` and ``VALUES`` clause of those statements.
-        """
-
-        if isinstance(parameters, (list, tuple)):
-            parameters = parameters[0]
-
-        if compiler is None:
-            if dialect is not None:
-                compiler = dialect.compiler(self, parameters)
-            elif bind is not None:
-                compiler = bind.compiler(self, parameters)
-            elif self.bind is not None:
-                compiler = self.bind.compiler(self, parameters)
-
-        if compiler is None:
-            import sqlalchemy.ansisql as ansisql
-            compiler = ansisql.ANSIDialect().compiler(self, parameters=parameters)
-        compiler.compile()
-        return compiler
-
-    def __str__(self):
-        return unicode(self.compile()).encode('ascii', 'backslashreplace')
-
-    def __and__(self, other):
-        return and_(self, other)
-
-    def __or__(self, other):
-        return or_(self, other)
-
-    def __invert__(self):
-        return self._negate()
-
-    def _negate(self):
-        if hasattr(self, 'negation_clause'):
-            return self.negation_clause
-        else:
-            return _UnaryExpression(self.self_group(against=operators.inv), operator=operators.inv, negate=None)
-
-
-class Operators(object):
-    def __and__(self, other):
-        return self.operate(operators.and_, other)
-
-    def __or__(self, other):
-        return self.operate(operators.or_, other)
-
-    def __invert__(self):
-        return self.operate(operators.inv)
-
-    def clause_element(self):
-        raise NotImplementedError()
-
-    def operate(self, op, *other, **kwargs):
-        raise NotImplementedError()
-
-    def reverse_operate(self, op, other, **kwargs):
-        raise NotImplementedError()
-
-class ColumnOperators(Operators):
-    """Defines comparison and math operations."""
-
-    def __lt__(self, other):
-        return self.operate(operators.lt, other)
-
-    def __le__(self, other):
-        return self.operate(operators.le, other)
-
-    def __eq__(self, other):
-        return self.operate(operators.eq, other)
-
-    def __ne__(self, other):
-        return self.operate(operators.ne, other)
-
-    def __gt__(self, other):
-        return self.operate(operators.gt, other)
-
-    def __ge__(self, other):
-        return self.operate(operators.ge, other)
-
-    def concat(self, other):
-        return self.operate(operators.concat_op, other)
-
-    def like(self, other):
-        return self.operate(operators.like_op, other)
-
-    def in_(self, *other):
-        return self.operate(operators.in_op, other)
-
-    def startswith(self, other):
-        return self.operate(operators.startswith_op, other)
-
-    def endswith(self, other):
-        return self.operate(operators.endswith_op, other)
-
-    def desc(self):
-        return self.operate(operators.desc_op)
-
-    def asc(self):
-        return self.operate(operators.asc_op)
-
-    def __radd__(self, other):
-        return self.reverse_operate(operators.add, other)
-
-    def __rsub__(self, other):
-        return self.reverse_operate(operators.sub, other)
-
-    def __rmul__(self, other):
-        return self.reverse_operate(operators.mul, other)
-
-    def __rdiv__(self, other):
-        return self.reverse_operate(operators.div, other)
-
-    def between(self, cleft, cright):
-        return self.operate(operators.between_op, cleft, cright)
-
-    def distinct(self):
-        return self.operate(operators.distinct_op)
-
-    def __add__(self, other):
-        return self.operate(operators.add, other)
-
-    def __sub__(self, other):
-        return self.operate(operators.sub, other)
-
-    def __mul__(self, other):
-        return self.operate(operators.mul, other)
-
-    def __div__(self, other):
-        return self.operate(operators.div, other)
-
-    def __mod__(self, other):
-        return self.operate(operators.mod, other)
-
-    def __truediv__(self, other):
-        return self.operate(operators.truediv, other)
-
-# precedence ordering for common operators.  if an operator is not
-# present in this list, it will be parenthesized when grouped against
-# other operators
-_smallest = object()
-_largest = object()
-
-PRECEDENCE = {
-    operators.from_:15,
-    operators.mul:7,
-    operators.div:7,
-    operators.mod:7,
-    operators.add:6,
-    operators.sub:6,
-    operators.concat_op:6,
-    operators.ilike_op:5,
-    operators.notilike_op:5,
-    operators.like_op:5,
-    operators.notlike_op:5,
-    operators.in_op:5,
-    operators.notin_op:5,
-    operators.is_:5,
-    operators.isnot:5,
-    operators.eq:5,
-    operators.ne:5,
-    operators.gt:5,
-    operators.lt:5,
-    operators.ge:5,
-    operators.le:5,
-    operators.between_op:5,
-    operators.distinct_op:5,
-    operators.inv:4,
-    operators.and_:3,
-    operators.or_:2,
-    operators.comma_op:-1,
-    operators.as_:-1,
-    operators.exists:0,
-    _smallest: -1000,
-    _largest: 1000
-}
-
-class _CompareMixin(ColumnOperators):
-    """Defines comparison and math operations for ``ClauseElement`` instances."""
-
-    def __compare(self, op, obj, negate=None):
-        if obj is None or isinstance(obj, _Null):
-            if op == operators.eq:
-                return _BinaryExpression(self.expression_element(), null(), operators.is_, negate=operators.isnot)
-            elif op == operators.ne:
-                return _BinaryExpression(self.expression_element(), null(), operators.isnot, negate=operators.is_)
-            else:
-                raise exceptions.ArgumentError("Only '='/'!=' operators can be used with NULL")
-        else:
-            obj = self._check_literal(obj)
-        return _BinaryExpression(self.expression_element(), obj, op, type_=sqltypes.Boolean, negate=negate)
-
-    def __operate(self, op, obj):
-        obj = self._check_literal(obj)
-
-        type_ = self._compare_type(obj)
-
-        # TODO: generalize operator overloading like this out into the
-        # types module
-        if op == operators.add and isinstance(type_, (sqltypes.Concatenable)):
-            op = operators.concat_op
-        return _BinaryExpression(self.expression_element(), obj, op, type_=type_)
-    operators = {
-        operators.add : (__operate,),
-        operators.mul : (__operate,),
-        operators.sub : (__operate,),
-        operators.div : (__operate,),
-        operators.mod : (__operate,),
-        operators.truediv : (__operate,),
-        operators.lt : (__compare, operators.ge),
-        operators.le : (__compare, operators.gt),
-        operators.ne : (__compare, operators.eq),
-        operators.gt : (__compare, operators.le),
-        operators.ge : (__compare, operators.lt),
-        operators.eq : (__compare, operators.ne),
-        operators.like_op : (__compare, operators.notlike_op),
-    }
-
-    def operate(self, op, *other):
-        o = _CompareMixin.operators[op]
-        return o[0](self, op, other[0], *o[1:])
-
-    def reverse_operate(self, op, other):
-        return self._bind_param(other).operate(op, self)
-
-    def in_(self, *other):
-        return self._in_impl(operators.in_op, operators.notin_op, *other)
-
-    def _in_impl(self, op, negate_op, *other):
-        if len(other) == 0:
-            return _Grouping(case([(self.__eq__(None), text('NULL'))], else_=text('0')).__eq__(text('1')))
-        elif len(other) == 1:
-            o = other[0]
-            if _is_literal(o) or isinstance( o, _CompareMixin):
-                return self.__eq__( o)    #single item -> ==
-            else:
-                assert isinstance(o, Selectable)
-                return self.__compare( op, o, negate=negate_op)   #single selectable
-
-        args = []
-        for o in other:
-            if not _is_literal(o):
-                if not isinstance( o, _CompareMixin):
-                    raise exceptions.InvalidRequestError( "in() function accepts either non-selectable values, or a single selectable: "+repr(o) )
-            else:
-                o = self._bind_param(o)
-            args.append(o)
-        return self.__compare(op, ClauseList(*args).self_group(against=op), negate=negate_op)
-
-    def startswith(self, other):
-        """Produce the clause ``LIKE '<other>%'``"""
-
-        perc = isinstance(other,(str,unicode)) and '%' or literal('%',type_= sqltypes.String)
-        return self.__compare(operators.like_op, other + perc)
-
-    def endswith(self, other):
-        """Produce the clause ``LIKE '%<other>'``"""
-
-        if isinstance(other,(str,unicode)): po = '%' + other
-        else:
-            po = literal('%', type_=sqltypes.String) + other
-            po.type = sqltypes.to_instance(sqltypes.String)     #force!
-        return self.__compare(operators.like_op, po)
-
-    def label(self, name):
-        """Produce a column label, i.e. ``<columnname> AS <name>``"""
-        return _Label(name, self, self.type)
-
-    def desc(self):
-        """Produce a DESC clause, i.e. ``<columnname> DESC``"""
-
-        return desc(self)
-
-    def asc(self):
-        """Produce a ASC clause, i.e. ``<columnname> ASC``"""
-
-        return asc(self)
-
-    def distinct(self):
-        """Produce a DISTINCT clause, i.e. ``DISTINCT <columnname>``"""
-        return _UnaryExpression(self, operator=operators.distinct_op)
-
-    def between(self, cleft, cright):
-        """Produce a BETWEEN clause, i.e. ``<column> BETWEEN <cleft> AND <cright>``"""
-
-        return _BinaryExpression(self, ClauseList(self._check_literal(cleft), self._check_literal(cright), operator=operators.and_, group=False), operators.between_op)
-
-    def op(self, operator):
-        """produce a generic operator function.
