Edit File: dml.py
# sql/dml.py # Copyright (C) 2009-2021 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:`_expression.Insert`, :class:`_expression.Update` and :class:`_expression.Delete`. """ from . import util as sql_util from .base import _from_objects from .base import _generative from .base import DialectKWArgs from .base import Executable from .elements import _clone from .elements import _column_as_key from .elements import _literal_as_text from .elements import and_ from .elements import ClauseElement from .elements import Null from .selectable import _interpret_as_from from .selectable import _interpret_as_select from .selectable import HasCTE from .selectable import HasPrefixes from .. import exc from .. import util class UpdateBase( HasCTE, 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() _parameter_ordering = None _prefixes = () named_with_column = False _return_defaults = None 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 self._preserve_parameter_order and parameters is not None: if not isinstance(parameters, list) or ( parameters and not isinstance(parameters[0], tuple) ): raise ValueError( "When preserve_parameter_order is True, " "values() only accepts a list of 2-tuples" ) self._parameter_ordering = [key for key, value in parameters] return dict(parameters), False 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:`_schema.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): r"""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:`_schema.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:`_engine.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. """ if self._return_defaults: raise exc.InvalidRequestError( "return_defaults() is already configured on this statement" ) if self._returning: util.warn( "The returning() method does not currently support multiple " "additive calls. The existing RETURNING clause being " "replaced by new columns." ) 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:`_schema.Table` that is the subject of this statement, or optionally to that of the given :class:`_schema.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") :param text: Text of the hint. :param selectable: optional :class:`_schema.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 _preserve_parameter_order = False select = None _post_values_clause = 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): r"""Specify a fixed VALUES clause for an INSERT statement, or the SET clause for an UPDATE. Note that the :class:`_expression.Insert` and :class:`_expression.Update` constructs support per-execution time formatting of the VALUES and/or SET clauses, based on the arguments passed to :meth:`_engine.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:`_schema.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: As an alternative to passing key/value parameters, 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 forms that are accepted vary based on whether this is an :class:`_expression.Insert` or an :class:`_expression.Update` construct. For either an :class:`_expression.Insert` or :class:`_expression.Update` construct, a single dictionary can be passed, which works the same as that of the kwargs form:: users.insert().values({"name": "some name"}) users.update().values({"name": "some new name"}) Also for either form but more typically for the :class:`_expression.Insert` construct, a tuple that contains an entry for every column in the table is also accepted:: users.insert().values((5, "some name")) The :class:`_expression.Insert` construct also supports being passed a list of dictionaries or full-table-tuples, which on the server will render the less common SQL syntax of "multiple values" - this syntax is supported on backends such as SQLite, PostgreSQL, MySQL, but not necessarily others:: users.insert().values([ {"name": "some name"}, {"name": "some other name"}, {"name": "yet another name"}, ]) The above form would render a multiple VALUES statement similar to:: INSERT INTO users (name) VALUES (:name_1), (:name_2), (:name_3) It is essential to note that **passing multiple values is NOT the same as using traditional executemany() form**. The above syntax is a **special** syntax not typically used. To emit an INSERT statement against multiple rows, the normal method is to pass a multiple values list to the :meth:`_engine.Connection.execute` method, which is supported by all database backends and is generally more efficient for a very large number of parameters. .. seealso:: :ref:`execute_multiple` - an introduction to the traditional Core method of multiple parameter set invocation for INSERTs and other statements. .. versionchanged:: 1.0.0 an INSERT that uses a multiple-VALUES clause, even a list of length one, implies that the :paramref:`_expression.Insert.inline` flag is set to True, indicating that the statement will not attempt to fetch the "last inserted primary key" or other defaults. The statement deals with an arbitrary number of rows, so the :attr:`_engine.ResultProxy.inserted_primary_key` accessor does not apply. .. versionchanged:: 1.0.0 A multiple-VALUES INSERT now supports columns with Python side default values and callables in the same way as that of an "executemany" style of invocation; the callable is invoked for each row. See :ref:`bug_3288` for other details. The :class:`_expression.Update` construct supports a special form which is a list of 2-tuples, which when provided must be passed in conjunction with the :paramref:`_expression.update.preserve_parameter_order` parameter. This form causes the UPDATE statement to render the SET clauses using the order of parameters given to :meth:`_expression.Update.values`, rather than the ordering of columns given in the :class:`_schema.Table`. .. versionadded:: 1.0.10 - added support for parameter-ordered UPDATE statements via the :paramref:`_expression.update.preserve_parameter_order` flag. .. seealso:: :ref:`updates_order_parameters` - full example of the :paramref:`_expression.update.preserve_parameter_order` flag .. 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 " "simultaneously" ) 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:`_engine.ResultProxy.returned_defaults` accessor as a dictionary, referring to values keyed to the :class:`_schema.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 implicitly 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:`_engine.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:`_schema.Column` objects. If omitted, all column expressions evaluated on the server are added to the returning list. .. versionadded:: 0.9.0 .. seealso:: :meth:`.UpdateBase.returning` :attr:`_engine.ResultProxy.returned_defaults` """ if self._returning: raise exc.InvalidRequestError( "RETURNING is already configured on this statement" ) self._return_defaults = cols or True class Insert(ValuesBase): """Represent an INSERT construct. The :class:`_expression.