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Diffstat (limited to 'lib/sqlalchemy/sql/events.py')
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1 files changed, 331 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/events.py b/lib/sqlalchemy/sql/events.py new file mode 100644 index 0000000..c425789 --- /dev/null +++ b/lib/sqlalchemy/sql/events.py @@ -0,0 +1,331 @@ +# sqlalchemy/sql/events.py +# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors +# <see AUTHORS file> +# +# This module is part of SQLAlchemy and is released under +# the MIT License: https://www.opensource.org/licenses/mit-license.php + +from .base import SchemaEventTarget +from .. import event + + +class DDLEvents(event.Events): + """ + Define event listeners for schema objects, + that is, :class:`.SchemaItem` and other :class:`.SchemaEventTarget` + subclasses, including :class:`_schema.MetaData`, :class:`_schema.Table`, + :class:`_schema.Column`. + + :class:`_schema.MetaData` and :class:`_schema.Table` support events + specifically regarding when CREATE and DROP + DDL is emitted to the database. + + Attachment events are also provided to customize + behavior whenever a child schema element is associated + with a parent, such as, when a :class:`_schema.Column` is associated + with its :class:`_schema.Table`, when a + :class:`_schema.ForeignKeyConstraint` + is associated with a :class:`_schema.Table`, etc. + + Example using the ``after_create`` event:: + + from sqlalchemy import event + from sqlalchemy import Table, Column, Metadata, Integer + + m = MetaData() + some_table = Table('some_table', m, Column('data', Integer)) + + def after_create(target, connection, **kw): + connection.execute(text( + "ALTER TABLE %s SET name=foo_%s" % (target.name, target.name) + )) + + event.listen(some_table, "after_create", after_create) + + DDL events integrate closely with the + :class:`.DDL` class and the :class:`.DDLElement` hierarchy + of DDL clause constructs, which are themselves appropriate + as listener callables:: + + from sqlalchemy import DDL + event.listen( + some_table, + "after_create", + DDL("ALTER TABLE %(table)s SET name=foo_%(table)s") + ) + + The methods here define the name of an event as well + as the names of members that are passed to listener + functions. + + For all :class:`.DDLEvent` events, the ``propagate=True`` keyword argument + will ensure that a given event handler is propagated to copies of the + object, which are made when using the :meth:`_schema.Table.to_metadata` + method:: + + from sqlalchemy import DDL + event.listen( + some_table, + "after_create", + DDL("ALTER TABLE %(table)s SET name=foo_%(table)s"), + propagate=True + ) + + new_table = some_table.to_metadata(new_metadata) + + The above :class:`.DDL` object will also be associated with the + :class:`_schema.Table` object represented by ``new_table``. + + .. seealso:: + + :ref:`event_toplevel` + + :class:`.DDLElement` + + :class:`.DDL` + + :ref:`schema_ddl_sequences` + + """ + + _target_class_doc = "SomeSchemaClassOrObject" + _dispatch_target = SchemaEventTarget + + def before_create(self, target, connection, **kw): + r"""Called before CREATE statements are emitted. + + :param target: the :class:`_schema.MetaData` or :class:`_schema.Table` + object which is the target of the event. + :param connection: the :class:`_engine.Connection` where the + CREATE statement or statements will be emitted. + :param \**kw: additional keyword arguments relevant + to the event. The contents of this dictionary + may vary across releases, and include the + list of tables being generated for a metadata-level + event, the checkfirst flag, and other + elements used by internal events. + + :func:`.event.listen` accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + :func:`.event.listen` accepts the ``insert=True`` + modifier for this event; when True, the listener function will + be prepended to the internal list of events upon discovery, and execute + before registered listener functions that do not pass this argument. + + """ + + def after_create(self, target, connection, **kw): + r"""Called after CREATE statements are emitted. + + :param target: the :class:`_schema.MetaData` or :class:`_schema.Table` + object which is the target of the event. + :param connection: the :class:`_engine.Connection` where the + CREATE statement or statements have been emitted. + :param \**kw: additional keyword arguments relevant + to the event. The contents of this dictionary + may vary across releases, and include the + list of tables being generated for a metadata-level + event, the checkfirst flag, and other + elements used by internal events. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + """ + + def before_drop(self, target, connection, **kw): + r"""Called before DROP statements are emitted. + + :param target: the :class:`_schema.MetaData` or :class:`_schema.Table` + object which is the target of the event. + :param connection: the :class:`_engine.Connection` where the + DROP statement or statements will be emitted. + :param \**kw: additional keyword arguments relevant + to the event. The contents of this dictionary + may vary across releases, and include the + list of tables being generated for a metadata-level + event, the checkfirst flag, and other + elements used by internal events. