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# Copyright (C) 2009-2014 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""
Provide :class:`.Insert`, :class:`.Update` and :class:`.Delete`.
"""
from .base import Executable, _generative, _from_objects, DialectKWArgs
from .elements import ClauseElement, _literal_as_text, Null, and_, _clone
from .selectable import _interpret_as_from, _interpret_as_select, HasPrefixes
from .. import util
from .. import exc
class UpdateBase(DialectKWArgs, HasPrefixes, Executable, ClauseElement):
"""Form the base for ``INSERT``, ``UPDATE``, and ``DELETE`` statements.
"""
__visit_name__ = 'update_base'
_execution_options = \
Executable._execution_options.union({'autocommit': True})
_hints = util.immutabledict()
_prefixes = ()
def _process_colparams(self, parameters):
def process_single(p):
if isinstance(p, (list, tuple)):
return dict(
(c.key, pval)
for c, pval in zip(self.table.c, p)
)
else:
return p
if (isinstance(parameters, (list, tuple)) and parameters and
isinstance(parameters[0], (list, tuple, dict))):
if not self._supports_multi_parameters:
raise exc.InvalidRequestError(
"This construct does not support "
"multiple parameter sets.")
return [process_single(p) for p in parameters], True
else:
return process_single(parameters), False
def params(self, *arg, **kw):
"""Set the parameters for the statement.
This method raises ``NotImplementedError`` on the base class,
and is overridden by :class:`.ValuesBase` to provide the
SET/VALUES clause of UPDATE and INSERT.
"""
raise NotImplementedError(
"params() is not supported for INSERT/UPDATE/DELETE statements."
" To set the values for an INSERT or UPDATE statement, use"
" stmt.values(**parameters).")
def bind(self):
"""Return a 'bind' linked to this :class:`.UpdateBase`
or a :class:`.Table` associated with it.
"""
return self._bind or self.table.bind
def _set_bind(self, bind):
self._bind = bind
bind = property(bind, _set_bind)
@_generative
def returning(self, *cols):
"""Add a :term:`RETURNING` or equivalent clause to this statement.
e.g.::
stmt = table.update().\\
where(table.c.data == 'value').\\
values(status='X').\\
returning(table.c.server_flag,
table.c.updated_timestamp)
for server_flag, updated_timestamp in connection.execute(stmt):
print(server_flag, updated_timestamp)
The given collection of column expressions should be derived from
the table that is
the target of the INSERT, UPDATE, or DELETE. While :class:`.Column`
objects are typical, the elements can also be expressions::
stmt = table.insert().returning(
(table.c.first_name + " " + table.c.last_name).
label('fullname'))
Upon compilation, a RETURNING clause, or database equivalent,
will be rendered within the statement. For INSERT and UPDATE,
the values are the newly inserted/updated values. For DELETE,
the values are those of the rows which were deleted.
Upon execution, the values of the columns to be returned are made
available via the result set and can be iterated using
:meth:`.ResultProxy.fetchone` and similar. For DBAPIs which do not
natively support returning values (i.e. cx_oracle), SQLAlchemy will
approximate this behavior at the result level so that a reasonable
amount of behavioral neutrality is provided.
Note that not all databases/DBAPIs
support RETURNING. For those backends with no support,
an exception is raised upon compilation and/or execution.
For those who do support it, the functionality across backends
varies greatly, including restrictions on executemany()
and other statements which return multiple rows. Please
read the documentation notes for the database in use in
order to determine the availability of RETURNING.
.. seealso::
:meth:`.ValuesBase.return_defaults` - an alternative method tailored
towards efficient fetching of server-side defaults and triggers
for single-row INSERTs or UPDATEs.
"""
self._returning = cols
@_generative
def with_hint(self, text, selectable=None, dialect_name="*"):
"""Add a table hint for a single table to this
INSERT/UPDATE/DELETE statement.
.. note::
:meth:`.UpdateBase.with_hint` currently applies only to
Microsoft SQL Server. For MySQL INSERT/UPDATE/DELETE hints, use
:meth:`.UpdateBase.prefix_with`.
The text of the hint is rendered in the appropriate
location for the database backend in use, relative
to the :class:`.Table` that is the subject of this
statement, or optionally to that of the given
:class:`.Table` passed as the ``selectable`` argument.
