sqlalchemy.sql.schema.Computed

class documentation

class Computed(FetchedValue, SchemaItem):

Defines a generated column, i.e. "GENERATED ALWAYS AS" syntax.

The .Computed construct is an inline construct added to the argument list of a _schema.Column object:

from sqlalchemy import Computed

Table('square', metadata_obj,
    Column('side', Float, nullable=False),
    Column('area', Float, Computed('side * side'))
)

See the linked documentation below for complete details.

New in version 1.3.11.

See Also

:ref:`computed_ddl`

Method	`__init__`	Construct a GENERATED ALWAYS AS DDL construct to accompany a `_schema.Column`.
Method	`_as_for_update`	Undocumented
Method	`_copy`	Undocumented
Method	`_set_parent`	Associate with this SchemaEvent's parent object.
Method	`copy`	Undocumented
Class Variable	`__visit_name__`	Undocumented
Instance Variable	`column`	Undocumented
Instance Variable	`persisted`	Undocumented
Instance Variable	`sqltext`	Undocumented

Inherited from FetchedValue:

Method	`__repr__`	Undocumented
Method	`_clone`	Undocumented
Class Variable	`has_argument`	Undocumented
Class Variable	`is_clause_element`	Undocumented
Class Variable	`is_server_default`	Undocumented
Class Variable	`reflected`	Undocumented
Instance Variable	`for_update`	Undocumented

Inherited from SchemaEventTarget (via FetchedValue):

Method _set_parent_with_dispatch Undocumented

Inherited from SchemaItem:

Method	`__repr__`	Undocumented
Method	`_init_items`	Initialize the list of child items for this SchemaItem.
Method	`_schema_item_copy`	Undocumented
Class Variable	`_use_schema_map`	Undocumented
Class Variable	`create_drop_stringify_dialect`	Undocumented
Property	`info`	Info dictionary associated with the object, allowing user-defined data to be associated with this `.SchemaItem`.

Inherited from SchemaEventTarget (via SchemaItem):

Method _set_parent_with_dispatch Undocumented

Inherited from Traversible (via SchemaItem):

Method	`get_children`	Return immediate child `.visitors.Traversible` elements of this `.visitors.Traversible`.
Method	`__class_getitem__`	Undocumented

@_document_text_coercion('sqltext', ':class:`.Computed`', ':paramref:`.Computed.sqltext`')
def __init__(self, sqltext, persisted=None):

overrides sqlalchemy.sql.schema.FetchedValue.__init__

Construct a GENERATED ALWAYS AS DDL construct to accompany a _schema.Column.

Parameters

sqltext A string containing the column generation expression, which will be used verbatim, or a SQL expression construct, such as a _expression.text object. If given as a string, the object is converted to a _expression.text object.

persisted

Optional, controls how this column should be persisted by the database. Possible values are:

None, the default, it will use the default persistence defined by the database.
True, will render GENERATED ALWAYS AS ... STORED, or the equivalent for the target database if supported.
False, will render GENERATED ALWAYS AS ... VIRTUAL, or the equivalent for the target database if supported.

Specifying True or False may raise an error when the DDL is emitted to the target database if the database does not support that persistence option. Leaving this parameter at its default of None is guaranteed to succeed for all databases that support GENERATED ALWAYS AS.

def _as_for_update(self, for_update):

overrides sqlalchemy.sql.schema.FetchedValue._as_for_update

Undocumented

def _copy(self, target_table=None, **kw):

Undocumented

def _set_parent(self, parent, **kw):

overrides sqlalchemy.sql.schema.FetchedValue._set_parent

Associate with this SchemaEvent's parent object.

@util.deprecated('1.4', 'The :meth:`_schema.Computed.copy` method is deprecated and will be removed in a future release.')
def copy(self, target_table=None, **kw):

Undocumented

__visit_name__: str =

overrides sqlalchemy.sql.schema.SchemaItem.__visit_name__

Undocumented

column =

overrides sqlalchemy.sql.schema.FetchedValue.column

Undocumented

persisted =

Undocumented

sqltext =

Undocumented