Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/sqlalchemy/sql/events.py: 100%
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1# sqlalchemy/sql/events.py
2# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
3# <see AUTHORS file>
4#
5# This module is part of SQLAlchemy and is released under
6# the MIT License: https://www.opensource.org/licenses/mit-license.php
8from .base import SchemaEventTarget
9from .. import event
12class DDLEvents(event.Events):
13 """
14 Define event listeners for schema objects,
15 that is, :class:`.SchemaItem` and other :class:`.SchemaEventTarget`
16 subclasses, including :class:`_schema.MetaData`, :class:`_schema.Table`,
17 :class:`_schema.Column`.
19 :class:`_schema.MetaData` and :class:`_schema.Table` support events
20 specifically regarding when CREATE and DROP
21 DDL is emitted to the database.
23 Attachment events are also provided to customize
24 behavior whenever a child schema element is associated
25 with a parent, such as, when a :class:`_schema.Column` is associated
26 with its :class:`_schema.Table`, when a
27 :class:`_schema.ForeignKeyConstraint`
28 is associated with a :class:`_schema.Table`, etc.
30 Example using the ``after_create`` event::
32 from sqlalchemy import event
33 from sqlalchemy import Table, Column, Metadata, Integer
35 m = MetaData()
36 some_table = Table('some_table', m, Column('data', Integer))
38 def after_create(target, connection, **kw):
39 connection.execute(text(
40 "ALTER TABLE %s SET name=foo_%s" % (target.name, target.name)
41 ))
43 event.listen(some_table, "after_create", after_create)
45 DDL events integrate closely with the
46 :class:`.DDL` class and the :class:`.DDLElement` hierarchy
47 of DDL clause constructs, which are themselves appropriate
48 as listener callables::
50 from sqlalchemy import DDL
51 event.listen(
52 some_table,
53 "after_create",
54 DDL("ALTER TABLE %(table)s SET name=foo_%(table)s")
55 )
57 The methods here define the name of an event as well
58 as the names of members that are passed to listener
59 functions.
61 For all :class:`.DDLEvent` events, the ``propagate=True`` keyword argument
62 will ensure that a given event handler is propagated to copies of the
63 object, which are made when using the :meth:`_schema.Table.to_metadata`
64 method::
66 from sqlalchemy import DDL
67 event.listen(
68 some_table,
69 "after_create",
70 DDL("ALTER TABLE %(table)s SET name=foo_%(table)s"),
71 propagate=True
72 )
74 new_table = some_table.to_metadata(new_metadata)
76 The above :class:`.DDL` object will also be associated with the
77 :class:`_schema.Table` object represented by ``new_table``.
79 .. seealso::
81 :ref:`event_toplevel`
83 :class:`.DDLElement`
85 :class:`.DDL`
87 :ref:`schema_ddl_sequences`
89 """
91 _target_class_doc = "SomeSchemaClassOrObject"
92 _dispatch_target = SchemaEventTarget
94 def before_create(self, target, connection, **kw):
95 r"""Called before CREATE statements are emitted.
97 :param target: the :class:`_schema.MetaData` or :class:`_schema.Table`
98 object which is the target of the event.
99 :param connection: the :class:`_engine.Connection` where the
100 CREATE statement or statements will be emitted.
101 :param \**kw: additional keyword arguments relevant
102 to the event. The contents of this dictionary
103 may vary across releases, and include the
104 list of tables being generated for a metadata-level
105 event, the checkfirst flag, and other
106 elements used by internal events.
108 :func:`.event.listen` accepts the ``propagate=True``
109 modifier for this event; when True, the listener function will
110 be established for any copies made of the target object,
111 i.e. those copies that are generated when
112 :meth:`_schema.Table.to_metadata` is used.
114 :func:`.event.listen` accepts the ``insert=True``
115 modifier for this event; when True, the listener function will
116 be prepended to the internal list of events upon discovery, and execute
117 before registered listener functions that do not pass this argument.
119 """
121 def after_create(self, target, connection, **kw):
122 r"""Called after CREATE statements are emitted.
124 :param target: the :class:`_schema.MetaData` or :class:`_schema.Table`
125 object which is the target of the event.
126 :param connection: the :class:`_engine.Connection` where the
127 CREATE statement or statements have been emitted.
128 :param \**kw: additional keyword arguments relevant
129 to the event. The contents of this dictionary
130 may vary across releases, and include the
131 list of tables being generated for a metadata-level
132 event, the checkfirst flag, and other
133 elements used by internal events.
135 :func:`.event.listen` also accepts the ``propagate=True``
136 modifier for this event; when True, the listener function will
137 be established for any copies made of the target object,
138 i.e. those copies that are generated when
139 :meth:`_schema.Table.to_metadata` is used.
141 """
143 def before_drop(self, target, connection, **kw):
144 r"""Called before DROP statements are emitted.
146 :param target: the :class:`_schema.MetaData` or :class:`_schema.Table`
147 object which is the target of the event.
148 :param connection: the :class:`_engine.Connection` where the
149 DROP statement or statements will be emitted.
150 :param \**kw: additional keyword arguments relevant
151 to the event. The contents of this dictionary
152 may vary across releases, and include the
153 list of tables being generated for a metadata-level
154 event, the checkfirst flag, and other
155 elements used by internal events.
157 :func:`.event.listen` also accepts the ``propagate=True``
158 modifier for this event; when True, the listener function will
159 be established for any copies made of the target object,
160 i.e. those copies that are generated when
161 :meth:`_schema.Table.to_metadata` is used.
163 """
165 def after_drop(self, target, connection, **kw):
166 r"""Called after DROP statements are emitted.
168 :param target: the :class:`_schema.MetaData` or :class:`_schema.Table`
169 object which is the target of the event.