-
-        e.g.::
-
-          somecolumn.op("*")(5)
-
-        produces::
-
-          somecolumn * 5
-
-        operator
-          a string which will be output as the infix operator between
-          this ``ClauseElement`` and the expression passed to the
-          generated function.
-        """
-        return lambda other: self.__operate(operator, other)
-
-    def _bind_param(self, obj):
-        return _BindParamClause('literal', obj, shortname=None, type_=self.type, unique=True)
-
-    def _check_literal(self, other):
-        if isinstance(other, Operators):
-            return other.expression_element()
-        elif _is_literal(other):
-            return self._bind_param(other)
-        else:
-            return other
-
-    def clause_element(self):
-        """Allow ``_CompareMixins`` to return the underlying ``ClauseElement``, for non-``ClauseElement`` ``_CompareMixins``."""
-        return self
-
-    def expression_element(self):
-        """Allow ``_CompareMixins`` to return the appropriate object to be used in expressions."""
-
-        return self
-
-    def _compare_type(self, obj):
-        """Allow subclasses to override the type used in constructing
-        ``_BinaryExpression`` objects.
-
-        Default return value is the type of the given object.
-        """
-
-        return obj.type
-
-class Selectable(ClauseElement):
-    """Represent a column list-holding object.
-
-    This is the common base class of [sqlalchemy.sql#ColumnElement]
-    and [sqlalchemy.sql#FromClause].  The reason ``ColumnElement`` is
-    marked as a "list-holding" object is so that it can be treated
-    similarly to ``FromClause`` in column-selection scenarios; it
-    contains a list of columns consisting of itself.
-    """
-
-    columns = util.NotImplProperty("""a [sqlalchemy.sql#ColumnCollection] containing ``ColumnElement`` instances.""")
-
-    def select(self, whereclauses = None, **params):
-        return select([self], whereclauses, **params)
-
-class ColumnElement(ClauseElement, _CompareMixin):
-    """Represent an element that is usable within the "column clause" portion of a ``SELECT`` statement.
-
-    This includes columns associated with tables, aliases, and
-    subqueries, expressions, function calls, SQL keywords such as
-    ``NULL``, literals, etc.  ``ColumnElement`` is the ultimate base
-    class for all such elements.
-
-    ``ColumnElement`` supports the ability to be a *proxy* element,
-    which indicates that the ``ColumnElement`` may be associated with
-    a ``Selectable`` which was derived from another ``Selectable``.
-    An example of a "derived" ``Selectable`` is an ``Alias`` of a
-    ``Table``.
-
-    A ``ColumnElement``, by subclassing the ``_CompareMixin`` mixin
-    class, provides the ability to generate new ``ClauseElement``
-    objects using Python expressions.  See the ``_CompareMixin``
-    docstring for more details.
-    """
-
-    primary_key = property(lambda self:getattr(self, '_primary_key', False),
-                           doc=\
-        """Primary key flag.  Indicates if this ``Column`` represents part or 
-        whole of a primary key for its parent table.
-        """)
-    foreign_keys = property(lambda self:getattr(self, '_foreign_keys', []),
-                            doc=\
-        """Foreign key accessor.  References a list of ``ForeignKey`` objects 
-        which each represent a foreign key placed on this column's ultimate
-        ancestor.
-        """)
-
-    def _one_fkey(self):
-        if self._foreign_keys:
-            return list(self._foreign_keys)[0]
-        else:
-            return None
-
-    foreign_key = property(_one_fkey)
-
-    def _get_orig_set(self):
-        try:
-            return self.__orig_set
-        except AttributeError:
-            self.__orig_set = util.Set([self])
-            return self.__orig_set
-
-    def _set_orig_set(self, s):
-        if len(s) == 0:
-            s.add(self)
-        self.__orig_set = s
-
-    orig_set = property(_get_orig_set, _set_orig_set,
-                        doc=\
-        """A Set containing TableClause-bound, non-proxied ColumnElements 
-        for which this ColumnElement is a proxy.  In all cases except 
-        for a column proxied from a Union (i.e. CompoundSelect), this 
-        set will be just one element.
-        """)
-
-    def shares_lineage(self, othercolumn):
-        """Return True if the given ``ColumnElement`` has a common ancestor to this ``ColumnElement``.
-        """
-
-        for c in self.orig_set:
-            if c in othercolumn.orig_set:
-                return True
-        else:
-            return False
-
-    def _make_proxy(self, selectable, name=None):
-        """Create a new ``ColumnElement`` representing this
-        ``ColumnElement`` as it appears in the select list of a
-        descending selectable.
-
-        The default implementation returns a ``_ColumnClause`` if a
-        name is given, else just returns self.
-        """
-
-        if name is not None:
-            co = _ColumnClause(name, selectable)
-            co.orig_set = self.orig_set
-            selectable.columns[name]= co
-            return co
-        else:
-            return self
-
-class ColumnCollection(util.OrderedProperties):
-    """An ordered dictionary that stores a list of ColumnElement
-    instances.
-
-    Overrides the ``__eq__()`` method to produce SQL clauses between
-    sets of correlated columns.
-    """
-
-    def __init__(self, *cols):
-        super(ColumnCollection, self).__init__()
-        [self.add(c) for c in cols]
-
-    def __str__(self):
-        return repr([str(c) for c in self])
-
-    def add(self, column):
-        """Add a column to this collection.
-
-        The key attribute of the column will be used as the hash key
-        for this dictionary.
-        """
-
-        # Allow an aliased column to replace an unaliased column of the
-        # same name.
-        if column.name in self:
-            other = self[column.name]
-            if other.name == other.key:
-                del self[other.name]
-        self[column.key] = column
-
-    def remove(self, column):
-        del self[column.key]
-
-    def extend(self, iter):
-        for c in iter:
-            self.add(c)
-
-    def __eq__(self, other):
-        l = []
-        for c in other:
-            for local in self:
-                if c.shares_lineage(local):
-                    l.append(c==local)
-        return and_(*l)
-
-    def __contains__(self, other):
-        if not isinstance(other, basestring):
-            raise exceptions.ArgumentError("__contains__ requires a string argument")
-        return util.OrderedProperties.__contains__(self, other)
-
-    def contains_column(self, col):
-        # have to use a Set here, because it will compare the identity
-        # of the column, not just using "==" for comparison which will always return a
-        # "True" value (i.e. a BinaryClause...)
-        return col in util.Set(self)
-
-class ColumnSet(util.OrderedSet):
-    def contains_column(self, col):
-        return col in self
-
-    def extend(self, cols):
-        for col in cols:
-            self.add(col)
-
-    def __add__(self, other):
-        return list(self) + list(other)
-
-    def __eq__(self, other):
-        l = []
-        for c in other:
-            for local in self:
-                if c.shares_lineage(local):
-                    l.append(c==local)
-        return and_(*l)
-
-class FromClause(Selectable):
-    """Represent an element that can be used within the ``FROM`` clause of a ``SELECT`` statement."""
-
-    __visit_name__ = 'fromclause'
-
-    def __init__(self, name=None):
-        self.name = name
-
-    def _get_from_objects(self, **modifiers):
-        # this could also be [self], at the moment it doesnt matter to the Select object
-        return []
-
-    def default_order_by(self):
-        return [self.oid_column]
-
-    def count(self, whereclause=None, **params):
-        if self.primary_key:
-            col = list(self.primary_key)[0]
-        else:
-            col = list(self.columns)[0]
-        return select([func.count(col).label('tbl_row_count')], whereclause, from_obj=[self], **params)
-
-    def join(self, right, *args, **kwargs):
-        return Join(self, right, *args, **kwargs)
-
-    def outerjoin(self, right, *args, **kwargs):
-        return Join(self, right, isouter=True, *args, **kwargs)
-
-    def alias(self, name=None):
-        return Alias(self, name)
-
-    def named_with_column(self):
-        """True if the name of this FromClause may be prepended to a
-        column in a generated SQL statement.
-        """
-
-        return False
-
-    def _locate_oid_column(self):
-        """Subclasses should override this to return an appropriate OID column."""
-
-        return None
-
-    def _get_oid_column(self):
-        if not hasattr(self, '_oid_column'):
-            self._oid_column = self._locate_oid_column()
-        return self._oid_column
-
-    def _get_all_embedded_columns(self):
-        ret = []
-        class FindCols(ClauseVisitor):
-            def visit_column(self, col):
-                ret.append(col)
-        FindCols().traverse(self)
-        return ret
-
-    def is_derived_from(self, fromclause):
-        """Return True if this FromClause is 'derived' from the given FromClause.
-
-        An example would be an Alias of a Table is derived from that Table.
-        """
-
-        return False
-
-    def replace_selectable(self, old, alias):
-      """replace all occurences of FromClause 'old' with the given Alias object, returning a copy of this ``FromClause``."""
