Executable
is a class within the sqlalchemy.sql.expression
module of the SQLAlchemy project.
ClauseElement,
ColumnClause,
ColumnElement,
FunctionElement,
and UnaryExpression
are several other callables with code examples from the same sqlalchemy.sql.expression
package.
Alembic (project documentation and PyPI page) is a data migrations tool used with SQLAlchemy to make database schema changes. The Alembic project is open sourced under the MIT license.
alembic / alembic / ddl / mssql.py
# mssql.py
from sqlalchemy import types as sqltypes
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.schema import Column
from sqlalchemy.schema import CreateIndex
from sqlalchemy.sql.expression import ClauseElement
from sqlalchemy.sql.expression import Executable
from .base import AddColumn
from .base import alter_column
from .base import alter_table
from .base import ColumnDefault
from .base import ColumnName
from .base import ColumnNullable
from .base import ColumnType
from .base import format_column_name
from .base import format_server_default
from .base import format_table_name
from .base import format_type
from .base import RenameTable
from .impl import DefaultImpl
from .. import util
class MSSQLImpl(DefaultImpl):
__dialect__ = "mssql"
transactional_ddl = True
batch_separator = "GO"
type_synonyms = DefaultImpl.type_synonyms + ({"VARCHAR", "NVARCHAR"},)
## ... source file abbreviated to get to Executable examples ...
super(MSSQLImpl, self).bulk_insert(table, rows, **kw)
def drop_column(self, table_name, column, schema=None, **kw):
drop_default = kw.pop("mssql_drop_default", False)
if drop_default:
self._exec(
_ExecDropConstraint(
table_name, column, "sys.default_constraints", schema
)
)
drop_check = kw.pop("mssql_drop_check", False)
if drop_check:
self._exec(
_ExecDropConstraint(
table_name, column, "sys.check_constraints", schema
)
)
drop_fks = kw.pop("mssql_drop_foreign_key", False)
if drop_fks:
self._exec(_ExecDropFKConstraint(table_name, column, schema))
super(MSSQLImpl, self).drop_column(
table_name, column, schema=schema, **kw
)
class _ExecDropConstraint(Executable, ClauseElement):
def __init__(self, tname, colname, type_, schema):
self.tname = tname
self.colname = colname
self.type_ = type_
self.schema = schema
class _ExecDropFKConstraint(Executable, ClauseElement):
def __init__(self, tname, colname, schema):
self.tname = tname
self.colname = colname
self.schema = schema
@compiles(_ExecDropConstraint, "mssql")
def _exec_drop_col_constraint(element, compiler, **kw):
schema, tname, colname, type_ = (
element.schema,
element.tname,
element.colname,
element.type_,
)
return """declare @const_name varchar(256)
select @const_name = [name] from %(type)s
where parent_object_id = object_id('%(schema_dot)s%(tname)s')
and col_name(parent_object_id, parent_column_id) = '%(colname)s'
exec('alter table %(tname_quoted)s drop constraint ' + @const_name)""" % {
"type": type_,
"tname": tname,
"colname": colname,
"tname_quoted": format_table_name(compiler, tname, schema),
"schema_dot": schema + "." if schema else "",
## ... source file continues with no further Executable examples...