我们从Python开源项目中，提取了以下30个代码示例，用于说明如何使用sqlalchemy.func.len()。
def upgrade_ops(self): """An instance of :class:`.UpgradeOps`. .. seealso:: :attr:`.MigrationScript.upgrade_ops_list` """ if len(self._upgrade_ops) > 1: raise ValueError( "This MigrationScript instance has a multiple-entry " "list for UpgradeOps; please use the " "upgrade_ops_list attribute.") elif not self._upgrade_ops: return None else: return self._upgrade_ops[0]
def downgrade_ops(self): """An instance of :class:`.DowngradeOps`. .. seealso:: :attr:`.MigrationScript.downgrade_ops_list` """ if len(self._downgrade_ops) > 1: raise ValueError( "This MigrationScript instance has a multiple-entry " "list for DowngradeOps; please use the " "downgrade_ops_list attribute.") elif not self._downgrade_ops: return None else: return self._downgrade_ops[0]
def create_check_constraint( cls, operations, constraint_name, table_name, condition, schema=None, **kw): """Issue a "create check constraint" instruction using the current migration context. e.g.:: from alembic import op from sqlalchemy.sql import column, func op.create_check_constraint( "ck_user_name_len", "user", func.len(column('name')) > 5 ) CHECK constraints are usually against a SQL expression, so ad-hoc table metadata is usually needed. The function will convert the given arguments into a :class:`sqlalchemy.schema.CheckConstraint` bound to an anonymous table in order to emit the CREATE statement. :param name: Name of the check constraint. The name is necessary so that an ALTER statement can be emitted. For setups that use an automated naming scheme such as that described at :ref:`sqla:constraint_naming_conventions`, ``name`` here can be ``None``, as the event listener will apply the name to the constraint object when it is associated with the table. :param table_name: String name of the source table. :param condition: SQL expression that's the condition of the constraint. Can be a string or SQLAlchemy expression language structure. :param deferrable: optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when issuing DDL for this constraint. :param initially: optional string. If set, emit INITIALLY <value> when issuing DDL for this constraint. :param schema: Optional schema name to operate within. To control quoting of the schema outside of the default behavior, use the SQLAlchemy construct :class:`~sqlalchemy.sql.elements.quoted_name`. .. versionadded:: 0.7.0 'schema' can now accept a :class:`~sqlalchemy.sql.elements.quoted_name` construct. .. versionchanged:: 0.8.0 The following positional argument names have been changed: * name -> constraint_name * source -> table_name """ op = cls(constraint_name, table_name, condition, schema=schema, **kw) return operations.invoke(op)
def create_check_constraint(self, name, source, condition, schema=None, **kw): """Issue a "create check constraint" instruction using the current migration context. e.g.:: from alembic import op from sqlalchemy.sql import column, func op.create_check_constraint( "ck_user_name_len", "user", func.len(column('name')) > 5 ) CHECK constraints are usually against a SQL expression, so ad-hoc table metadata is usually needed. The function will convert the given arguments into a :class:`sqlalchemy.schema.CheckConstraint` bound to an anonymous table in order to emit the CREATE statement. :param name: Name of the check constraint. The name is necessary so that an ALTER statement can be emitted. For setups that use an automated naming scheme such as that described at `NamingConventions <http://www.sqlalchemy.org/trac/wiki/UsageRecipes/NamingConventions>`_, ``name`` here can be ``None``, as the event listener will apply the name to the constraint object when it is associated with the table. :param source: String name of the source table. :param condition: SQL expression that's the condition of the constraint. Can be a string or SQLAlchemy expression language structure. :param deferrable: optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when issuing DDL for this constraint. :param initially: optional string. If set, emit INITIALLY <value> when issuing DDL for this constraint. :param schema: Optional schema name to operate within. ..versionadded:: 0.4.0 """ self.impl.add_constraint( self._check_constraint(name, source, condition, schema=schema, **kw) )
def create_check_constraint(self, name, source, condition, schema=None, **kw): """Issue a "create check constraint" instruction using the current migration context. e.g.:: from alembic import op from sqlalchemy.sql import column, func op.create_check_constraint( "ck_user_name_len", "user", func.len(column('name')) > 5 ) CHECK constraints are usually against a SQL expression, so ad-hoc table metadata is usually needed. The function will convert the given arguments into a :class:`sqlalchemy.schema.CheckConstraint` bound to an anonymous table in order to emit the CREATE statement. :param name: Name of the check constraint. The name is necessary so that an ALTER statement can be emitted. For setups that use an automated naming scheme such as that described at :ref:`sqla:constraint_naming_conventions`, ``name`` here can be ``None``, as the event listener will apply the name to the constraint object when it is associated with the table. :param source: String name of the source table. :param condition: SQL expression that's the condition of the constraint. Can be a string or SQLAlchemy expression language structure. :param deferrable: optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when issuing DDL for this constraint. :param initially: optional string. If set, emit INITIALLY <value> when issuing DDL for this constraint. :param schema: Optional schema name to operate within. To control quoting of the schema outside of the default behavior, use the SQLAlchemy construct :class:`~sqlalchemy.sql.elements.quoted_name`. .. versionadded:: 0.7.0 'schema' can now accept a :class:`~sqlalchemy.sql.elements.quoted_name` construct. """ self.impl.add_constraint( self._check_constraint( name, source, condition, schema=schema, **kw) )