-
-      from sqlalchemy import sql_util
-      return sql_util.ClauseAdapter(alias).traverse(self, clone=True)
-
-    def corresponding_column(self, column, raiseerr=True, keys_ok=False, require_embedded=False):
-        """Given a ``ColumnElement``, return the exported ``ColumnElement``
-        object from this ``Selectable`` which corresponds to that
-        original ``Column`` via a common anscestor column.
-
-        column
-          the target ``ColumnElement`` to be matched
-
-        raiseerr
-          if True, raise an error if the given ``ColumnElement`` could
-          not be matched. if False, non-matches will return None.
-
-        keys_ok
-          if the ``ColumnElement`` cannot be matched, attempt to match
-          based on the string "key" property of the column alone. This
-          makes the search much more liberal.
-
-        require_embedded
-          only return corresponding columns for the given
-          ``ColumnElement``, if the given ``ColumnElement`` is
-          actually present within a sub-element of this
-          ``FromClause``.  Normally the column will match if it merely
-          shares a common anscestor with one of the exported columns
-          of this ``FromClause``.
-        """
-
-        if self.c.contains_column(column):
-            return column
-
-        if require_embedded and column not in util.Set(self._get_all_embedded_columns()):
-            if not raiseerr:
-                return None
-            else:
-                raise exceptions.InvalidRequestError("Column instance '%s' is not directly present within selectable '%s'" % (str(column), column.table))
-        for c in column.orig_set:
-            try:
-                return self.original_columns[c]
-            except KeyError:
-                pass
-        else:
-            if keys_ok:
-                try:
-                    return self.c[column.name]
-                except KeyError:
-                    pass
-            if not raiseerr:
-                return None
-            else:
-                raise exceptions.InvalidRequestError("Given column '%s', attached to table '%s', failed to locate a corresponding column from table '%s'" % (str(column), str(getattr(column, 'table', None)), self.name))
-
-    def _get_exported_attribute(self, name):
-        try:
-            return getattr(self, name)
-        except AttributeError:
-            self._export_columns()
-            return getattr(self, name)
-
-    def _clone_from_clause(self):
-        # delete all the "generated" collections of columns for a
-        # newly cloned FromClause, so that they will be re-derived
-        # from the item.  this is because FromClause subclasses, when
-        # cloned, need to reestablish new "proxied" columns that are
-        # linked to the new item
-        for attr in ('_columns', '_primary_key' '_foreign_keys', '_orig_cols', '_oid_column'):
-            if hasattr(self, attr):
-                delattr(self, attr)
-
-    columns = property(lambda s:s._get_exported_attribute('_columns'))
-    c = property(lambda s:s._get_exported_attribute('_columns'))
-    primary_key = property(lambda s:s._get_exported_attribute('_primary_key'))
-    foreign_keys = property(lambda s:s._get_exported_attribute('_foreign_keys'))
-    original_columns = property(lambda s:s._get_exported_attribute('_orig_cols'), doc=\
-        """A dictionary mapping an original Table-bound 
-        column to a proxied column in this FromClause.
-        """)
-    oid_column = property(_get_oid_column)
-
-    def _export_columns(self, columns=None):
-        """Initialize column collections.
-
-        The collections include the primary key, foreign keys, list of
-        all columns, as well as the *_orig_cols* collection which is a
-        dictionary used to match Table-bound columns to proxied
-        columns in this ``FromClause``.  The columns in each
-        collection are *proxied* from the columns returned by the
-        _exportable_columns method, where a *proxied* column maintains
-        most or all of the properties of its original column, except
-        its parent ``Selectable`` is this ``FromClause``.
-        """
-
-        if hasattr(self, '_columns') and columns is None:
-            # TODO: put a mutex here ?  this is a key place for threading probs
-            return
-        self._columns = ColumnCollection()
-        self._primary_key = ColumnSet()
-        self._foreign_keys = util.Set()
-        self._orig_cols = {}
-
-        if columns is None:
-            columns = self._flatten_exportable_columns()
-        for co in columns:
-            cp = self._proxy_column(co)
-            for ci in cp.orig_set:
-                cx = self._orig_cols.get(ci)
-                # TODO: the '=' thing here relates to the order of
-                # columns as they are placed in the "columns"
-                # collection of a CompositeSelect, illustrated in
-                # test/sql/selectable.SelectableTest.testunion make
-                # this relationship less brittle
-                if cx is None or cp._distance <= cx._distance:
-                    self._orig_cols[ci] = cp
-        if self.oid_column is not None:
-            for ci in self.oid_column.orig_set:
-                self._orig_cols[ci] = self.oid_column
-
-    def _flatten_exportable_columns(self):
-        """Return the list of ColumnElements represented within this FromClause's _exportable_columns"""
-        export = self._exportable_columns()
-        for column in export:
-            if isinstance(column, Selectable):
-                for co in column.columns:
-                    yield co
-            elif isinstance(column, ColumnElement):
-                yield column
-            else:
-                continue
-
-    def _exportable_columns(self):
-        return []
-
-    def _proxy_column(self, column):
-        return column._make_proxy(self)
-
-class _BindParamClause(ClauseElement, _CompareMixin):
-    """Represent a bind parameter.
-
-    Public constructor is the ``bindparam()`` function.
-    """
-
-    __visit_name__ = 'bindparam'
-
-    def __init__(self, key, value, shortname=None, type_=None, unique=False, isoutparam=False):
-        """Construct a _BindParamClause.
-
-        key
-          the key for this bind param.  Will be used in the generated
-          SQL statement for dialects that use named parameters.  This
-          value may be modified when part of a compilation operation,
-          if other ``_BindParamClause`` objects exist with the same
-          key, or if its length is too long and truncation is
-          required.
-
-        value
-          Initial value for this bind param.  This value may be
-          overridden by the dictionary of parameters sent to statement
-          compilation/execution.
-
-        shortname
-          Defaults to the key, a *short name* that will also identify
-          this bind parameter, similar to an alias.  the bind
-          parameter keys sent to a statement compilation or compiled
-          execution may match either the key or the shortname of the
-          corresponding ``_BindParamClause`` objects.
-
-        type\_
-          A ``TypeEngine`` object that will be used to pre-process the
-          value corresponding to this ``_BindParamClause`` at
-          execution time.
-
-        unique
-          if True, the key name of this BindParamClause will be
-          modified if another ``_BindParamClause`` of the same name
-          already has been located within the containing
-          ``ClauseElement``.
-
-        isoutparam
-          if True, the parameter should be treated like a stored procedure "OUT"
-          parameter.
-        """
-
-        self.key = key or "{ANON %d param}" % id(self)
-        self.value = value
-        self.shortname = shortname or key
-        self.unique = unique
-        self.isoutparam = isoutparam
-        type_ = sqltypes.to_instance(type_)
-        if isinstance(type_, sqltypes.NullType) and type(value) in _BindParamClause.type_map:
-            self.type = sqltypes.to_instance(_BindParamClause.type_map[type(value)])
-        else:
-            self.type = type_
-
-    # TODO: move to types module, obviously
-    type_map = {
-        str : sqltypes.String,
-        unicode : sqltypes.Unicode,
-        int : sqltypes.Integer,
-        float : sqltypes.Numeric
-    }
-
-    def _get_from_objects(self, **modifiers):
-        return []
-
-    def bind_processor(self, dialect):
-        return self.type.dialect_impl(dialect).bind_processor(dialect)
-
-    def _compare_type(self, obj):
-        if not isinstance(self.type, sqltypes.NullType):
-            return self.type
-        else:
-            return obj.type
-
-    def compare(self, other):
-        """Compare this ``_BindParamClause`` to the given clause.
-
-        Since ``compare()`` is meant to compare statement syntax, this
-        method returns True if the two ``_BindParamClauses`` have just
-        the same type.
-        """
-
-        return isinstance(other, _BindParamClause) and other.type.__class__ == self.type.__class__
-
-    def __repr__(self):
-        return "_BindParamClause(%s, %s, type_=%s)" % (repr(self.key), repr(self.value), repr(self.type))
-
-class _TypeClause(ClauseElement):
-    """Handle a type keyword in a SQL statement.
-
-    Used by the ``Case`` statement.
-    """
-
-    __visit_name__ = 'typeclause'
-
-    def __init__(self, type):
-        self.type = type
-
-    def _get_from_objects(self, **modifiers):
-        return []
-
-class _TextClause(ClauseElement):
-    """Represent a literal SQL text fragment.
-
-    Public constructor is the ``text()`` function.
