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"""
Support for MS-SQL via pyodbc.
http://pypi.python.org/pypi/pyodbc/
Connect strings are of the form::
mssql+pyodbc://<username>:<password>@<dsn>/
mssql+pyodbc://<username>:<password>@<host>/<database>
"""
from sqlalchemy.dialects.mssql.base import MSExecutionContext, MSDialect
from sqlalchemy.connectors.pyodbc import PyODBCConnector
from sqlalchemy import types as sqltypes
import re
import sys
class MSExecutionContext_pyodbc(MSExecutionContext):
_embedded_scope_identity = False
def pre_exec(self):
"""where appropriate, issue "select scope_identity()" in the same statement.
Background on why "scope_identity()" is preferable to "@@identity":
http://msdn.microsoft.com/en-us/library/ms190315.aspx
Background on why we attempt to embed "scope_identity()" into the same
statement as the INSERT:
http://code.google.com/p/pyodbc/wiki/FAQs#How_do_I_retrieve_autogenerated/identity_values?
"""
super(MSExecutionContext_pyodbc, self).pre_exec()
# don't embed the scope_identity select into an "INSERT .. DEFAULT VALUES"
if self._select_lastrowid and \
self.dialect.use_scope_identity and \
len(self.parameters[0]):
self._embedded_scope_identity = True
self.statement += "; select scope_identity()"
def post_exec(self):
if self._embedded_scope_identity:
# Fetch the last inserted id from the manipulated statement
# We may have to skip over a number of result sets with no data (due to triggers, etc.)
while True:
try:
# fetchall() ensures the cursor is consumed
# without closing it (FreeTDS particularly)
row = self.cursor.fetchall()[0]
break
except self.dialect.dbapi.Error, e:
# no way around this - nextset() consumes the previous set
# so we need to just keep flipping
self.cursor.nextset()
self._lastrowid = int(row[0])
else:
super(MSExecutionContext_pyodbc, self).post_exec()
class MSDialect_pyodbc(PyODBCConnector, MSDialect):
execution_ctx_cls = MSExecutionContext_pyodbc
pyodbc_driver_name = 'SQL Server'
def __init__(self, description_encoding='latin-1', **params):
super(MSDialect_pyodbc, self).__init__(**params)
self.description_encoding = description_encoding
self.use_scope_identity = self.dbapi and hasattr(self.dbapi.Cursor, 'nextset')
dialect = MSDialect_pyodbc
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