475 lines
18 KiB
Python
475 lines
18 KiB
Python
# postgresql/psycopg2.py
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# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <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: http://www.opensource.org/licenses/mit-license.php
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"""
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.. dialect:: postgresql+psycopg2
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:name: psycopg2
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:dbapi: psycopg2
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:connectstring: postgresql+psycopg2://user:password@host:port/dbname[?key=value&key=value...]
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:url: http://pypi.python.org/pypi/psycopg2/
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psycopg2 Connect Arguments
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-----------------------------------
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psycopg2-specific keyword arguments which are accepted by
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:func:`.create_engine()` are:
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* ``server_side_cursors``: Enable the usage of "server side cursors" for SQL
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statements which support this feature. What this essentially means from a
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psycopg2 point of view is that the cursor is created using a name, e.g.
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``connection.cursor('some name')``, which has the effect that result rows are
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not immediately pre-fetched and buffered after statement execution, but are
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instead left on the server and only retrieved as needed. SQLAlchemy's
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:class:`~sqlalchemy.engine.ResultProxy` uses special row-buffering
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behavior when this feature is enabled, such that groups of 100 rows at a
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time are fetched over the wire to reduce conversational overhead.
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Note that the ``stream_results=True`` execution option is a more targeted
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way of enabling this mode on a per-execution basis.
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* ``use_native_unicode``: Enable the usage of Psycopg2 "native unicode" mode
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per connection. True by default.
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* ``isolation_level``: This option, available for all Posgtresql dialects,
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includes the ``AUTOCOMMIT`` isolation level when using the psycopg2
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dialect. See :ref:`psycopg2_isolation_level`.
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Unix Domain Connections
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------------------------
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psycopg2 supports connecting via Unix domain connections. When the ``host``
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portion of the URL is omitted, SQLAlchemy passes ``None`` to psycopg2,
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which specifies Unix-domain communication rather than TCP/IP communication::
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create_engine("postgresql+psycopg2://user:password@/dbname")
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By default, the socket file used is to connect to a Unix-domain socket
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in ``/tmp``, or whatever socket directory was specified when PostgreSQL
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was built. This value can be overridden by passing a pathname to psycopg2,
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using ``host`` as an additional keyword argument::
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create_engine("postgresql+psycopg2://user:password@/dbname?host=/var/lib/postgresql")
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See also:
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`PQconnectdbParams <http://www.postgresql.org/docs/9.1/static/libpq-connect.html#LIBPQ-PQCONNECTDBPARAMS>`_
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Per-Statement/Connection Execution Options
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-------------------------------------------
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The following DBAPI-specific options are respected when used with
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:meth:`.Connection.execution_options`, :meth:`.Executable.execution_options`,
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:meth:`.Query.execution_options`, in addition to those not specific to DBAPIs:
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* isolation_level - Set the transaction isolation level for the lifespan of a
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:class:`.Connection` (can only be set on a connection, not a statement
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or query). See :ref:`psycopg2_isolation_level`.
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* stream_results - Enable or disable usage of psycopg2 server side cursors -
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this feature makes use of "named" cursors in combination with special
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result handling methods so that result rows are not fully buffered.
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If ``None`` or not set, the ``server_side_cursors`` option of the
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:class:`.Engine` is used.
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Unicode
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-------
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By default, the psycopg2 driver uses the ``psycopg2.extensions.UNICODE``
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extension, such that the DBAPI receives and returns all strings as Python
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Unicode objects directly - SQLAlchemy passes these values through without
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change. Psycopg2 here will encode/decode string values based on the
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current "client encoding" setting; by default this is the value in
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the ``postgresql.conf`` file, which often defaults to ``SQL_ASCII``.
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Typically, this can be changed to ``utf-8``, as a more useful default::
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#client_encoding = sql_ascii # actually, defaults to database
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# encoding
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client_encoding = utf8
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A second way to affect the client encoding is to set it within Psycopg2
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locally. SQLAlchemy will call psycopg2's ``set_client_encoding()``
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method (see: http://initd.org/psycopg/docs/connection.html#connection.set_client_encoding)
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on all new connections based on the value passed to
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:func:`.create_engine` using the ``client_encoding`` parameter::
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engine = create_engine("postgresql://user:pass@host/dbname", client_encoding='utf8')
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This overrides the encoding specified in the Postgresql client configuration.