-    """
-
-    __visit_name__ = 'textclause'
-
-    def __init__(self, text = "", bind=None, bindparams=None, typemap=None):
-        self._bind = bind
-        self.bindparams = {}
-        self.typemap = typemap
-        if typemap is not None:
-            for key in typemap.keys():
-                typemap[key] = sqltypes.to_instance(typemap[key])
-
-        def repl(m):
-            self.bindparams[m.group(1)] = bindparam(m.group(1))
-            return ":%s" % m.group(1)
-
-        # scan the string and search for bind parameter names, add them
-        # to the list of bindparams
-        self.text = BIND_PARAMS.sub(repl, text)
-        if bindparams is not None:
-            for b in bindparams:
-                self.bindparams[b.key] = b
-
-    def _get_type(self):
-        if self.typemap is not None and len(self.typemap) == 1:
-            return list(self.typemap)[0]
-        else:
-            return None
-    type = property(_get_type)
-
-    columns = property(lambda s:[])
-
-    def _copy_internals(self):
-        self.bindparams = [b._clone() for b in self.bindparams]
-
-    def get_children(self, **kwargs):
-        return self.bindparams.values()
-
-    def _get_from_objects(self, **modifiers):
-        return []
-
-    def supports_execution(self):
-        return True
-
-    def _table_iterator(self):
-        return iter([])
-
-class _Null(ColumnElement):
-    """Represent the NULL keyword in a SQL statement.
-
-    Public constructor is the ``null()`` function.
-    """
-
-    def __init__(self):
-        self.type = sqltypes.NULLTYPE
-
-    def _get_from_objects(self, **modifiers):
-        return []
-
-class ClauseList(ClauseElement):
-    """Describe a list of clauses, separated by an operator.
-
-    By default, is comma-separated, such as a column listing.
-    """
-    __visit_name__ = 'clauselist'
-
-    def __init__(self, *clauses, **kwargs):
-        self.clauses = []
-        self.operator = kwargs.pop('operator', operators.comma_op)
-        self.group = kwargs.pop('group', True)
-        self.group_contents = kwargs.pop('group_contents', True)
-        for c in clauses:
-            if c is None: 
-                continue
-            self.append(c)
-
-    def __iter__(self):
-        return iter(self.clauses)
-    def __len__(self):
-        return len(self.clauses)
-
-    def append(self, clause):
-        # TODO: not sure if i like the 'group_contents' flag.  need to
-        # define the difference between a ClauseList of ClauseLists,
-        # and a "flattened" ClauseList of ClauseLists.  flatten()
-        # method ?
-        if self.group_contents:
-            self.clauses.append(_literal_as_text(clause).self_group(against=self.operator))
-        else:
-            self.clauses.append(_literal_as_text(clause))
-
-    def _copy_internals(self):
-        self.clauses = [clause._clone() for clause in self.clauses]
-
-    def get_children(self, **kwargs):
-        return self.clauses
-
-    def _get_from_objects(self, **modifiers):
-        f = []
-        for c in self.clauses:
-            f += c._get_from_objects(**modifiers)
-        return f
-
-    def self_group(self, against=None):
-        if self.group and self.operator != against and PRECEDENCE.get(self.operator, PRECEDENCE[_smallest]) <= PRECEDENCE.get(against, PRECEDENCE[_largest]):
-            return _Grouping(self)
-        else:
-            return self
-
-    def compare(self, other):
-        """Compare this ``ClauseList`` to the given ``ClauseList``,
-        including a comparison of all the clause items.
-        """
-
-        if not isinstance(other, ClauseList) and len(self.clauses) == 1:
-            return self.clauses[0].compare(other)
-        elif isinstance(other, ClauseList) and len(self.clauses) == len(other.clauses):
-            for i in range(0, len(self.clauses)):
-                if not self.clauses[i].compare(other.clauses[i]):
-                    return False
-            else:
-                return self.operator == other.operator
-        else:
-            return False
-
-class _CalculatedClause(ColumnElement):
-    """Describe a calculated SQL expression that has a type, like ``CASE``.
-
-    Extends ``ColumnElement`` to provide column-level comparison
-    operators.
-    """
-
-    __visit_name__ = 'calculatedclause'
-
-    def __init__(self, name, *clauses, **kwargs):
-        self.name = name
-        self.type = sqltypes.to_instance(kwargs.get('type_', None))
-        self._bind = kwargs.get('bind', None)
-        self.group = kwargs.pop('group', True)
-        clauses = ClauseList(operator=kwargs.get('operator', None), group_contents=kwargs.get('group_contents', True), *clauses)
-        if self.group:
-            self.clause_expr = clauses.self_group()
-        else:
-            self.clause_expr = clauses
-
-    key = property(lambda self:self.name or "_calc_")
-
-    def _copy_internals(self):
-        self.clause_expr = self.clause_expr._clone()
-
-    def clauses(self):
-        if isinstance(self.clause_expr, _Grouping):
-            return self.clause_expr.elem
-        else:
-            return self.clause_expr
-    clauses = property(clauses)
-
-    def get_children(self, **kwargs):
-        return self.clause_expr,
-
-    def _get_from_objects(self, **modifiers):
-        return self.clauses._get_from_objects(**modifiers)
-
-    def _bind_param(self, obj):
-        return _BindParamClause(self.name, obj, type_=self.type, unique=True)
-
-    def select(self):
-        return select([self])
-
-    def scalar(self):
-        return select([self]).execute().scalar()
-
-    def execute(self):
-        return select([self]).execute()
-
-    def _compare_type(self, obj):
-        return self.type
-
-class _Function(_CalculatedClause, FromClause):
-    """Describe a SQL function.
-
-    Extends ``_CalculatedClause``, turn the *clauselist* into function
-    arguments, also adds a `packagenames` argument.
-    """
-
-    def __init__(self, name, *clauses, **kwargs):
-        self.packagenames = kwargs.get('packagenames', None) or []
-        kwargs['operator'] = operators.comma_op
-        _CalculatedClause.__init__(self, name, **kwargs)
-        for c in clauses:
-            self.append(c)
-
-    key = property(lambda self:self.name)
-    columns = property(lambda self:[self])
-
-    def _copy_internals(self):
-        _CalculatedClause._copy_internals(self)
-        self._clone_from_clause()
-
-    def get_children(self, **kwargs):
-        return _CalculatedClause.get_children(self, **kwargs)
-
-    def append(self, clause):
-        self.clauses.append(_literal_as_binds(clause, self.name))
-
-
-class _Cast(ColumnElement):
-
-    def __init__(self, clause, totype, **kwargs):
-        if not hasattr(clause, 'label'):
-            clause = literal(clause)
-        self.type = sqltypes.to_instance(totype)
-        self.clause = clause
-        self.typeclause = _TypeClause(self.type)
-        self._distance = 0
-
-    def _copy_internals(self):
-        self.clause = self.clause._clone()
-        self.typeclause = self.typeclause._clone()
-
-    def get_children(self, **kwargs):
-        return self.clause, self.typeclause
-
-    def _get_from_objects(self, **modifiers):
-        return self.clause._get_from_objects(**modifiers)
-
-    def _make_proxy(self, selectable, name=None):
-        if name is not None:
-            co = _ColumnClause(name, selectable, type_=self.type)
-            co._distance = self._distance + 1
-            co.orig_set = self.orig_set
-            selectable.columns[name]= co
-            return co
-        else:
-            return self
-
-
-class _UnaryExpression(ColumnElement):
-    def __init__(self, element, operator=None, modifier=None, type_=None, negate=None):
-        self.operator = operator
-        self.modifier = modifier
-
-        self.element = _literal_as_text(element).self_group(against=self.operator or self.modifier)
-        self.type = sqltypes.to_instance(type_)
-        self.negate = negate
-
-    def _get_from_objects(self, **modifiers):
-        return self.element._get_from_objects(**modifiers)
-
-    def _copy_internals(self):
-        self.element = self.element._clone()
-
-    def get_children(self, **kwargs):
-        return self.element,
-
-    def compare(self, other):
-        """Compare this ``_UnaryExpression`` against the given ``ClauseElement``."""
-
-        return (
-            isinstance(other, _UnaryExpression) and
-            self.operator == other.operator and
-            self.modifier == other.modifier and 
-            self.element.compare(other.element)
-        )
-
-    def _negate(self):
-        if self.negate is not None:
-            return _UnaryExpression(self.element, operator=self.negate, negate=self.operator, modifier=self.modifier, type_=self.type)
-        else:
-            return super(_UnaryExpression, self)._negate()
-
-    def self_group(self, against):
-        if self.operator and PRECEDENCE.get(self.operator, PRECEDENCE[_smallest]) <= PRECEDENCE.get(against, PRECEDENCE[_largest]):
-            return _Grouping(self)
-        else:
-            return self
-
-
-class _BinaryExpression(ColumnElement):
-    """Represent an expression that is ``LEFT <operator> RIGHT``."""
-
-    def __init__(self, left, right, operator, type_=None, negate=None):
-        self.left = _literal_as_text(left).self_group(against=operator)
-        self.right = _literal_as_text(right).self_group(against=operator)
-        self.operator = operator
-        self.type = sqltypes.to_instance(type_)
-        self.negate = negate
-
-    def _get_from_objects(self, **modifiers):
-        return self.left._get_from_objects(**modifiers) + self.right._get_from_objects(**modifiers)
-
-    def _copy_internals(self):
-        self.left = self.left._clone()
-        self.right = self.right._clone()
-
-    def get_children(self, **kwargs):
-        return self.left, self.right
-
-    def compare(self, other):
-        """Compare this ``_BinaryExpression`` against the given ``_BinaryExpression``."""