The ``dialect_name`` option will limit the rendering of a particular
hint to a particular backend. Such as, to add a hint
that only takes effect for SQL Server::
mytable.insert().with_hint("WITH (PAGLOCK)", dialect_name="mssql")
.. versionadded:: 0.7.6
:param text: Text of the hint.
:param selectable: optional :class:`.Table` that specifies
an element of the FROM clause within an UPDATE or DELETE
to be the subject of the hint - applies only to certain backends.
:param dialect_name: defaults to ``*``, if specified as the name
of a particular dialect, will apply these hints only when
that dialect is in use.
"""
if selectable is None:
selectable = self.table
self._hints = self._hints.union(
{(selectable, dialect_name): text})
class ValuesBase(UpdateBase):
"""Supplies support for :meth:`.ValuesBase.values` to
INSERT and UPDATE constructs."""
__visit_name__ = 'values_base'
_supports_multi_parameters = False
_has_multi_parameters = False
select = None
def __init__(self, table, values, prefixes):
self.table = _interpret_as_from(table)
self.parameters, self._has_multi_parameters = \
self._process_colparams(values)
if prefixes:
self._setup_prefixes(prefixes)
@_generative
def values(self, *args, **kwargs):
"""specify a fixed VALUES clause for an INSERT statement, or the SET
clause for an UPDATE.
Note that the :class:`.Insert` and :class:`.Update` constructs support
per-execution time formatting of the VALUES and/or SET clauses,
based on the arguments passed to :meth:`.Connection.execute`.
However, the :meth:`.ValuesBase.values` method can be used to "fix" a
particular set of parameters into the statement.
Multiple calls to :meth:`.ValuesBase.values` will produce a new
construct, each one with the parameter list modified to include
the new parameters sent. In the typical case of a single
dictionary of parameters, the newly passed keys will replace
the same keys in the previous construct. In the case of a list-based
"multiple values" construct, each new list of values is extended
onto the existing list of values.
:param \**kwargs: key value pairs representing the string key
of a :class:`.Column` mapped to the value to be rendered into the
VALUES or SET clause::
users.insert().values(name="some name")
users.update().where(users.c.id==5).values(name="some name")
:param \*args: Alternatively, a dictionary, tuple or list
of dictionaries or tuples can be passed as a single positional
argument in order to form the VALUES or
SET clause of the statement. The single dictionary form
works the same as the kwargs form::
users.insert().values({"name": "some name"})
If a tuple is passed, the tuple should contain the same number
of columns as the target :class:`.Table`::
users.insert().values((5, "some name"))
The :class:`.Insert` construct also supports multiply-rendered VALUES
construct, for those backends which support this SQL syntax
(SQLite, Postgresql, MySQL). This mode is indicated by passing a
list of one or more dictionaries/tuples::
users.insert().values([
{"name": "some name"},
{"name": "some other name"},
{"name": "yet another name"},
])
In the case of an :class:`.Update`
construct, only the single dictionary/tuple form is accepted,
else an exception is raised. It is also an exception case to
attempt to mix the single-/multiple- value styles together,
either through multiple :meth:`.ValuesBase.values` calls
or by sending a list + kwargs at the same time.
.. note::
Passing a multiple values list is *not* the same
as passing a multiple values list to the
:meth:`.Connection.execute` method. Passing a list of parameter
sets to :meth:`.ValuesBase.values` produces a construct of this
form::
INSERT INTO table (col1, col2, col3) VALUES
(col1_0, col2_0, col3_0),
(col1_1, col2_1, col3_1),
...
whereas a multiple list passed to :meth:`.Connection.execute`
has the effect of using the DBAPI
`executemany() <http://www.python.org/dev/peps/pep-0249/#id18>`_
method, which provides a high-performance system of invoking
a single-row INSERT statement many times against a series
of parameter sets. The "executemany" style is supported by
all database backends, as it does not depend on a special SQL
syntax.
.. versionadded:: 0.8
Support for multiple-VALUES INSERT statements.