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + """ + + def after_drop(self, target, connection, **kw): + r"""Called after DROP statements are emitted. + + :param target: the :class:`_schema.MetaData` or :class:`_schema.Table` + object which is the target of the event. + :param connection: the :class:`_engine.Connection` where the + DROP statement or statements have been emitted. + :param \**kw: additional keyword arguments relevant + to the event. The contents of this dictionary + may vary across releases, and include the + list of tables being generated for a metadata-level + event, the checkfirst flag, and other + elements used by internal events. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + """ + + def before_parent_attach(self, target, parent): + """Called before a :class:`.SchemaItem` is associated with + a parent :class:`.SchemaItem`. + + :param target: the target object + :param parent: the parent to which the target is being attached. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + """ + + def after_parent_attach(self, target, parent): + """Called after a :class:`.SchemaItem` is associated with + a parent :class:`.SchemaItem`. + + :param target: the target object + :param parent: the parent to which the target is being attached. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + """ + + def _sa_event_column_added_to_pk_constraint(self, const, col): + """internal event hook used for primary key naming convention + updates. + + """ + + def column_reflect(self, inspector, table, column_info): + """Called for each unit of 'column info' retrieved when + a :class:`_schema.Table` is being reflected. + + This event is most easily used by applying it to a specific + :class:`_schema.MetaData` instance, where it will take effect for + all :class:`_schema.Table` objects within that + :class:`_schema.MetaData` that undergo reflection:: + + metadata = MetaData() + + @event.listens_for(metadata, 'column_reflect') + def receive_column_reflect(inspector, table, column_info): + # receives for all Table objects that are reflected + # under this MetaData + + + # will use the above event hook + my_table = Table("my_table", metadata, autoload_with=some_engine) + + + .. versionadded:: 1.4.0b2 The :meth:`_events.DDLEvents.column_reflect` + hook may now be applied to a :class:`_schema.MetaData` object as + well as the :class:`_schema.MetaData` class itself where it will + take place for all :class:`_schema.Table` objects associated with + the targeted :class:`_schema.MetaData`. + + It may also be applied to the :class:`_schema.Table` class across + the board:: + + from sqlalchemy import Table + + @event.listens_for(Table, 'column_reflect') + def receive_column_reflect(inspector, table, column_info): + # receives for all Table objects that are reflected + + It can also be applied to a specific :class:`_schema.Table` at the + point that one is being reflected using the + :paramref:`_schema.Table.listeners` parameter:: + + t1 = Table( + "my_table", + autoload_with=some_engine, + listeners=[ + ('column_reflect', receive_column_reflect) + ] + ) + + A future release will allow it to be associated with a specific + :class:`_schema.MetaData` object as well. + + The dictionary of column information as returned by the + dialect is passed, and can be modified. The dictionary + is that returned in each element of the list returned + by :meth:`.reflection.Inspector.get_columns`: + + * ``name`` - the column's name, is applied to the + :paramref:`_schema.Column.name` parameter + + * ``type`` - the type of this column, which should be an instance + of :class:`~sqlalchemy.types.TypeEngine`, is applied to the + :paramref:`_schema.Column.type` parameter + + * ``nullable`` - boolean flag if the column is NULL or NOT NULL, + is applied to the :paramref:`_schema.Column.nullable` parameter + + * ``default`` - the column's server default value. This is + normally specified as a plain string SQL expression, however the + event can pass a :class:`.FetchedValue`, :class:`.DefaultClause`, + or :func:`_expression.text` object as well. Is applied to the + :paramref:`_schema.Column.server_default` parameter + + The event is called before any action is taken against + this dictionary, and the contents can be modified; the following + additional keys may be added to the dictionary to further modify + how the :class:`_schema.Column` is constructed: + + + * ``key`` - the string key that will be used to access this + :class:`_schema.Column` in the ``.c`` collection; will be applied + to the :paramref:`_schema.Column.key` parameter. Is also used + for ORM mapping. See the section + :ref:`mapper_automated_reflection_schemes` for an example. + + * ``quote`` - force or un-force quoting on the column name; + is applied to the :paramref:`_schema.Column.quote` parameter. + + * ``info`` - a dictionary of arbitrary data to follow along with + the :class:`_schema.Column`, is applied to the + :paramref:`_schema.Column.info` parameter. + + :func:`.event.listen` also accepts the ``propagate=True`` + modifier for this event; when True, the listener function will + be established for any copies made of the target object, + i.e. those copies that are generated when + :meth:`_schema.Table.to_metadata` is used. + + .. seealso:: + + :ref:`mapper_automated_reflection_schemes` - + in the ORM mapping documentation + + :ref:`automap_intercepting_columns` - + in the :ref:`automap_toplevel` documentation + + :ref:`metadata_reflection_dbagnostic_types` - in + the :ref:`metadata_reflection_toplevel` documentation + + """ |