-
-        return (
-            isinstance(other, _BinaryExpression) and
-            self.operator == other.operator and
-            (
-                self.left.compare(other.left) and
-                self.right.compare(other.right) or
-                (
-                    self.operator in [operators.eq, operators.ne,
-                                      operators.add, operators.mul] and
-                    self.left.compare(other.right) and
-                    self.right.compare(other.left)
-                )
-            )
-        )
-
-    def self_group(self, against=None):
-        # use small/large defaults for comparison so that unknown
-        # operators are always parenthesized
-        if self.operator != against and (PRECEDENCE.get(self.operator, PRECEDENCE[_smallest]) <= PRECEDENCE.get(against, PRECEDENCE[_largest])):
-            return _Grouping(self)
-        else:
-            return self
-
-    def _negate(self):
-        if self.negate is not None:
-            return _BinaryExpression(self.left, self.right, self.negate, negate=self.operator, type_=self.type)
-        else:
-            return super(_BinaryExpression, self)._negate()
-
-class _Exists(_UnaryExpression):
-    __visit_name__ = _UnaryExpression.__visit_name__
-
-    def __init__(self, *args, **kwargs):
-        kwargs['correlate'] = True
-        s = select(*args, **kwargs).as_scalar().self_group()
-        _UnaryExpression.__init__(self, s, operator=operators.exists)
-
-    def select(self, whereclauses = None, **params):
-        return select([self], whereclauses, **params)
-
-    def correlate(self, fromclause):
-        e = self._clone()
-        e.element = self.element.correlate(fromclause).self_group()
-        return e
-
-    def where(self, clause):
-        e = self._clone()
-        e.element = self.element.where(clause).self_group()
-        return e
-
-    def _hide_froms(self, **modifiers):
-        return self._get_from_objects(**modifiers)
-
-class Join(FromClause):
-    """represent a ``JOIN`` construct between two ``FromClause`` elements.
-
-    The public constructor function for ``Join`` is the module-level
-    ``join()`` function, as well as the ``join()`` method available
-    off all ``FromClause`` subclasses.
-    """
-
-    def __init__(self, left, right, onclause=None, isouter = False):
-        self.left = _selectable(left)
-        self.right = _selectable(right).self_group()
-        if onclause is None:
-            self.onclause = self._match_primaries(self.left, self.right)
-        else:
-            self.onclause = onclause
-        self.isouter = isouter
-        self.__folded_equivalents = None
-        self._init_primary_key()
-
-    name = property(lambda s: "Join object on " + s.left.name + " " + s.right.name)
-    encodedname = property(lambda s: s.name.encode('ascii', 'backslashreplace'))
-
-    def _init_primary_key(self):
-        pkcol = util.Set([c for c in self._flatten_exportable_columns() if c.primary_key])
-
-        equivs = {}
-        def add_equiv(a, b):
-            for x, y in ((a, b), (b, a)):
-                if x in equivs:
-                    equivs[x].add(y)
-                else:
-                    equivs[x] = util.Set([y])
-
-        class BinaryVisitor(ClauseVisitor):
-            def visit_binary(self, binary):
-                if binary.operator == operators.eq:
-                    add_equiv(binary.left, binary.right)
-        BinaryVisitor().traverse(self.onclause)
-
-        for col in pkcol:
-            for fk in col.foreign_keys:
-                if fk.column in pkcol:
-                    add_equiv(col, fk.column)
-
-        omit = util.Set()
-        for col in pkcol:
-            p = col
-            for c in equivs.get(col, util.Set()):
-                if p.references(c) or (c.primary_key and not p.primary_key):
-                    omit.add(p)
-                    p = c
-
-        self.__primary_key = ColumnSet([c for c in self._flatten_exportable_columns() if c.primary_key and c not in omit])
-
-    primary_key = property(lambda s:s.__primary_key)
-
-    def self_group(self, against=None):
-        return _FromGrouping(self)
-
-    def _locate_oid_column(self):
-        return self.left.oid_column
-
-    def _exportable_columns(self):
-        return [c for c in self.left.columns] + [c for c in self.right.columns]
-
-    def _proxy_column(self, column):
-        self._columns[column._label] = column
-        for f in column.foreign_keys:
-            self._foreign_keys.add(f)
-        return column
-
-    def _copy_internals(self):
-        self._clone_from_clause()
-        self.left = self.left._clone()
-        self.right = self.right._clone()
-        self.onclause = self.onclause._clone()
-        self.__folded_equivalents = None
-        self._init_primary_key()
-
-    def get_children(self, **kwargs):
-        return self.left, self.right, self.onclause
-
-    def _match_primaries(self, primary, secondary):
-        crit = []
-        constraints = util.Set()
-        for fk in secondary.foreign_keys:
-            if fk.references(primary):
-                crit.append(primary.corresponding_column(fk.column) == fk.parent)
-                constraints.add(fk.constraint)
-                self.foreignkey = fk.parent
-        if primary is not secondary:
-            for fk in primary.foreign_keys:
-                if fk.references(secondary):
-                    crit.append(secondary.corresponding_column(fk.column) == fk.parent)
-                    constraints.add(fk.constraint)
-                    self.foreignkey = fk.parent
-        if len(crit) == 0:
-            raise exceptions.ArgumentError(
-                "Can't find any foreign key relationships "
-                "between '%s' and '%s'" % (primary.name, secondary.name))
-        elif len(constraints) > 1:
-            raise exceptions.ArgumentError(
-                "Can't determine join between '%s' and '%s'; "
-                "tables have more than one foreign key "
-                "constraint relationship between them. "
-                "Please specify the 'onclause' of this "
-                "join explicitly." % (primary.name, secondary.name))
-        elif len(crit) == 1:
-            return (crit[0])
-        else:
-            return and_(*crit)
-
-    def _get_folded_equivalents(self, equivs=None):
-        if self.__folded_equivalents is not None:
-            return self.__folded_equivalents
-        if equivs is None:
-            equivs = util.Set()
-        class LocateEquivs(NoColumnVisitor):
-            def visit_binary(self, binary):
-                if binary.operator == operators.eq and binary.left.name == binary.right.name:
-                    equivs.add(binary.right)
-                    equivs.add(binary.left)
-        LocateEquivs().traverse(self.onclause)
-        collist = []
-        if isinstance(self.left, Join):
-            left = self.left._get_folded_equivalents(equivs)
-        else:
-            left = list(self.left.columns)
-        if isinstance(self.right, Join):
-            right = self.right._get_folded_equivalents(equivs)
-        else:
-            right = list(self.right.columns)
-        used = util.Set()
-        for c in left + right:
-            if c in equivs:
-                if c.name not in used:
-                    collist.append(c)
-                    used.add(c.name)
-            else: 
-                collist.append(c)
-        self.__folded_equivalents = collist
-        return self.__folded_equivalents
-
-    folded_equivalents = property(_get_folded_equivalents, doc="Returns the column list of this Join with all equivalently-named, "
-                                                            "equated columns folded into one column, where 'equated' means they are "
-                                                            "equated to each other in the ON clause of this join.")
-
-    def select(self, whereclause = None, fold_equivalents=False, **kwargs):
-        """Create a ``Select`` from this ``Join``.
-
-        whereclause
-          the WHERE criterion that will be sent to the ``select()``
-          function
-
-        fold_equivalents
-          based on the join criterion of this ``Join``, do not include
-          repeat column names in the column list of the resulting
-          select, for columns that are calculated to be "equivalent"
-          based on the join criterion of this ``Join``. This will
-          recursively apply to any joins directly nested by this one
-          as well.
-
-        \**kwargs
-          all other kwargs are sent to the underlying ``select()`` function.
-          See the ``select()`` module level function for details.
-        """
-
-        if fold_equivalents:
-            collist = self.folded_equivalents
-        else:
-            collist = [self.left, self.right]
-
-        return select(collist, whereclause, from_obj=[self], **kwargs)
-
-    bind = property(lambda s:s.left.bind or s.right.bind)
-
-    def alias(self, name=None):
-        """Create a ``Select`` out of this ``Join`` clause and return an ``Alias`` of it.
-
-        The ``Select`` is not correlating.
-        """
-
-        return self.select(use_labels=True, correlate=False).alias(name)
-
-    def _hide_froms(self, **modifiers):
-        return self.left._get_from_objects(**modifiers) + self.right._get_from_objects(**modifiers)
-
-    def _get_from_objects(self, **modifiers):
-        return [self] + self.onclause._get_from_objects(**modifiers) + self.left._get_from_objects(**modifiers) + self.right._get_from_objects(**modifiers)
-
-class Alias(FromClause):
-    """Represents an table or selectable alias (AS).
-
-    Represents an alias, as typically applied to any table or
-    sub-select within a SQL statement using the ``AS`` keyword (or
-    without the keyword on certain databases such as Oracle).
-
-    This object is constructed from the ``alias()`` module level
-    function as well as the ``alias()`` method available on all
-    ``FromClause`` subclasses.