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.. versionadded:: 0.7.3
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The psycopg2-specific ``client_encoding`` parameter to
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:func:`.create_engine`.
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SQLAlchemy can also be instructed to skip the usage of the psycopg2
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``UNICODE`` extension and to instead utilize it's own unicode encode/decode
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services, which are normally reserved only for those DBAPIs that don't
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fully support unicode directly. Passing ``use_native_unicode=False`` to
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:func:`.create_engine` will disable usage of ``psycopg2.extensions.UNICODE``.
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SQLAlchemy will instead encode data itself into Python bytestrings on the way
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in and coerce from bytes on the way back,
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using the value of the :func:`.create_engine` ``encoding`` parameter, which
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defaults to ``utf-8``.
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SQLAlchemy's own unicode encode/decode functionality is steadily becoming
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obsolete as more DBAPIs support unicode fully along with the approach of
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Python 3; in modern usage psycopg2 should be relied upon to handle unicode.
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Transactions
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------------
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The psycopg2 dialect fully supports SAVEPOINT and two-phase commit operations.
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.. _psycopg2_isolation_level:
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Psycopg2 Transaction Isolation Level
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-------------------------------------
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As discussed in :ref:`postgresql_isolation_level`,
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all Postgresql dialects support setting of transaction isolation level
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both via the ``isolation_level`` parameter passed to :func:`.create_engine`,
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as well as the ``isolation_level`` argument used by :meth:`.Connection.execution_options`.
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When using the psycopg2 dialect, these options make use of
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psycopg2's ``set_isolation_level()`` connection method, rather than
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emitting a Postgresql directive; this is because psycopg2's API-level
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setting is always emitted at the start of each transaction in any case.
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The psycopg2 dialect supports these constants for isolation level:
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* ``READ COMMITTED``
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* ``READ UNCOMMITTED``
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* ``REPEATABLE READ``
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* ``SERIALIZABLE``
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* ``AUTOCOMMIT``
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.. versionadded:: 0.8.2 support for AUTOCOMMIT isolation level when using
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psycopg2.
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NOTICE logging
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---------------
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The psycopg2 dialect will log Postgresql NOTICE messages via the
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``sqlalchemy.dialects.postgresql`` logger::
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import logging
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logging.getLogger('sqlalchemy.dialects.postgresql').setLevel(logging.INFO)
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HSTORE type
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------------
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The psycopg2 dialect will make use of the
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``psycopg2.extensions.register_hstore()`` extension when using the HSTORE
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type. This replaces SQLAlchemy's pure-Python HSTORE coercion which takes
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effect for other DBAPIs.
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"""
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from __future__ import absolute_import
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import re
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import logging
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from ... import util, exc
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import decimal
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from ... import processors
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from ...engine import result as _result
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from ...sql import expression
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from ... import types as sqltypes
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from .base import PGDialect, PGCompiler, \
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PGIdentifierPreparer, PGExecutionContext, \
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ENUM, ARRAY, _DECIMAL_TYPES, _FLOAT_TYPES,\
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_INT_TYPES
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from .hstore import HSTORE
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logger = logging.getLogger('sqlalchemy.dialects.postgresql')
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class _PGNumeric(sqltypes.Numeric):
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def bind_processor(self, dialect):
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return None
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def result_processor(self, dialect, coltype):
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if self.asdecimal:
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if coltype in _FLOAT_TYPES:
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return processors.to_decimal_processor_factory(decimal.Decimal)
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elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
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# pg8000 returns Decimal natively for 1700
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return None
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else:
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raise exc.InvalidRequestError(
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"Unknown PG numeric type: %d" % coltype)
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else:
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if coltype in _FLOAT_TYPES:
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# pg8000 returns float natively for 701
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return None
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elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
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return processors.to_float
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else:
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raise exc.InvalidRequestError(
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"Unknown PG numeric type: %d" % coltype)
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class _PGEnum(ENUM):
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def __init__(self, *arg, **kw):
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super(_PGEnum, self).__init__(*arg, **kw)
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# Py2K
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if self.convert_unicode:
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self.convert_unicode = "force"
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# end Py2K
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class _PGArray(ARRAY):
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def __init__(self, *arg, **kw):
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super(_PGArray, self).__init__(*arg, **kw)
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# Py2K
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# FIXME: this check won't work for setups that
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# have convert_unicode only on their create_engine().