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:`_expression.Insert` object. Similar functionality is available via the :meth:`_expression.TableClause.insert` method on :class:`_schema.Table`. :param table: :class:`_expression.TableClause` which is the subject of the insert. :param values: collection of values to be inserted; see :meth:`_expression.Insert.values` for a description of allowed formats here. Can be omitted entirely; a :class:`_expression.Insert` construct will also dynamically render the VALUES clause at execution time based on the parameters passed to :meth:`_engine.Connection.execute`. :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:`~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.include_insert_from_select_defaults = False 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, include_defaults=True): """Return a new :class:`_expression.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:`_schema.Column` objects representing the target columns. :param select: a :func:`_expression.select` construct, :class:`_expression.FromClause` or other construct which resolves into a :class:`_expression.FromClause`, such as an ORM :class:`_query.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. :param include_defaults: if True, non-server default values and SQL expressions as specified on :class:`_schema.Column` objects (as documented in :ref:`metadata_defaults_toplevel`) not otherwise specified in the list of names will be rendered into the INSERT and SELECT statements, so that these values are also included in the data to be inserted. .. note:: A Python-side default that uses a Python callable function will only be invoked **once** for the whole statement, and **not per row**. .. versionadded:: 1.0.0 - :meth:`_expression.Insert.from_select` now renders Python-side and SQL expression column defaults into the SELECT statement for columns otherwise not included in the list of column names. .. versionchanged:: 1.0.0 an INSERT that uses FROM SELECT implies that the :paramref:`_expression.insert.inline` flag is set to True, indicating that the statement will not attempt to fetch the "last inserted primary key" or other defaults. The statement deals with an arbitrary number of rows, so the :attr:`_engine.ResultProxy.inserted_primary_key` accessor does not apply. """ if self.parameters: raise exc.InvalidRequestError( "This construct already inserts value expressions" ) self.parameters, self._has_multi_parameters = self._process_colparams( {_column_as_key(n): Null() for n in names} ) self.select_names = names self.inline = True self.include_insert_from_select_defaults = include_defaults 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:`_expression.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, preserve_parameter_order=False, **dialect_kw ): r"""Construct an :class:`_expression.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:`_expression.TableClause.update` method on :class:`_schema.Table`:: stmt = users.update().\ where(users.c.id==5).\ values(name='user #5') :param table: A :class:`_schema.Table` object representing the database table to be updated. :param whereclause: Optional SQL expression describing the ``WHERE`` condition of the ``UPDATE`` statement; is equivalent to using the more modern :meth:`~Update.where()` method to specify the ``WHERE`` clause. :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:`_expression.Update.values` method to set the values of the UPDATE statement. :param inline: if True, SQL defaults present on :class:`_schema.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:`_engine.ResultProxy.last_updated_params`. :param preserve_parameter_order: if True, the update statement is expected to receive parameters **only** via the :meth:`_expression.Update.values` method, and they must be passed as a Python ``list`` of 2-tuples. The rendered UPDATE statement will emit the SET clause for each referenced column maintaining this order. .. versionadded:: 1.0.10 .. seealso:: :ref:`updates_order_parameters` - full example of the :paramref:`_expression.update.preserve_parameter_order` flag 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:`_schema.Column` objects or their string identifiers (specifically the "key" of the :class:`_schema.Column`, normally but not necessarily equivalent to its "name"). Normally, the :class:`_schema.Column` objects used here are expected to be part of the target :class:`_schema.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:`_schema.Column`, a scalar-returning :func:`_expression.select` construct, etc. When combining :func:`_expression.select` constructs within the values clause of an :func:`_expression.update` construct, the subquery represented by the :func:`_expression.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 """ self._preserve_parameter_order = preserve_parameter_order 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. Both :meth:`_dml.Update.where` and :meth:`_dml.Delete.where` support multiple-table forms, including database-specific ``UPDATE...FROM`` as well as ``DELETE..USING``. For backends that don't have multiple-table support, a backend agnostic approach to using multiple tables is to make use of correlated subqueries. See the linked tutorial sections below for examples. .. seealso:: :ref:`tutorial_1x_correlated_updates` :ref:`multi_table_updates` :ref:`multi_table_deletes` """ 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): froms = [] all_tables = list(sql_util.tables_from_leftmost(self.table)) seen = {all_tables[0]} 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) froms.extend(all_tables[1:]) return froms class Delete(UpdateBase): """Represent a DELETE construct. The :class:`_expression.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 ): r"""Construct :class:`_expression.Delete` object. Similar functionality is available via the :meth:`_expression.TableClause.delete` method on :class:`_schema.Table`. :param table: The table to delete rows from. :param whereclause: Optional SQL expression describing the ``WHERE`` condition of the ``DELETE`` statement; is equivalent to using the more modern :meth:`~Delete.where()` method to specify the ``WHERE`` clause. .. 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. Both :meth:`_dml.Update.where` and :meth:`_dml.Delete.where` support multiple-table forms, including database-specific ``UPDATE...FROM`` as well as ``DELETE..USING``. For backends that don't have multiple-table support, a backend agnostic approach to using multiple tables is to make use of correlated subqueries. See the linked tutorial sections below for examples. .. seealso:: :ref:`tutorial_1x_correlated_updates` :ref:`multi_table_updates` :ref:`multi_table_deletes` """ 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): froms = [] seen = {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 def _copy_internals(self, clone=_clone, **kw): # TODO: coverage self._whereclause = clone(self._whereclause, **kw)