198 lines
6.9 KiB
Python
198 lines
6.9 KiB
Python
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"""
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Support for MS-SQL via pyodbc.
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pyodbc is available at:
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http://pypi.python.org/pypi/pyodbc/
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Connecting
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^^^^^^^^^^
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Examples of pyodbc connection string URLs:
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* ``mssql+pyodbc://mydsn`` - connects using the specified DSN named ``mydsn``.
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The connection string that is created will appear like::
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dsn=mydsn;Trusted_Connection=Yes
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* ``mssql+pyodbc://user:pass@mydsn`` - connects using the DSN named
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``mydsn`` passing in the ``UID`` and ``PWD`` information. The
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connection string that is created will appear like::
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dsn=mydsn;UID=user;PWD=pass
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* ``mssql+pyodbc://user:pass@mydsn/?LANGUAGE=us_english`` - connects
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using the DSN named ``mydsn`` passing in the ``UID`` and ``PWD``
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information, plus the additional connection configuration option
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``LANGUAGE``. The connection string that is created will appear
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like::
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dsn=mydsn;UID=user;PWD=pass;LANGUAGE=us_english
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* ``mssql+pyodbc://user:pass@host/db`` - connects using a connection string
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dynamically created that would appear like::
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DRIVER={SQL Server};Server=host;Database=db;UID=user;PWD=pass
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* ``mssql+pyodbc://user:pass@host:123/db`` - connects using a connection
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string that is dynamically created, which also includes the port
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information using the comma syntax. If your connection string
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requires the port information to be passed as a ``port`` keyword
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see the next example. This will create the following connection
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string::
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DRIVER={SQL Server};Server=host,123;Database=db;UID=user;PWD=pass
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* ``mssql+pyodbc://user:pass@host/db?port=123`` - connects using a connection
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string that is dynamically created that includes the port
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information as a separate ``port`` keyword. This will create the
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following connection string::
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DRIVER={SQL Server};Server=host;Database=db;UID=user;PWD=pass;port=123
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If you require a connection string that is outside the options
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presented above, use the ``odbc_connect`` keyword to pass in a
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urlencoded connection string. What gets passed in will be urldecoded
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and passed directly.
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For example::
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mssql+pyodbc:///?odbc_connect=dsn%3Dmydsn%3BDatabase%3Ddb
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would create the following connection string::
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dsn=mydsn;Database=db
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Encoding your connection string can be easily accomplished through
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the python shell. For example::
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>>> import urllib
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>>> urllib.quote_plus('dsn=mydsn;Database=db')
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'dsn%3Dmydsn%3BDatabase%3Ddb'
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"""
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from sqlalchemy.dialects.mssql.base import MSExecutionContext, MSDialect
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from sqlalchemy.connectors.pyodbc import PyODBCConnector
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from sqlalchemy import types as sqltypes, util
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import decimal
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class _MSNumeric_pyodbc(sqltypes.Numeric):
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"""Turns Decimals with adjusted() < 0 or > 7 into strings.
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This is the only method that is proven to work with Pyodbc+MSSQL
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without crashing (floats can be used but seem to cause sporadic
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crashes).
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"""
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def bind_processor(self, dialect):
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super_process = super(_MSNumeric_pyodbc, self).bind_processor(dialect)
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def process(value):
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if self.asdecimal and \
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isinstance(value, decimal.Decimal):
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adjusted = value.adjusted()
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if adjusted < 0:
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return self._small_dec_to_string(value)
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elif adjusted > 7:
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return self._large_dec_to_string(value)
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if super_process:
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return super_process(value)
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else:
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return value
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return process
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def _small_dec_to_string(self, value):
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return "%s0.%s%s" % (
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(value < 0 and '-' or ''),
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'0' * (abs(value.adjusted()) - 1),
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"".join([str(nint) for nint in value._int]))
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def _large_dec_to_string(self, value):
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if 'E' in str(value):
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result = "%s%s%s" % (
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(value < 0 and '-' or ''),
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"".join([str(s) for s in value._int]),
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"0" * (value.adjusted() - (len(value._int)-1)))
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else:
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if (len(value._int) - 1) > value.adjusted():
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result = "%s%s.%s" % (
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(value < 0 and '-' or ''),
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"".join([str(s) for s in value._int][0:value.adjusted() + 1]),
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"".join([str(s) for s in value._int][value.adjusted() + 1:]))
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else:
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result = "%s%s" % (
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(value < 0 and '-' or ''),
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"".join([str(s) for s in value._int][0:value.adjusted() + 1]))
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return result
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class MSExecutionContext_pyodbc(MSExecutionContext):
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_embedded_scope_identity = False
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def pre_exec(self):
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"""where appropriate, issue "select scope_identity()" in the same statement.
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Background on why "scope_identity()" is preferable to "@@identity":
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http://msdn.microsoft.com/en-us/library/ms190315.aspx
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Background on why we attempt to embed "scope_identity()" into the same
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statement as the INSERT:
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http://code.google.com/p/pyodbc/wiki/FAQs#How_do_I_retrieve_autogenerated/identity_values?
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"""
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super(MSExecutionContext_pyodbc, self).pre_exec()
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# don't embed the scope_identity select into an "INSERT .. DEFAULT VALUES"
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if self._select_lastrowid and \
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self.dialect.use_scope_identity and \
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len(self.parameters[0]):
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self._embedded_scope_identity = True
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self.statement += "; select scope_identity()"
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def post_exec(self):
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if self._embedded_scope_identity:
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# Fetch the last inserted id from the manipulated statement
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# We may have to skip over a number of result sets with no data (due to triggers, etc.)
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while True:
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try:
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# fetchall() ensures the cursor is consumed
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# without closing it (FreeTDS particularly)
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row = self.cursor.fetchall()[0]
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break
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except self.dialect.dbapi.Error, e:
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# no way around this - nextset() consumes the previous set
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# so we need to just keep flipping
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self.cursor.nextset()
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self._lastrowid = int(row[0])
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else:
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super(MSExecutionContext_pyodbc, self).post_exec()
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class MSDialect_pyodbc(PyODBCConnector, MSDialect):
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execution_ctx_cls = MSExecutionContext_pyodbc
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pyodbc_driver_name = 'SQL Server'
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colspecs = util.update_copy(
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MSDialect.colspecs,
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{
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sqltypes.Numeric:_MSNumeric_pyodbc
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}
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)
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def __init__(self, description_encoding='latin-1', **params):
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super(MSDialect_pyodbc, self).__init__(**params)
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self.description_encoding = description_encoding
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self.use_scope_identity = self.dbapi and hasattr(self.dbapi.Cursor, 'nextset')
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dialect = MSDialect_pyodbc
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