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if isinstance(self.item_type, sqltypes.String) and \
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self.item_type.convert_unicode:
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self.item_type.convert_unicode = "force"
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# end Py2K
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class _PGHStore(HSTORE):
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def bind_processor(self, dialect):
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if dialect._has_native_hstore:
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return None
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else:
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return super(_PGHStore, self).bind_processor(dialect)
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def result_processor(self, dialect, coltype):
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if dialect._has_native_hstore:
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return None
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else:
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return super(_PGHStore, self).result_processor(dialect, coltype)
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# When we're handed literal SQL, ensure it's a SELECT-query. Since
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# 8.3, combining cursors and "FOR UPDATE" has been fine.
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SERVER_SIDE_CURSOR_RE = re.compile(
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r'\s*SELECT',
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re.I | re.UNICODE)
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_server_side_id = util.counter()
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class PGExecutionContext_psycopg2(PGExecutionContext):
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def create_cursor(self):
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# TODO: coverage for server side cursors + select.for_update()
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if self.dialect.server_side_cursors:
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is_server_side = \
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self.execution_options.get('stream_results', True) and (
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(self.compiled and isinstance(self.compiled.statement, expression.Selectable) \
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or \
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(
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(not self.compiled or
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isinstance(self.compiled.statement, expression.TextClause))
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and self.statement and SERVER_SIDE_CURSOR_RE.match(self.statement))
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)
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)
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else:
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is_server_side = \
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self.execution_options.get('stream_results', False)
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self.__is_server_side = is_server_side
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if is_server_side:
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# use server-side cursors:
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# http://lists.initd.org/pipermail/psycopg/2007-January/005251.html
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ident = "c_%s_%s" % (hex(id(self))[2:], hex(_server_side_id())[2:])
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return self._dbapi_connection.cursor(ident)
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else:
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return self._dbapi_connection.cursor()
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def get_result_proxy(self):
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# TODO: ouch
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if logger.isEnabledFor(logging.INFO):
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self._log_notices(self.cursor)
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if self.__is_server_side:
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return _result.BufferedRowResultProxy(self)
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else:
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return _result.ResultProxy(self)
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def _log_notices(self, cursor):
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for notice in cursor.connection.notices:
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# NOTICE messages have a
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# newline character at the end
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logger.info(notice.rstrip())
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cursor.connection.notices[:] = []
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class PGCompiler_psycopg2(PGCompiler):
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def visit_mod_binary(self, binary, operator, **kw):
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return self.process(binary.left, **kw) + " %% " + \
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self.process(binary.right, **kw)
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def post_process_text(self, text):
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return text.replace('%', '%%')
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class PGIdentifierPreparer_psycopg2(PGIdentifierPreparer):
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def _escape_identifier(self, value):
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value = value.replace(self.escape_quote, self.escape_to_quote)
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return value.replace('%', '%%')
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class PGDialect_psycopg2(PGDialect):
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driver = 'psycopg2'
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# Py2K
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supports_unicode_statements = False
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# end Py2K
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default_paramstyle = 'pyformat'
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supports_sane_multi_rowcount = False
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execution_ctx_cls = PGExecutionContext_psycopg2
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statement_compiler = PGCompiler_psycopg2
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preparer = PGIdentifierPreparer_psycopg2
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psycopg2_version = (0, 0)
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_has_native_hstore = False
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colspecs = util.update_copy(
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PGDialect.colspecs,
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{
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sqltypes.Numeric: _PGNumeric,
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ENUM: _PGEnum, # needs force_unicode
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sqltypes.Enum: _PGEnum, # needs force_unicode
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ARRAY: _PGArray, # needs force_unicode
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HSTORE: _PGHStore,
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}
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)
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def __init__(self, server_side_cursors=False, use_native_unicode=True,
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client_encoding=None,
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use_native_hstore=True,
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**kwargs):
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PGDialect.__init__(self, **kwargs)
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self.server_side_cursors = server_side_cursors
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self.use_native_unicode = use_native_unicode
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self.use_native_hstore = use_native_hstore
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self.supports_unicode_binds = use_native_unicode
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self.client_encoding = client_encoding
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if self.dbapi and hasattr(self.dbapi, '__version__'):
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m = re.match(r'(\d+)\.(\d+)(?:\.(\d+))?',