-    """
-
-    def __init__(self, selectable, alias=None):
-        baseselectable = selectable
-        while isinstance(baseselectable, Alias):
-            baseselectable = baseselectable.selectable
-        self.original = baseselectable
-        self.selectable = selectable
-        if alias is None:
-            if self.original.named_with_column():
-                alias = getattr(self.original, 'name', None)
-            alias = '{ANON %d %s}' % (id(self), alias or 'anon')
-        self.name = alias
-        self.encodedname = alias.encode('ascii', 'backslashreplace')
-
-    def is_derived_from(self, fromclause):
-        x = self.selectable
-        while True:
-            if x is fromclause:
-                return True
-            if isinstance(x, Alias):
-                x = x.selectable
-            else:
-                break
-        return False
-
-    def supports_execution(self):
-        return self.original.supports_execution()
-
-    def _table_iterator(self):
-        return self.original._table_iterator()
-
-    def _locate_oid_column(self):
-        if self.selectable.oid_column is not None:
-            return self.selectable.oid_column._make_proxy(self)
-        else:
-            return None
-
-    def named_with_column(self):
-        return True
-
-    def _exportable_columns(self):
-        #return self.selectable._exportable_columns()
-        return self.selectable.columns
-
-    def _copy_internals(self):
-        self._clone_from_clause()
-        self.selectable = self.selectable._clone()
-        baseselectable = self.selectable
-        while isinstance(baseselectable, Alias):
-            baseselectable = baseselectable.selectable
-        self.original = baseselectable
-
-    def get_children(self, **kwargs):
-        for c in self.c:
-            yield c
-        yield self.selectable
-
-    def _get_from_objects(self):
-        return [self]
-
-    bind = property(lambda s: s.selectable.bind)
-
-class _ColumnElementAdapter(ColumnElement):
-    """Adapts a ClauseElement which may or may not be a
-    ColumnElement subclass itself into an object which
-    acts like a ColumnElement.
-    """
-
-    def __init__(self, elem):
-        self.elem = elem
-        self.type = getattr(elem, 'type', None)
-        self.orig_set = getattr(elem, 'orig_set', util.Set())
-
-    key = property(lambda s: s.elem.key)
-    _label = property(lambda s: s.elem._label)
-
-    def _copy_internals(self):
-        self.elem = self.elem._clone()
-
-    def get_children(self, **kwargs):
-        return self.elem,
-
-    def _hide_froms(self, **modifiers):
-        return self.elem._hide_froms(**modifiers)
-
-    def _get_from_objects(self, **modifiers):
-        return self.elem._get_from_objects(**modifiers)
-
-    def __getattr__(self, attr):
-        return getattr(self.elem, attr)
-
-class _Grouping(_ColumnElementAdapter):
-    """Represent a grouping within a column expression"""
-    pass
-
-class _FromGrouping(FromClause):
-    """Represent a grouping of a FROM clause"""
-    __visit_name__ = 'grouping'
-
-    def __init__(self, elem):
-        self.elem = elem
-
-    columns = c = property(lambda s:s.elem.columns)
-
-    def get_children(self, **kwargs):
-        return self.elem,
-
-    def _hide_froms(self, **modifiers):
-        return self.elem._hide_froms(**modifiers)
-
-    def _copy_internals(self):
-        self.elem = self.elem._clone()
-
-    def _get_from_objects(self, **modifiers):
-        return self.elem._get_from_objects(**modifiers)
-
-    def __getattr__(self, attr):
-        return getattr(self.elem, attr)
-
-class _Label(ColumnElement):
-    """Represents a column label (AS).
-
-    Represent a label, as typically applied to any column-level
-    element using the ``AS`` sql keyword.
-
-    This object is constructed from the ``label()`` module level
-    function as well as the ``label()`` method available on all
-    ``ColumnElement`` subclasses.
-    """
-
-    def __init__(self, name, obj, type_=None):
-        while isinstance(obj, _Label):
-            obj = obj.obj
-        self.name = name or "{ANON %d %s}" % (id(self), getattr(obj, 'name', 'anon'))
-
-        self.obj = obj.self_group(against=operators.as_)
-        self.type = sqltypes.to_instance(type_ or getattr(obj, 'type', None))
-
-    key = property(lambda s: s.name)
-    _label = property(lambda s: s.name)
-    orig_set = property(lambda s:s.obj.orig_set)
-
-    def expression_element(self):
-        return self.obj
-
-    def _copy_internals(self):
-        self.obj = self.obj._clone()
-
-    def get_children(self, **kwargs):
-        return self.obj,
-
-    def _get_from_objects(self, **modifiers):
-        return self.obj._get_from_objects(**modifiers)
-
-    def _hide_froms(self, **modifiers):
-        return self.obj._hide_froms(**modifiers)
-
-    def _make_proxy(self, selectable, name = None):
-        if isinstance(self.obj, (Selectable, ColumnElement)):
-            return self.obj._make_proxy(selectable, name=self.name)
-        else:
-            return column(self.name)._make_proxy(selectable=selectable)
-
-class _ColumnClause(ColumnElement):
-    """Represents a generic column expression from any textual string.
-
-    This includes columns associated with tables, aliases and select
-    statements, but also any arbitrary text.  May or may not be bound
-    to an underlying ``Selectable``.  ``_ColumnClause`` is usually
-    created publically via the ``column()`` function or the
-    ``literal_column()`` function.
-
-    text
-      the text of the element.
-
-    selectable
-      parent selectable.
-
-    type
-      ``TypeEngine`` object which can associate this ``_ColumnClause``
-      with a type.
-
-    is_literal
-      if True, the ``_ColumnClause`` is assumed to be an exact
-      expression that will be delivered to the output with no quoting
-      rules applied regardless of case sensitive settings.  the
-      ``literal_column()`` function is usually used to create such a
-      ``_ColumnClause``.
-    """
-
-    def __init__(self, text, selectable=None, type_=None, _is_oid=False, is_literal=False):
-        self.key = self.name = text
-        self.encodedname = isinstance(self.name, unicode) and self.name.encode('ascii', 'backslashreplace') or self.name
-        self.table = selectable
-        self.type = sqltypes.to_instance(type_)
-        self._is_oid = _is_oid
-        self._distance = 0
-        self.__label = None
-        self.is_literal = is_literal
-
-    def _clone(self):
-        # ColumnClause is immutable
-        return self
-
-    def _get_label(self):
-        """Generate a 'label' for this column.
-
-        The label is a product of the parent table name and column
-        name, and is treated as a unique identifier of this ``Column``
-        across all ``Tables`` and derived selectables for a particular
-        metadata collection.
-        """
-
-        # for a "literal" column, we've no idea what the text is
-        # therefore no 'label' can be automatically generated
-        if self.is_literal:
-            return None
-        if self.__label is None:
-            if self.table is not None and self.table.named_with_column():
-                self.__label = self.table.name + "_" + self.name
-                counter = 1
-                while self.__label in self.table.c:
-                    self.__label = self.__label + "_%d" % counter
-                    counter += 1
-            else:
-                self.__label = self.name
-        return self.__label
-
-    is_labeled = property(lambda self:self.name != list(self.orig_set)[0].name)
-
-    _label = property(_get_label)
-
-    def label(self, name):
-        # if going off the "__label" property and its None, we have
-        # no label; return self
-        if name is None:
-            return self
-        else:
-            return super(_ColumnClause, self).label(name)
-
-    def _get_from_objects(self, **modifiers):
-        if self.table is not None:
-            return [self.table]
-        else:
-            return []
-
-    def _bind_param(self, obj):
-        return _BindParamClause(self._label, obj, shortname=self.name, type_=self.type, unique=True)
-
-    def _make_proxy(self, selectable, name = None):
-        # propigate the "is_literal" flag only if we are keeping our name,
-        # otherwise its considered to be a label
-        is_literal = self.is_literal and (name is None or name == self.name)
-        c = _ColumnClause(name or self.name, selectable=selectable, _is_oid=self._is_oid, type_=self.type, is_literal=is_literal)
-        c.orig_set = self.orig_set
-        c._distance = self._distance + 1
-        if not self._is_oid:
-            selectable.columns[c.name] = c
-        return c
-
-    def _compare_type(self, obj):
-        return self.type
-
-class TableClause(FromClause):
-    """Represents a "table" construct.
-
-    Note that this represents tables only as another syntactical
-    construct within SQL expressions; it does not provide schema-level
-    functionality.
