703 lines
25 KiB
Python
703 lines
25 KiB
Python
# postgresql/psycopg2.py
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# Copyright (C) 2005-2017 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: 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\
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[?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
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are not immediately pre-fetched and buffered after statement execution, but
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are 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 :paramref:`.Connection.execution_options.stream_results`
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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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.. seealso::
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:ref:`psycopg2_disable_native_unicode`
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* ``isolation_level``: This option, available for all PostgreSQL dialects,
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includes the ``AUTOCOMMIT`` isolation level when using the psycopg2
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dialect.
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.. seealso::
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:ref:`psycopg2_isolation_level`
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* ``client_encoding``: sets the client encoding in a libpq-agnostic way,
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using psycopg2's ``set_client_encoding()`` method.
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.. seealso::
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:ref:`psycopg2_unicode`
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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?\
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host=/var/lib/postgresql")
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See also:
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`PQconnectdbParams <http://www.postgresql.org/docs/9.1/static/\
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libpq-connect.html#LIBPQ-PQCONNECTDBPARAMS>`_
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.. _psycopg2_execution_options:
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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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* ``max_row_buffer`` - when using ``stream_results``, an integer value that
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specifies the maximum number of rows to buffer at a time. This is
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interpreted by the :class:`.BufferedRowResultProxy`, and if omitted the
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buffer will grow to ultimately store 1000 rows at a time.
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.. versionadded:: 1.0.6
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.. _psycopg2_unicode:
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Unicode with Psycopg2
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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 ``utf8``, as a more useful default::
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# postgresql.conf file
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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
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:meth:`psycopg2:connection.set_client_encoding` method
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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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# set_client_encoding() setting;
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# works for *all* PostgreSQL versions
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engine = create_engine("postgresql://user:pass@host/dbname",
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client_encoding='utf8')
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This overrides the encoding specified in the PostgreSQL client configuration.
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When using the parameter in this way, the psycopg2 driver emits
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``SET client_encoding TO 'utf8'`` on the connection explicitly, and works
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in all PostgreSQL versions.
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Note that the ``client_encoding`` setting as passed to :func:`.create_engine`
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is **not the same** as the more recently added ``client_encoding`` parameter
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now supported by libpq directly. This is enabled when ``client_encoding``
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is passed directly to ``psycopg2.connect()``, and from SQLAlchemy is passed
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using the :paramref:`.create_engine.connect_args` parameter::
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# libpq direct parameter setting;
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# only works for PostgreSQL **9.1 and above**
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engine = create_engine("postgresql://user:pass@host/dbname",
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connect_args={'client_encoding': 'utf8'})
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# using the query string is equivalent
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engine = create_engine("postgresql://user:pass@host/dbname?client_encoding=utf8")
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The above parameter was only added to libpq as of version 9.1 of PostgreSQL,
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so using the previous method is better for cross-version support.
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.. _psycopg2_disable_native_unicode:
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Disabling Native Unicode
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^^^^^^^^^^^^^^^^^^^^^^^^
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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 its 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 most DBAPIs now support unicode fully.
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Bound Parameter Styles
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----------------------
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The default parameter style for the psycopg2 dialect is "pyformat", where
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SQL is rendered using ``%(paramname)s`` style. This format has the limitation
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that it does not accommodate the unusual case of parameter names that
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actually contain percent or parenthesis symbols; as SQLAlchemy in many cases
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generates bound parameter names based on the name of a column, the presence
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of these characters in a column name can lead to problems.
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There are two solutions to the issue of a :class:`.schema.Column` that contains
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one of these characters in its name. One is to specify the
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:paramref:`.schema.Column.key` for columns that have such names::
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measurement = Table('measurement', metadata,
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Column('Size (meters)', Integer, key='size_meters')
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)
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Above, an INSERT statement such as ``measurement.insert()`` will use
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``size_meters`` as the parameter name, and a SQL expression such as
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``measurement.c.size_meters > 10`` will derive the bound parameter name
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from the ``size_meters`` key as well.
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.. versionchanged:: 1.0.0 - SQL expressions will use :attr:`.Column.key`
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as the source of naming when anonymous bound parameters are created
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in SQL expressions; previously, this behavior only applied to
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:meth:`.Table.insert` and :meth:`.Table.update` parameter names.
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The other solution is to use a positional format; psycopg2 allows use of the
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"format" paramstyle, which can be passed to
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:paramref:`.create_engine.paramstyle`::
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engine = create_engine(
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'postgresql://scott:tiger@localhost:5432/test', paramstyle='format')
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With the above engine, instead of a statement like::
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INSERT INTO measurement ("Size (meters)") VALUES (%(Size (meters))s)
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{'Size (meters)': 1}
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we instead see::
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INSERT INTO measurement ("Size (meters)") VALUES (%s)
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(1, )
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Where above, the dictionary style is converted into a tuple with positional
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style.
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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
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:meth:`.Connection.execution_options`. When using the psycopg2 dialect, these
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options make use of psycopg2's ``set_isolation_level()`` connection method,
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rather than emitting a PostgreSQL directive; this is because psycopg2's
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API-level setting is always emitted at the start of each transaction in any
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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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.. seealso::
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:ref:`postgresql_isolation_level`
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:ref:`pg8000_isolation_level`
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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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.. _psycopg2_hstore::
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HSTORE type
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------------
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The ``psycopg2`` DBAPI includes an extension to natively handle marshalling of
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the HSTORE type. The SQLAlchemy psycopg2 dialect will enable this extension
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by default when psycopg2 version 2.4 or greater is used, and
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it is detected that the target database has the HSTORE type set up for use.
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In other words, when the dialect makes the first
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connection, a sequence like the following is performed:
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1. Request the available HSTORE oids using
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``psycopg2.extras.HstoreAdapter.get_oids()``.