.. seealso::
:ref:`inserts_and_updates` - SQL Expression
Language Tutorial
:func:`~.expression.insert` - produce an ``INSERT`` statement
:func:`~.expression.update` - produce an ``UPDATE`` statement
"""
if self.select is not None:
raise exc.InvalidRequestError(
"This construct already inserts from a SELECT")
if self._has_multi_parameters and kwargs:
raise exc.InvalidRequestError(
"This construct already has multiple parameter sets.")
if args:
if len(args) > 1:
raise exc.ArgumentError(
"Only a single dictionary/tuple or list of "
"dictionaries/tuples is accepted positionally.")
v = args[0]
else:
v = {}
if self.parameters is None:
self.parameters, self._has_multi_parameters = \
self._process_colparams(v)
else:
if self._has_multi_parameters:
self.parameters = list(self.parameters)
p, self._has_multi_parameters = self._process_colparams(v)
if not self._has_multi_parameters:
raise exc.ArgumentError(
"Can't mix single-values and multiple values "
"formats in one statement")
self.parameters.extend(p)
else:
self.parameters = self.parameters.copy()
p, self._has_multi_parameters = self._process_colparams(v)
if self._has_multi_parameters:
raise exc.ArgumentError(
"Can't mix single-values and multiple values "
"formats in one statement")
self.parameters.update(p)
if kwargs:
if self._has_multi_parameters:
raise exc.ArgumentError(
"Can't pass kwargs and multiple parameter sets "
"simultaenously")
else:
self.parameters.update(kwargs)
@_generative
def return_defaults(self, *cols):
"""Make use of a :term:`RETURNING` clause for the purpose
of fetching server-side expressions and defaults.
E.g.::
stmt = table.insert().values(data='newdata').return_defaults()
result = connection.execute(stmt)
server_created_at = result.returned_defaults['created_at']
When used against a backend that supports RETURNING, all column
values generated by SQL expression or server-side-default will be
added to any existing RETURNING clause, provided that
:meth:`.UpdateBase.returning` is not used simultaneously. The column
values will then be available on the result using the
:attr:`.ResultProxy.returned_defaults` accessor as a dictionary,
referring to values keyed to the :class:`.Column` object as well as
its ``.key``.
This method differs from :meth:`.UpdateBase.returning` in these ways:
1. :meth:`.ValuesBase.return_defaults` is only intended for use with
an INSERT or an UPDATE statement that matches exactly one row.
While the RETURNING construct in the general sense supports
multiple rows for a multi-row UPDATE or DELETE statement, or for
special cases of INSERT that return multiple rows (e.g. INSERT from
SELECT, multi-valued VALUES clause),
:meth:`.ValuesBase.return_defaults` is intended only for an
"ORM-style" single-row INSERT/UPDATE statement. The row returned
by the statement is also consumed implcitly when
:meth:`.ValuesBase.return_defaults` is used. By contrast,
:meth:`.UpdateBase.returning` leaves the RETURNING result-set
intact with a collection of any number of rows.
2. It is compatible with the existing logic to fetch auto-generated
primary key values, also known as "implicit returning". Backends
that support RETURNING will automatically make use of RETURNING in
order to fetch the value of newly generated primary keys; while the
:meth:`.UpdateBase.returning` method circumvents this behavior,
:meth:`.ValuesBase.return_defaults` leaves it intact.
3. It can be called against any backend. Backends that don't support
RETURNING will skip the usage of the feature, rather than raising
an exception. The return value of
:attr:`.ResultProxy.returned_defaults` will be ``None``
:meth:`.ValuesBase.return_defaults` is used by the ORM to provide
an efficient implementation for the ``eager_defaults`` feature of
:func:`.mapper`.
:param cols: optional list of column key names or :class:`.Column`
objects. If omitted, all column expressions evaulated on the server
are added to the returning list.
.. versionadded:: 0.9.0
.. seealso::
:meth:`.UpdateBase.returning`
:attr:`.ResultProxy.returned_defaults`
"""
self._return_defaults = cols or True
class Insert(ValuesBase):
"""Represent an INSERT construct.
The :class:`.Insert` object is created using the
:func:`~.expression.insert()` function.
.. seealso::
:ref:`coretutorial_insert_expressions`
"""
__visit_name__ = 'insert'
_supports_multi_parameters = True
def __init__(self,
table,
values=None,
inline=False,
bind=None,
prefixes=None,
returning=None,
return_defaults=False,
**dialect_kw):
"""Construct an :class:`.Insert` object.
Similar functionality is available via the
:meth:`~.TableClause.insert` method on
:class:`~.schema.Table`.
:param table: :class:`.TableClause` which is the subject of the
insert.
:param values: collection of values to be inserted; see
:meth:`.Insert.values` for a description of allowed formats here.
Can be omitted entirely; a :class:`.Insert` construct will also
dynamically render the VALUES clause at execution time based on
the parameters passed to :meth:`.Connection.execute`.