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self.dbapi.__version__)
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if m:
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self.psycopg2_version = tuple(
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int(x)
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for x in m.group(1, 2, 3)
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if x is not None)
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def initialize(self, connection):
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super(PGDialect_psycopg2, self).initialize(connection)
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self._has_native_hstore = self.use_native_hstore and \
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self._hstore_oids(connection.connection) \
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is not None
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@classmethod
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def dbapi(cls):
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import psycopg2
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return psycopg2
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@util.memoized_property
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def _isolation_lookup(self):
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extensions = __import__('psycopg2.extensions').extensions
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return {
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'AUTOCOMMIT': extensions.ISOLATION_LEVEL_AUTOCOMMIT,
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'READ COMMITTED': extensions.ISOLATION_LEVEL_READ_COMMITTED,
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'READ UNCOMMITTED': extensions.ISOLATION_LEVEL_READ_UNCOMMITTED,
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'REPEATABLE READ': extensions.ISOLATION_LEVEL_REPEATABLE_READ,
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'SERIALIZABLE': extensions.ISOLATION_LEVEL_SERIALIZABLE
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}
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def set_isolation_level(self, connection, level):
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try:
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level = self._isolation_lookup[level.replace('_', ' ')]
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except KeyError:
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raise exc.ArgumentError(
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"Invalid value '%s' for isolation_level. "
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"Valid isolation levels for %s are %s" %
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(level, self.name, ", ".join(self._isolation_lookup))
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)
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connection.set_isolation_level(level)
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def on_connect(self):
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from psycopg2 import extras, extensions
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fns = []
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if self.client_encoding is not None:
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def on_connect(conn):
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conn.set_client_encoding(self.client_encoding)
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fns.append(on_connect)
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if self.isolation_level is not None:
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def on_connect(conn):
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self.set_isolation_level(conn, self.isolation_level)
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fns.append(on_connect)
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if self.dbapi and self.use_native_unicode:
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def on_connect(conn):
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extensions.register_type(extensions.UNICODE, conn)
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fns.append(on_connect)
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if self.dbapi and self.use_native_hstore:
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def on_connect(conn):
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hstore_oids = self._hstore_oids(conn)
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if hstore_oids is not None:
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oid, array_oid = hstore_oids
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if util.py2k:
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extras.register_hstore(conn, oid=oid,
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array_oid=array_oid,
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unicode=True)
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else:
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extras.register_hstore(conn, oid=oid,
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array_oid=array_oid)
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fns.append(on_connect)
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if fns:
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def on_connect(conn):
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for fn in fns:
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fn(conn)
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return on_connect
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else:
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return None
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@util.memoized_instancemethod
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def _hstore_oids(self, conn):
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if self.psycopg2_version >= (2, 4):
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from psycopg2 import extras
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oids = extras.HstoreAdapter.get_oids(conn)
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if oids is not None and oids[0]:
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return oids[0:2]
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return None
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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 'port' in opts:
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opts['port'] = int(opts['port'])
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opts.update(url.query)
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return ([], opts)
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def is_disconnect(self, e, connection, cursor):
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if isinstance(e, self.dbapi.Error):
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str_e = str(e).partition("\n")[0]
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for msg in [
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# these error messages from libpq: interfaces/libpq/fe-misc.c
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# and interfaces/libpq/fe-secure.c.
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# TODO: these are sent through gettext in libpq and we can't
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# check within other locales - consider using connection.closed
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'terminating connection',
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'closed the connection',
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'connection not open',
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'could not receive data from server',
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# psycopg2 client errors, psycopg2/conenction.h, psycopg2/cursor.h
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'connection already closed',
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'cursor already closed',
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# not sure where this path is originally from, it may
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# be obsolete. It really says "losed", not "closed".
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'losed the connection unexpectedly'
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]:
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idx = str_e.find(msg)
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if idx >= 0 and '"' not in str_e[:idx]:
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return True
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return False
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dialect = PGDialect_psycopg2
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