sqlalchemy.sql.expression Executable Example Code

# 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 "",


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