Classe « Computed »

Constructeur sqlalchemy.Computed.__init__

Signature de la constructeur __init__

def __init__(self, sqltext, persisted=None) 

Description

__init__.__doc__

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

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

          .. warning:: The :paramref:`.Computed.sqltext` argument to :class:`.Computed` can be passed as a Python string argument, which will be treated as **trusted SQL text** and rendered as given.  **DO NOT PASS UNTRUSTED INPUT TO THIS PARAMETER**.



        :param 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``.