170 :param connection: the :class:`_engine.Connection` where the
171 DROP statement or statements have been emitted.
172 :param \**kw: additional keyword arguments relevant
173 to the event. The contents of this dictionary
174 may vary across releases, and include the
175 list of tables being generated for a metadata-level
176 event, the checkfirst flag, and other
177 elements used by internal events.
179 :func:`.event.listen` also accepts the ``propagate=True``
180 modifier for this event; when True, the listener function will
181 be established for any copies made of the target object,
182 i.e. those copies that are generated when
183 :meth:`_schema.Table.to_metadata` is used.
185 """
187 def before_parent_attach(self, target, parent):
188 """Called before a :class:`.SchemaItem` is associated with
189 a parent :class:`.SchemaItem`.
191 :param target: the target object
192 :param parent: the parent to which the target is being attached.
194 :func:`.event.listen` also accepts the ``propagate=True``
195 modifier for this event; when True, the listener function will
196 be established for any copies made of the target object,
197 i.e. those copies that are generated when
198 :meth:`_schema.Table.to_metadata` is used.
200 """
202 def after_parent_attach(self, target, parent):
203 """Called after a :class:`.SchemaItem` is associated with
204 a parent :class:`.SchemaItem`.
206 :param target: the target object
207 :param parent: the parent to which the target is being attached.
209 :func:`.event.listen` also accepts the ``propagate=True``
210 modifier for this event; when True, the listener function will
211 be established for any copies made of the target object,
212 i.e. those copies that are generated when
213 :meth:`_schema.Table.to_metadata` is used.
215 """
217 def _sa_event_column_added_to_pk_constraint(self, const, col):
218 """internal event hook used for primary key naming convention
219 updates.
221 """
223 def column_reflect(self, inspector, table, column_info):
224 """Called for each unit of 'column info' retrieved when
225 a :class:`_schema.Table` is being reflected.
227 This event is most easily used by applying it to a specific
228 :class:`_schema.MetaData` instance, where it will take effect for
229 all :class:`_schema.Table` objects within that
230 :class:`_schema.MetaData` that undergo reflection::
232 metadata = MetaData()
234 @event.listens_for(metadata, 'column_reflect')
235 def receive_column_reflect(inspector, table, column_info):
236 # receives for all Table objects that are reflected
237 # under this MetaData
240 # will use the above event hook
241 my_table = Table("my_table", metadata, autoload_with=some_engine)
244 .. versionadded:: 1.4.0b2 The :meth:`_events.DDLEvents.column_reflect`
245 hook may now be applied to a :class:`_schema.MetaData` object as
246 well as the :class:`_schema.MetaData` class itself where it will
247 take place for all :class:`_schema.Table` objects associated with
248 the targeted :class:`_schema.MetaData`.
250 It may also be applied to the :class:`_schema.Table` class across
251 the board::
253 from sqlalchemy import Table
255 @event.listens_for(Table, 'column_reflect')
256 def receive_column_reflect(inspector, table, column_info):
257 # receives for all Table objects that are reflected
259 It can also be applied to a specific :class:`_schema.Table` at the
260 point that one is being reflected using the
261 :paramref:`_schema.Table.listeners` parameter::
263 t1 = Table(
264 "my_table",
265 autoload_with=some_engine,
266 listeners=[
267 ('column_reflect', receive_column_reflect)
268 ]
269 )
271 The dictionary of column information as returned by the
272 dialect is passed, and can be modified. The dictionary
273 is that returned in each element of the list returned
274 by :meth:`.reflection.Inspector.get_columns`:
276 * ``name`` - the column's name, is applied to the
277 :paramref:`_schema.Column.name` parameter
279 * ``type`` - the type of this column, which should be an instance
280 of :class:`~sqlalchemy.types.TypeEngine`, is applied to the
281 :paramref:`_schema.Column.type` parameter
283 * ``nullable`` - boolean flag if the column is NULL or NOT NULL,
284 is applied to the :paramref:`_schema.Column.nullable` parameter
286 * ``default`` - the column's server default value. This is
287 normally specified as a plain string SQL expression, however the
288 event can pass a :class:`.FetchedValue`, :class:`.DefaultClause`,
289 or :func:`_expression.text` object as well. Is applied to the
290 :paramref:`_schema.Column.server_default` parameter
292 The event is called before any action is taken against
293 this dictionary, and the contents can be modified; the following
294 additional keys may be added to the dictionary to further modify
295 how the :class:`_schema.Column` is constructed:
298 * ``key`` - the string key that will be used to access this
299 :class:`_schema.Column` in the ``.c`` collection; will be applied
300 to the :paramref:`_schema.Column.key` parameter. Is also used
301 for ORM mapping. See the section
302 :ref:`mapper_automated_reflection_schemes` for an example.
304 * ``quote`` - force or un-force quoting on the column name;
305 is applied to the :paramref:`_schema.Column.quote` parameter.
307 * ``info`` - a dictionary of arbitrary data to follow along with
308 the :class:`_schema.Column`, is applied to the
309 :paramref:`_schema.Column.info` parameter.
311 :func:`.event.listen` also accepts the ``propagate=True``
312 modifier for this event; when True, the listener function will
313 be established for any copies made of the target object,
314 i.e. those copies that are generated when
315 :meth:`_schema.Table.to_metadata` is used.
317 .. seealso::
319 :ref:`mapper_automated_reflection_schemes` -
320 in the ORM mapping documentation
322 :ref:`automap_intercepting_columns` -
323 in the :ref:`automap_toplevel` documentation
325 :ref:`metadata_reflection_dbagnostic_types` - in
326 the :ref:`metadata_reflection_toplevel` documentation
328 """