-    """
-
-    def __init__(self, name, *columns):
-        super(TableClause, self).__init__(name)
-        self.name = self.fullname = name
-        self.encodedname = self.name.encode('ascii', 'backslashreplace')
-        self._oid_column = _ColumnClause('oid', self, _is_oid=True)
-        self._export_columns(columns)
-
-    def _clone(self):
-        # TableClause is immutable
-        return self
-
-    def named_with_column(self):
-        return True
-
-    def append_column(self, c):
-        self._columns[c.name] = c
-        c.table = self
-
-    def _locate_oid_column(self):
-        return self._oid_column
-
-    def _proxy_column(self, c):
-        self.append_column(c)
-        return c
-
-    def _orig_columns(self):
-        try:
-            return self._orig_cols
-        except AttributeError:
-            self._orig_cols= {}
-            for c in self.columns:
-                for ci in c.orig_set:
-                    self._orig_cols[ci] = c
-            return self._orig_cols
-
-    original_columns = property(_orig_columns)
-
-    def get_children(self, column_collections=True, **kwargs):
-        if column_collections:
-            return [c for c in self.c]
-        else:
-            return []
-
-    def _exportable_columns(self):
-        raise NotImplementedError()
-
-    def count(self, whereclause=None, **params):
-        if self.primary_key:
-            col = list(self.primary_key)[0]
-        else:
-            col = list(self.columns)[0]
-        return select([func.count(col).label('tbl_row_count')], whereclause, from_obj=[self], **params)
-
-    def join(self, right, *args, **kwargs):
-        return Join(self, right, *args, **kwargs)
-
-    def outerjoin(self, right, *args, **kwargs):
-        return Join(self, right, isouter = True, *args, **kwargs)
-
-    def alias(self, name=None):
-        return Alias(self, name)
-
-    def select(self, whereclause = None, **params):
-        return select([self], whereclause, **params)
-
-    def insert(self, values = None):
-        return insert(self, values=values)
-
-    def update(self, whereclause = None, values = None):
-        return update(self, whereclause, values)
-
-    def delete(self, whereclause = None):
-        return delete(self, whereclause)
-
-    def _get_from_objects(self, **modifiers):
-        return [self]
-
-
-class _SelectBaseMixin(object):
-    """Base class for ``Select`` and ``CompoundSelects``."""
-
-    def __init__(self, use_labels=False, for_update=False, limit=None, offset=None, order_by=None, group_by=None, bind=None):
-        self.use_labels = use_labels
-        self.for_update = for_update
-        self._limit = limit
-        self._offset = offset
-        self._bind = bind
-
-        self.append_order_by(*util.to_list(order_by, []))
-        self.append_group_by(*util.to_list(group_by, []))
-
-    def as_scalar(self):
-        return _ScalarSelect(self)
-
-    def apply_labels(self):
-        s = self._generate()
-        s.use_labels = True
-        return s
-
-    def label(self, name):
-        return self.as_scalar().label(name)
-
-    def supports_execution(self):
-        return True
-
-    def _generate(self):
-        s = self._clone()
-        s._clone_from_clause()
-        return s
-
-    def limit(self, limit):
-        s = self._generate()
-        s._limit = limit
-        return s
-
-    def offset(self, offset):
-        s = self._generate()
-        s._offset = offset
-        return s
-
-    def order_by(self, *clauses):
-        s = self._generate()
-        s.append_order_by(*clauses)
-        return s
-
-    def group_by(self, *clauses):
-        s = self._generate()
-        s.append_group_by(*clauses)
-        return s
-
-    def append_order_by(self, *clauses):
-        if clauses == [None]:
-            self._order_by_clause = ClauseList()
-        else:
-            if getattr(self, '_order_by_clause', None):
-                clauses = list(self._order_by_clause) + list(clauses)
-            self._order_by_clause = ClauseList(*clauses)
-
-    def append_group_by(self, *clauses):
-        if clauses == [None]:
-            self._group_by_clause = ClauseList()
-        else:
-            if getattr(self, '_group_by_clause', None):
-                clauses = list(self._group_by_clause) + list(clauses)
-            self._group_by_clause = ClauseList(*clauses)
-
-    def select(self, whereclauses = None, **params):
-        return select([self], whereclauses, **params)
-
-    def _get_from_objects(self, is_where=False, **modifiers):
-        if is_where:
-            return []
-        else:
-            return [self]
-
-class _ScalarSelect(_Grouping):
-    __visit_name__ = 'grouping'
-
-    def __init__(self, elem):
-        super(_ScalarSelect, self).__init__(elem)
-        self.type = list(elem.inner_columns)[0].type
-
-    def _no_cols(self):
-        raise exceptions.InvalidRequestError("Scalar Select expression has no columns; use this object directly within a column-level expression.")
-    c = property(_no_cols)
-    columns = c
-
-    def self_group(self, **kwargs):
-        return self
-
-    def _make_proxy(self, selectable, name):
-        return list(self.inner_columns)[0]._make_proxy(selectable, name)
-
-    def _get_from_objects(self, **modifiers):
-        return []
-
-class CompoundSelect(_SelectBaseMixin, FromClause):
-    def __init__(self, keyword, *selects, **kwargs):
-        self._should_correlate = kwargs.pop('correlate', False)
-        self.keyword = keyword
-        self.selects = []
-
-        # some DBs do not like ORDER BY in the inner queries of a UNION, etc.
-        for n, s in enumerate(selects):
-            if s._order_by_clause:
-                s = s.order_by(None)
-            # unions group from left to right, so don't group first select
-            if n:
-                self.selects.append(s.self_group(self))
-            else:
-                self.selects.append(s)
-
-        self._col_map = {}
-
-        _SelectBaseMixin.__init__(self, **kwargs)
-
-    name = property(lambda s:s.keyword + " statement")
-
-    def self_group(self, against=None):
-        return _FromGrouping(self)
-
-    def _locate_oid_column(self):
-        return self.selects[0].oid_column
-
-    def _exportable_columns(self):
-        for s in self.selects:
-            for c in s.c:
-                yield c
-
-    def _proxy_column(self, column):
-        if self.use_labels:
-            col = column._make_proxy(self, name=column._label)
-        else:
-            col = column._make_proxy(self)
-        try:
-            colset = self._col_map[col.name]
-        except KeyError:
-            colset = util.Set()
-            self._col_map[col.name] = colset
-        [colset.add(c) for c in col.orig_set]
-        col.orig_set = colset
-        return col
-
-    def _copy_internals(self):
-        self._clone_from_clause()
-        self._col_map = {}
-        self.selects = [s._clone() for s in self.selects]
-        for attr in ('_order_by_clause', '_group_by_clause'):
-            if getattr(self, attr) is not None:
-                setattr(self, attr, getattr(self, attr)._clone())
-
-    def get_children(self, column_collections=True, **kwargs):
-        return (column_collections and list(self.c) or []) + \
-            [self._order_by_clause, self._group_by_clause] + list(self.selects)
-
-    def _table_iterator(self):
-        for s in self.selects:
-            for t in s._table_iterator():
-                yield t
-
-    def _find_engine(self):
-        for s in self.selects:
-            e = s._find_engine()
-            if e:
-                return e
-        else:
-            return None
-
-class Select(_SelectBaseMixin, FromClause):
-    """Represents a ``SELECT`` statement.
-
-    Select statements support appendable clauses, as well as the
-    ability to execute themselves and return a result set.
-    """
-
-    def __init__(self, columns, whereclause=None, from_obj=None, distinct=False, having=None, correlate=True, prefixes=None, **kwargs):
-        """Construct a Select object.
-
-        The public constructor for Select is the
-        [sqlalchemy.sql#select()] function; see that function for
-        argument descriptions.
-        """
-
-        self._should_correlate = correlate
-        self._distinct = distinct
-
-        self._raw_columns = []
-        self.__correlate = util.Set()
-        self._froms = util.OrderedSet()
-        self._whereclause = None
-        self._having = None
-        self._prefixes = []
-
-        if columns is not None:
-            for c in columns:
-                self.append_column(c)
-
-        if from_obj is not None:
-            for f in from_obj:
-                self.append_from(f)
-
-        if whereclause is not None:
-            self.append_whereclause(whereclause)
-
-        if having is not None:
-            self.append_having(having)
-
-        if prefixes is not None:
-            for p in prefixes:
-                self.append_prefix(p)
-
-        _SelectBaseMixin.__init__(self, **kwargs)
-
-    def _get_display_froms(self, existing_froms=None):
-        """Return the full list of 'from' clauses to be displayed.
-
-        Takes into account a set of existing froms which may be
-        rendered in the FROM clause of enclosing selects; this Select
-        may want to leave those absent if it is automatically
-        correlating.
-        """
-
-        froms = util.OrderedSet()
-        hide_froms = util.Set()
-
-        for col in self._raw_columns:
-            for f in col._hide_froms():
-                hide_froms.add(f)
-            for f in col._get_from_objects():
-                froms.add(f)
-
-        if self._whereclause is not None:
-            for f in self._whereclause._get_from_objects(is_where=True):
-                froms.add(f)
-
-        for elem in self._froms:
-            froms.add(elem)
-            for f in elem._get_from_objects():
-                froms.add(f)
-
-        for elem in froms:
-            for f in elem._hide_froms():
-                hide_froms.add(f)
-
-        froms = froms.difference(hide_froms)
-
-        if len(froms) > 1:
-            corr = self.__correlate
-            if self._should_correlate and existing_froms is not None:
-                corr = existing_froms.union(corr)
-            f = froms.difference(corr)
-            if len(f) == 0:
-                raise exceptions.InvalidRequestError("Select statement '%s' is overcorrelated; returned no 'from' clauses" % str(self.__dont_correlate()))
-            return f
-        else:
-            return froms
-
-    froms = property(_get_display_froms, doc="""Return a list of all FromClause elements which will be applied to the FROM clause of the resulting statement.""")