:param inline: if True, SQL defaults will be compiled 'inline' into
the statement and not pre-executed.
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
:class:`~sqlalchemy.schema.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.
.. seealso::
:ref:`coretutorial_insert_expressions` - SQL Expression Tutorial
:ref:`inserts_and_updates` - SQL Expression Tutorial
"""
ValuesBase.__init__(self, table, values, prefixes)
self._bind = bind
self.select = self.select_names = None
self.inline = inline
self._returning = returning
self._validate_dialect_kwargs(dialect_kw)
self._return_defaults = return_defaults
def get_children(self, **kwargs):
if self.select is not None:
return self.select,
else:
return ()
@_generative
def from_select(self, names, select):
"""Return a new :class:`.Insert` construct which represents
an ``INSERT...FROM SELECT`` statement.
e.g.::
sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5)
ins = table2.insert().from_select(['a', 'b'], sel)
:param names: a sequence of string column names or :class:`.Column`
objects representing the target columns.
:param select: a :func:`.select` construct, :class:`.FromClause`
or other construct which resolves into a :class:`.FromClause`,
such as an ORM :class:`.Query` object, etc. The order of
columns returned from this FROM clause should correspond to the
order of columns sent as the ``names`` parameter; while this
is not checked before passing along to the database, the database
would normally raise an exception if these column lists don't
correspond.
.. warning::
The ``inline=True`` flag should be set to True when using
backends that support RETURNING, including Postgresql, Oracle,
and SQL Server. This will prevent the implicit ``RETURNING``
clause from being appended to the statement, which is normally
used to fetch the "last inserted primary key" value. This feature
will raise an error if the statement inserts zero rows, and
on some backends (e.g. Oracle) it will raise an error if the
statement inserts more than one row.
:paramref:`.insert.inline` is set to True as follows::
sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5)
ins = table2.insert(inline=True).from_select(['a', 'b'], sel)
Version 1.0 of SQLAlchemy will set this flag to True in **all**
cases.
.. note::
Python-side and SQL function defaults, as described at
:ref:`metadata_defaults_toplevel`, are **not** automatically
included in the SELECT statement as rendered unless explicitly
added to the statement. The behavior of automatically rendering
these default values and expressions is available as of SQLAlchemy
version 1.0.0.
.. versionadded:: 0.8.3
"""
if self.parameters:
raise exc.InvalidRequestError(
"This construct already inserts value expressions")
self.parameters, self._has_multi_parameters = \
self._process_colparams(dict((n, Null()) for n in names))
self.select_names = names
self.select = _interpret_as_select(select)
def _copy_internals(self, clone=_clone, **kw):
# TODO: coverage
self.parameters = self.parameters.copy()
if self.select is not None:
self.select = _clone(self.select)
class Update(ValuesBase):
"""Represent an Update construct.
The :class:`.Update` object is created using the :func:`update()`
function.
"""
__visit_name__ = 'update'
def __init__(self,
table,
whereclause=None,
values=None,
inline=False,
bind=None,
prefixes=None,
returning=None,
return_defaults=False,
**dialect_kw):
"""Construct an :class:`.Update` object.
E.g.::
from sqlalchemy import update
stmt = update(users).where(users.c.id==5).\\
values(name='user #5')
Similar functionality is available via the
:meth:`~.TableClause.update` method on
:class:`.Table`::
stmt = users.update().\\
where(users.c.id==5).\\
values(name='user #5')
:param table: A :class:`.Table` object representing the database
table to be updated.
:param whereclause: Optional SQL expression describing the ``WHERE``
condition of the ``UPDATE`` statement. Modern applications
may prefer to use the generative :meth:`~Update.where()`
method to specify the ``WHERE`` clause.
The WHERE clause can refer to multiple tables.
For databases which support this, an ``UPDATE FROM`` clause will
be generated, or on MySQL, a multi-table update. The statement
will fail on databases that don't have support for multi-table
update statements. A SQL-standard method of referring to
additional tables in the WHERE clause is to use a correlated
subquery::
users.update().values(name='ed').where(
users.c.name==select([addresses.c.email_address]).\\
where(addresses.c.user_id==users.c.id).\\
as_scalar()
)
.. versionchanged:: 0.7.4
The WHERE clause can refer to multiple tables.
:param values:
Optional dictionary which specifies the ``SET`` conditions of the
``UPDATE``. If left as ``None``, the ``SET``
conditions are determined from those parameters passed to the
statement during the execution and/or compilation of the
statement. When compiled standalone without any parameters,
the ``SET`` clause generates for all columns.
