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