-
-    name = property(lambda self:"Select statement")
-
-    def locate_all_froms(self):
-        froms = util.Set()
-        for col in self._raw_columns:
-            for f in col._get_from_objects():
-                froms.add(f)
-
-        if self._whereclause is not None:
-            for f in self._whereclause._get_from_objects(is_where=True):
-                froms.add(f)
-
-        for elem in self._froms:
-            froms.add(elem)
-            for f in elem._get_from_objects():
-                froms.add(f)
-        return froms
-
-    def _get_inner_columns(self):
-        for c in self._raw_columns:
-            if isinstance(c, Selectable):
-                for co in c.columns:
-                    yield co
-            else:
-                yield c
-
-    inner_columns = property(_get_inner_columns)
-
-    def _copy_internals(self):
-        self._clone_from_clause()
-        self._raw_columns = [c._clone() for c in self._raw_columns]
-        self._recorrelate_froms([(f, f._clone()) for f in self._froms])
-        for attr in ('_whereclause', '_having', '_order_by_clause', '_group_by_clause'):
-            if getattr(self, attr) is not None:
-                setattr(self, attr, getattr(self, attr)._clone())
-
-    def get_children(self, column_collections=True, **kwargs):
-        return (column_collections and list(self.columns) or []) + \
-            list(self.locate_all_froms()) + \
-            [x for x in (self._whereclause, self._having, self._order_by_clause, self._group_by_clause) if x is not None]
-
-    def _recorrelate_froms(self, froms):
-        newcorrelate = util.Set()
-        newfroms = util.Set()
-        oldfroms = util.Set(self._froms)
-        for old, new in froms:
-            if old in self.__correlate:
-                newcorrelate.add(new)
-                self.__correlate.remove(old)
-            if old in oldfroms:
-                newfroms.add(new)
-                oldfroms.remove(old)
-        self.__correlate = self.__correlate.union(newcorrelate)
-        self._froms = [f for f in oldfroms.union(newfroms)]
-
-    def column(self, column):
-        s = self._generate()
-        s.append_column(column)
-        return s
-
-    def where(self, whereclause):
-        s = self._generate()
-        s.append_whereclause(whereclause)
-        return s
-
-    def having(self, having):
-        s = self._generate()
-        s.append_having(having)
-        return s
-
-    def distinct(self):
-        s = self._generate()
-        s._distinct = True
-        return s
-
-    def prefix_with(self, clause):
-        s = self._generate()
-        s.append_prefix(clause)
-        return s
-
-    def select_from(self, fromclause):
-        s = self._generate()
-        s.append_from(fromclause)
-        return s
-
-    def __dont_correlate(self):
-        s = self._generate()
-        s._should_correlate = False
-        return s
-
-    def correlate(self, fromclause):
-        s = self._generate()
-        s._should_correlate=False
-        if fromclause is None:
-            s.__correlate = util.Set()
-        else:
-            s.append_correlation(fromclause)
-        return s
-
-    def append_correlation(self, fromclause):
-        self.__correlate.add(fromclause)
-
-    def append_column(self, column):
-        column = _literal_as_column(column)
-
-        if isinstance(column, _ScalarSelect):
-            column = column.self_group(against=operators.comma_op)
-
-        self._raw_columns.append(column)
-
-    def append_prefix(self, clause):
-        clause = _literal_as_text(clause)
-        self._prefixes.append(clause)
-
-    def append_whereclause(self, whereclause):
-        if self._whereclause  is not None:
-            self._whereclause = and_(self._whereclause, _literal_as_text(whereclause))
-        else:
-            self._whereclause = _literal_as_text(whereclause)
-
-    def append_having(self, having):
-        if self._having is not None:
-            self._having = and_(self._having, _literal_as_text(having))
-        else:
-            self._having = _literal_as_text(having)
-
-    def append_from(self, fromclause):
-        if _is_literal(fromclause):
-            fromclause = FromClause(fromclause)
-        self._froms.add(fromclause)
-
-    def _exportable_columns(self):
-        return [c for c in self._raw_columns if isinstance(c, (Selectable, ColumnElement))]
-
-    def _proxy_column(self, column):
-        if self.use_labels:
-            return column._make_proxy(self, name=column._label)
-        else:
-            return column._make_proxy(self)
-
-    def self_group(self, against=None):
-        if isinstance(against, CompoundSelect):
-            return self
-        return _FromGrouping(self)
-
-    def _locate_oid_column(self):
-        for f in self.locate_all_froms():
-            if f is self:
-                # we might be in our own _froms list if a column with
-                # us as the parent is attached, which includes textual
-                # columns.
-                continue
-            oid = f.oid_column
-            if oid is not None:
-                return oid
-        else:
-            return None
-
-    def union(self, other, **kwargs):
-        return union(self, other, **kwargs)
-
-    def union_all(self, other, **kwargs):
-        return union_all(self, other, **kwargs)
-
-    def except_(self, other, **kwargs):
-        return except_(self, other, **kwargs)
-
-    def except_all(self, other, **kwargs):
-        return except_all(self, other, **kwargs)
-
-    def intersect(self, other, **kwargs):
-        return intersect(self, other, **kwargs)
-
-    def intersect_all(self, other, **kwargs):
-        return intersect_all(self, other, **kwargs)
-
-    def _table_iterator(self):
-        for t in NoColumnVisitor().iterate(self):
-            if isinstance(t, TableClause):
-                yield t
-
-    def _find_engine(self):
-        """Try to return a Engine, either explicitly set in this
-        object, or searched within the from clauses for one.
-        """
-
-        if self._bind is not None:
-            return self._bind
-        for f in self._froms:
-            if f is self:
-                continue
-            e = f.bind
-            if e is not None:
-                self._bind = e
-                return e
-        # look through the columns (largely synomous with looking
-        # through the FROMs except in the case of _CalculatedClause/_Function)
-        for c in self._exportable_columns():
-            if getattr(c, 'table', None) is self:
-                continue
-            e = c.bind
-            if e is not None:
-                self._bind = e
-                return e
-        return None
-
-class _UpdateBase(ClauseElement):
-    """Form the base for ``INSERT``, ``UPDATE``, and ``DELETE`` statements."""
-
-    def supports_execution(self):
-        return True
-
-    def _table_iterator(self):
-        return iter([self.table])
-
-    def _process_colparams(self, parameters):
-        """Receive the *values* of an ``INSERT`` or ``UPDATE`` statement and construct appropriate bind parameters."""
-
-        if parameters is None:
-            return None
-
-        if isinstance(parameters, (list, tuple)):
-            pp = {}
-            i = 0
-            for c in self.table.c:
-                pp[c.key] = parameters[i]
-                i +=1
-            parameters = pp
-
-        for key in parameters.keys():
-            value = parameters[key]
-            if isinstance(value, ClauseElement):
-                parameters[key] = value.self_group()
-            elif _is_literal(value):
-                if _is_literal(key):
-                    col = self.table.c[key]
-                else:
-                    col = key
-                try:
-                    parameters[key] = bindparam(col, value, unique=True)
-                except KeyError:
-                    del parameters[key]
-        return parameters
-
-    def _find_engine(self):
-        return self.table.bind
-
-class Insert(_UpdateBase):
-    def __init__(self, table, values=None):
-        self.table = table
-        self.select = None
-        self.parameters = self._process_colparams(values)
-
-    def get_children(self, **kwargs):
-        if self.select is not None:
-            return self.select,
-        else:
-            return ()
-
-    def _copy_internals(self):
-        self.parameters = self.parameters.copy()
-
-    def values(self, v):
-        if len(v) == 0:
-            return self
-        u = self._clone()
-        if u.parameters is None:
-            u.parameters = u._process_colparams(v)
-        else:
-            u.parameters = self.parameters.copy()
-            u.parameters.update(u._process_colparams(v))
-        return u
-
-class Update(_UpdateBase):
-    def __init__(self, table, whereclause, values=None):
-        self.table = table
-        self._whereclause = whereclause
-        self.parameters = self._process_colparams(values)
-
-    def get_children(self, **kwargs):
-        if self._whereclause is not None:
-            return self._whereclause,
-        else:
-            return ()
-
-    def _copy_internals(self):
-        self._whereclause = self._whereclause._clone()
-        self.parameters = self.parameters.copy()
-
-    def values(self, v):
-        if len(v) == 0:
-            return self
-        u = self._clone()
-        if u.parameters is None:
-            u.parameters = u._process_colparams(v)
-        else:
-            u.parameters = self.parameters.copy()
-            u.parameters.update(u._process_colparams(v))
-        return u
-
-class Delete(_UpdateBase):
-    def __init__(self, table, whereclause):
-        self.table = table
-        self._whereclause = whereclause
-
-    def get_children(self, **kwargs):
-        if self._whereclause is not None:
-            return self._whereclause,
-        else:
-            return ()
-
-    def _copy_internals(self):
-        self._whereclause = self._whereclause._clone()
-
-class _IdentifiedClause(ClauseElement):
-    def __init__(self, ident):
-        self.ident = ident
-    def supports_execution(self):
-        return True
-
-class SavepointClause(_IdentifiedClause):
-    pass
-
-class RollbackToSavepointClause(_IdentifiedClause):
-    pass
-
-class ReleaseSavepointClause(_IdentifiedClause):
-    pass