Modern applications may prefer to use the generative
:meth:`.Update.values` method to set the values of the
UPDATE statement.
:param inline: if True, no attempt will be made to retrieve the
SQL-generated default values to be provided within the statement;
in particular,
this allows SQL expressions to be rendered 'inline' within the
statement without the need to pre-execute them beforehand; for
backends that support "returning", this turns off the "implicit
returning" feature for the statement.
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 :class:`.Column`
objects or their string identifiers (specifically the "key" of the
:class:`.Column`, normally but not necessarily equivalent to
its "name"). Normally, the
:class:`.Column` objects used here are expected to be
part of the target :class:`.Table` that is the table
to be updated. However when using MySQL, a multiple-table
UPDATE statement can refer to columns from any of
the tables referred to in the WHERE clause.
The values referred to in ``values`` are typically:
* a literal data value (i.e. string, number, etc.)
* a SQL expression, such as a related :class:`.Column`,
a scalar-returning :func:`.select` construct,
etc.
When combining :func:`.select` constructs within the values
clause of an :func:`.update` construct,
the subquery represented by the :func:`.select` should be
*correlated* to the parent table, that is, providing criterion
which links the table inside the subquery to the outer table
being updated::
users.update().values(
name=select([addresses.c.email_address]).\\
where(addresses.c.user_id==users.c.id).\\
as_scalar()
)
.. seealso::
:ref:`inserts_and_updates` - SQL Expression
Language Tutorial
"""
ValuesBase.__init__(self, table, values, prefixes)
self._bind = bind
self._returning = returning
if whereclause is not None:
self._whereclause = _literal_as_text(whereclause)
else:
self._whereclause = None
self.inline = inline
self._validate_dialect_kwargs(dialect_kw)
self._return_defaults = return_defaults
def get_children(self, **kwargs):
if self._whereclause is not None:
return self._whereclause,
else:
return ()
def _copy_internals(self, clone=_clone, **kw):
# TODO: coverage
self._whereclause = clone(self._whereclause, **kw)
self.parameters = self.parameters.copy()
@_generative
def where(self, whereclause):
"""return a new update() construct with the given expression added to
its WHERE clause, joined to the existing clause via AND, if any.
"""
if self._whereclause is not None:
self._whereclause = and_(self._whereclause,
_literal_as_text(whereclause))
else:
self._whereclause = _literal_as_text(whereclause)
@property
def _extra_froms(self):
# TODO: this could be made memoized
# if the memoization is reset on each generative call.
froms = []
seen = set([self.table])
if self._whereclause is not None:
for item in _from_objects(self._whereclause):
if not seen.intersection(item._cloned_set):
froms.append(item)
seen.update(item._cloned_set)
return froms
class Delete(UpdateBase):
"""Represent a DELETE construct.
The :class:`.Delete` object is created using the :func:`delete()`
function.
"""
__visit_name__ = 'delete'
def __init__(self,
table,
whereclause=None,
bind=None,
returning=None,
prefixes=None,
**dialect_kw):
"""Construct :class:`.Delete` object.
Similar functionality is available via the
:meth:`~.TableClause.delete` method on
:class:`~.schema.Table`.
:param table: The table to delete rows from.
:param whereclause: A :class:`.ClauseElement` describing the ``WHERE``
condition of the ``DELETE`` statement. Note that the
:meth:`~Delete.where()` generative method may be used instead.
.. seealso::
:ref:`deletes` - SQL Expression Tutorial
"""
self._bind = bind
self.table = _interpret_as_from(table)
self._returning = returning
if prefixes:
self._setup_prefixes(prefixes)
if whereclause is not None:
self._whereclause = _literal_as_text(whereclause)
else:
self._whereclause = None
self._validate_dialect_kwargs(dialect_kw)
def get_children(self, **kwargs):
if self._whereclause is not None:
return self._whereclause,
else:
return ()
@_generative
def where(self, whereclause):
"""Add the given WHERE clause to a newly returned delete construct."""
if self._whereclause is not None:
self._whereclause = and_(self._whereclause,
_literal_as_text(whereclause))
else:
self._whereclause = _literal_as_text(whereclause)
def _copy_internals(self, clone=_clone, **kw):
# TODO: coverage
self._whereclause = clone(self._whereclause, **kw)
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