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113 lines
4.0 KiB
Python
113 lines
4.0 KiB
Python
3 months ago
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# firebird/fdb.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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"""
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.. dialect:: firebird+fdb
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:name: fdb
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:dbapi: pyodbc
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:connectstring: firebird+fdb://user:password@host:port/path/to/db[?key=value&key=value...]
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:url: https://pypi.org/project/fdb/
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fdb is a kinterbasdb compatible DBAPI for Firebird.
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.. versionchanged:: 0.9 - The fdb dialect is now the default dialect
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under the ``firebird://`` URL space, as ``fdb`` is now the official
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Python driver for Firebird.
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Arguments
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----------
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The ``fdb`` dialect is based on the
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:mod:`sqlalchemy.dialects.firebird.kinterbasdb` dialect, however does not
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accept every argument that Kinterbasdb does.
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* ``enable_rowcount`` - True by default, setting this to False disables
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the usage of "cursor.rowcount" with the
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Kinterbasdb dialect, which SQLAlchemy ordinarily calls upon automatically
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after any UPDATE or DELETE statement. When disabled, SQLAlchemy's
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CursorResult will return -1 for result.rowcount. The rationale here is
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that Kinterbasdb requires a second round trip to the database when
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.rowcount is called - since SQLA's resultproxy automatically closes
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the cursor after a non-result-returning statement, rowcount must be
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called, if at all, before the result object is returned. Additionally,
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cursor.rowcount may not return correct results with older versions
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of Firebird, and setting this flag to False will also cause the
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SQLAlchemy ORM to ignore its usage. The behavior can also be controlled on a
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per-execution basis using the ``enable_rowcount`` option with
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:meth:`_engine.Connection.execution_options`::
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conn = engine.connect().execution_options(enable_rowcount=True)
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r = conn.execute(stmt)
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print(r.rowcount)
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* ``retaining`` - False by default. Setting this to True will pass the
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``retaining=True`` keyword argument to the ``.commit()`` and ``.rollback()``
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methods of the DBAPI connection, which can improve performance in some
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situations, but apparently with significant caveats.
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Please read the fdb and/or kinterbasdb DBAPI documentation in order to
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understand the implications of this flag.
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.. versionchanged:: 0.9.0 - the ``retaining`` flag defaults to ``False``.
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In 0.8 it defaulted to ``True``.
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.. seealso::
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https://pythonhosted.org/fdb/usage-guide.html#retaining-transactions
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- information on the "retaining" flag.
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""" # noqa
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from .kinterbasdb import FBDialect_kinterbasdb
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from ... import util
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class FBDialect_fdb(FBDialect_kinterbasdb):
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supports_statement_cache = True
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def __init__(self, enable_rowcount=True, retaining=False, **kwargs):
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super(FBDialect_fdb, self).__init__(
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enable_rowcount=enable_rowcount, retaining=retaining, **kwargs
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)
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@classmethod
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def dbapi(cls):
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return __import__("fdb")
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def create_connect_args(self, url):
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opts = url.translate_connect_args(username="user")
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if opts.get("port"):
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opts["host"] = "%s/%s" % (opts["host"], opts["port"])
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del opts["port"]
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opts.update(url.query)
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util.coerce_kw_type(opts, "type_conv", int)
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return ([], opts)
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def _get_server_version_info(self, connection):
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"""Get the version of the Firebird server used by a connection.
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Returns a tuple of (`major`, `minor`, `build`), three integers
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representing the version of the attached server.
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"""
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# This is the simpler approach (the other uses the services api),
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# that for backward compatibility reasons returns a string like
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# LI-V6.3.3.12981 Firebird 2.0
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# where the first version is a fake one resembling the old
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# Interbase signature.
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isc_info_firebird_version = 103
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fbconn = connection.connection
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version = fbconn.db_info(isc_info_firebird_version)
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return self._parse_version_info(version)
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dialect = FBDialect_fdb
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