# sql/dml.py # Copyright (C) 2009-2014 the SQLAlchemy authors and contributors # # # 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() `_ 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. .. note:: Depending on backend, it may be necessary for the :class:`.Insert` statement to be constructed using the ``inline=True`` flag; this flag will prevent the implicit usage of ``RETURNING`` when the ``INSERT`` statement is rendered, which isn't supported on a backend such as Oracle in conjunction with an ``INSERT..SELECT`` combination:: sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5) ins = table2.insert(inline=True).from_select(['a', 'b'], sel) .. note:: A SELECT..INSERT construct in SQL has no VALUES clause. Therefore :class:`.Column` objects which utilize Python-side defaults (e.g. as described at :ref:`metadata_defaults_toplevel`) will **not** take effect when using :meth:`.Insert.from_select`. .. 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, 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)