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Add dbapi2 compatibility shim (#145)
--------- Co-authored-by: Christoph Kuhnke <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,165 @@ | ||
| """ | ||
| This module provides `PEP-249`_ DBAPI compliant connection implementation. | ||
| (see also `PEP-249-connection`_) | ||
| .. _PEP-249-connection: https://peps.python.org/pep-0249/#connection-objects | ||
| """ | ||
|
|
||
| import ssl | ||
| from functools import wraps | ||
|
|
||
| import pyexasol | ||
|
|
||
| from exasol.driver.websocket._cursor import Cursor as DefaultCursor | ||
| from exasol.driver.websocket._errors import Error | ||
|
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||
|
|
||
| def _requires_connection(method): | ||
| """ | ||
| Decorator requires the object to have a working connection. | ||
| Raises: | ||
| Error if the connection object has no active connection. | ||
| """ | ||
|
|
||
| @wraps(method) | ||
| def wrapper(self, *args, **kwargs): | ||
| if not self._connection: | ||
| raise Error("No active connection available") | ||
| return method(self, *args, **kwargs) | ||
|
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||
| return wrapper | ||
|
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|
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| class Connection: | ||
| """ | ||
| Implementation of a websocket-based connection. | ||
| For more details see :class: `Connection` protocol definition. | ||
| """ | ||
|
|
||
| def __init__( | ||
| self, | ||
| dsn: str = None, | ||
| username: str = None, | ||
| password: str = None, | ||
| schema: str = "", | ||
| autocommit: bool = True, | ||
| tls: bool = True, | ||
| certificate_validation: bool = True, | ||
| client_name: str = "EXASOL:DBAPI2:WS", | ||
| client_version: str = "unknown", | ||
| ): | ||
| """ | ||
| Create a Connection object. | ||
| Args: | ||
| dsn: Connection string, same format as for standard JDBC / ODBC drivers. | ||
| username: which will be used for the authentication. | ||
| password: which will be used for the authentication. | ||
| schema: to open after connecting. | ||
| autocommit: enable autocommit. | ||
| tls: enable tls. | ||
| certificate_validation: disable certificate validation. | ||
| client_name: which is communicated to the DB server. | ||
| """ | ||
|
|
||
| # for more details see pyexasol.connection.ExaConnection | ||
| self._options = { | ||
| "dsn": dsn, | ||
| "user": username, | ||
| "password": password, | ||
| "schema": schema, | ||
| "autocommit": autocommit, | ||
| "snapshot_transactions": None, | ||
| "connection_timeout": 10, | ||
| "socket_timeout": 30, | ||
| "query_timeout": 0, | ||
| "compression": False, | ||
| "encryption": tls, | ||
| "fetch_dict": False, | ||
| "fetch_mapper": None, | ||
| "fetch_size_bytes": 5 * 1024 * 1024, | ||
| "lower_ident": False, | ||
| "quote_ident": False, | ||
| "json_lib": "json", | ||
| "verbose_error": True, | ||
| "debug": False, | ||
| "debug_logdir": None, | ||
| "udf_output_bind_address": None, | ||
| "udf_output_connect_address": None, | ||
| "udf_output_dir": None, | ||
| "http_proxy": None, | ||
| "client_name": client_name, | ||
| "client_version": client_version, | ||
| "protocol_version": 3, | ||
| "websocket_sslopt": ( | ||
| {"cert_reqs": ssl.CERT_REQUIRED} if certificate_validation else None | ||
| ), | ||
| "access_token": None, | ||
| "refresh_token": None, | ||
| } | ||
| self._connection = None | ||
|
|
||
| def connect(self): | ||
| """See also :py:meth: `Connection.connect`""" | ||
| try: | ||
| self._connection = pyexasol.connect(**self._options) | ||
| except pyexasol.exceptions.ExaConnectionError as ex: | ||
| raise Error(f"Connection failed, {ex}") from ex | ||
| except Exception as ex: | ||
| raise Error() from ex | ||
| return self | ||
|
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||
| @property | ||
| def connection(self): | ||
| """Underlying connection used by this Connection""" | ||
| return self._connection | ||
|
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| def close(self): | ||
| """See also :py:meth: `Connection.close`""" | ||
| connection_to_close = self._connection | ||
| self._connection = None | ||
| if connection_to_close is None or connection_to_close.is_closed: | ||
| return | ||
| try: | ||
| connection_to_close.close() | ||
| except Exception as ex: | ||
| raise Error() from ex | ||
|
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||
| @_requires_connection | ||
| def commit(self): | ||
| """See also :py:meth: `Connection.commit`""" | ||
| try: | ||
| self._connection.commit() | ||
| except Exception as ex: | ||
| raise Error() from ex | ||
|
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| @_requires_connection | ||
| def rollback(self): | ||
| """See also :py:meth: `Connection.rollback`""" | ||
| try: | ||
| self._connection.rollback() | ||
| except Exception as ex: | ||
| raise Error() from ex | ||
|
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| @_requires_connection | ||
| def cursor(self): | ||
| """See also :py:meth: `Connection.cursor`""" | ||
| return DefaultCursor(self) | ||
|
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| def __del__(self): | ||
| if self._connection is None: | ||
| return | ||
|
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| # Currently, the only way to handle this gracefully is to invoke the`__del__` | ||
| # method of the underlying connection rather than calling an explicit `close`. | ||
| # | ||
| # For more details, see also: | ||
| # * https://github.com/exasol/sqlalchemy-exasol/issues/390 | ||
| # * https://github.com/exasol/pyexasol/issues/108 | ||
| # | ||
| # If the above tickets are resolved, it should be safe to switch back to using | ||
| # `close` instead of `__del__`. | ||
| self._connection.__del__() |
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