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If this function returns a list of HSTORE identifiers, we then determine
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that the ``HSTORE`` extension is present.
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This function is **skipped** if the version of psycopg2 installed is
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less than version 2.4.
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2. If the ``use_native_hstore`` flag is at its default of ``True``, and
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we've detected that ``HSTORE`` oids are available, the
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``psycopg2.extensions.register_hstore()`` extension is invoked for all
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connections.
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The ``register_hstore()`` extension has the effect of **all Python
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dictionaries being accepted as parameters regardless of the type of target
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column in SQL**. The dictionaries are converted by this extension into a
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textual HSTORE expression. If this behavior is not desired, disable the
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use of the hstore extension by setting ``use_native_hstore`` to ``False`` as
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follows::
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engine = create_engine("postgresql+psycopg2://scott:tiger@localhost/test",
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use_native_hstore=False)
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The ``HSTORE`` type is **still supported** when the
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``psycopg2.extensions.register_hstore()`` extension is not used. It merely
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means that the coercion between Python dictionaries and the HSTORE
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string format, on both the parameter side and the result side, will take
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place within SQLAlchemy's own marshalling logic, and not that of ``psycopg2``
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which may be more performant.
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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, _DECIMAL_TYPES, _FLOAT_TYPES,\
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_INT_TYPES, UUID
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from .hstore import HSTORE
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from .json import JSON, JSONB
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try:
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from uuid import UUID as _python_UUID
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except ImportError:
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_python_UUID = None
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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(
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decimal.Decimal,
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self._effective_decimal_return_scale)
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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 result_processor(self, dialect, coltype):
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if self.native_enum and util.py2k and self.convert_unicode is True:
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# we can't easily use PG's extensions here because
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# the OID is on the fly, and we need to give it a python
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# function anyway - not really worth it.
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self.convert_unicode = "force_nocheck"
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return super(_PGEnum, self).result_processor(dialect, coltype)
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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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class _PGJSON(JSON):
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def result_processor(self, dialect, coltype):
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if dialect._has_native_json:
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return None
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else:
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return super(_PGJSON, self).result_processor(dialect, coltype)
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class _PGJSONB(JSONB):
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def result_processor(self, dialect, coltype):
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if dialect._has_native_jsonb:
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return None
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else:
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return super(_PGJSONB, self).result_processor(dialect, coltype)
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class _PGUUID(UUID):
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def bind_processor(self, dialect):
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if not self.as_uuid and dialect.use_native_uuid:
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nonetype = type(None)
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def process(value):
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if value is not None:
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value = _python_UUID(value)
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return value
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return process
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def result_processor(self, dialect, coltype):
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if not self.as_uuid and dialect.use_native_uuid:
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def process(value):
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if value is not None:
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value = str(value)
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return value
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return process
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_server_side_id = util.counter()
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class PGExecutionContext_psycopg2(PGExecutionContext):
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def create_server_side_cursor(self):
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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:],
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hex(_server_side_id())[2:])
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return self._dbapi_connection.cursor(ident)
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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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if util.py2k:
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supports_unicode_statements = False
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supports_server_side_cursors = True
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default_paramstyle = 'pyformat'
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# set to true based on psycopg2 version
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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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FEATURE_VERSION_MAP = dict(
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native_json=(2, 5),
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native_jsonb=(2, 5, 4),
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sane_multi_rowcount=(2, 0, 9),
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array_oid=(2, 4, 3),
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hstore_adapter=(2, 4)
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)
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_has_native_hstore = False
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_has_native_json = False
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_has_native_jsonb = False
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engine_config_types = PGDialect.engine_config_types.union([
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('use_native_unicode', util.asbool),
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])
|
|
|
|
colspecs = util.update_copy(
|
|
PGDialect.colspecs,
|
|
{
|
|
sqltypes.Numeric: _PGNumeric,
|
|
ENUM: _PGEnum, # needs force_unicode
|
|
sqltypes.Enum: _PGEnum, # needs force_unicode
|
|
HSTORE: _PGHStore,
|
|
JSON: _PGJSON,
|
|
sqltypes.JSON: _PGJSON,
|
|
JSONB: _PGJSONB,
|
|
UUID: _PGUUID
|
|
}
|
|
)
|
|
|
|
def __init__(self, server_side_cursors=False, use_native_unicode=True,
|
|
client_encoding=None,
|
|
use_native_hstore=True, use_native_uuid=True,
|
|
**kwargs):
|
|
PGDialect.__init__(self, **kwargs)
|
|
self.server_side_cursors = server_side_cursors
|
|
self.use_native_unicode = use_native_unicode
|
|
self.use_native_hstore = use_native_hstore
|
|
self.use_native_uuid = use_native_uuid
|
|
self.supports_unicode_binds = use_native_unicode
|
|
self.client_encoding = client_encoding
|
|
if self.dbapi and hasattr(self.dbapi, '__version__'):
|
|
m = re.match(r'(\d+)\.(\d+)(?:\.(\d+))?',
|
|
self.dbapi.__version__)
|
|
if m:
|
|
self.psycopg2_version = tuple(
|
|
int(x)
|
|
for x in m.group(1, 2, 3)
|
|
if x is not None)
|
|
|
|
def initialize(self, connection):
|
|
super(PGDialect_psycopg2, self).initialize(connection)
|
|
self._has_native_hstore = self.use_native_hstore and \
|
|
self._hstore_oids(connection.connection) \
|
|
is not None
|
|
self._has_native_json = \
|
|
self.psycopg2_version >= self.FEATURE_VERSION_MAP['native_json']
|
|
self._has_native_jsonb = \
|
|
self.psycopg2_version >= self.FEATURE_VERSION_MAP['native_jsonb']
|
|
|
|
# http://initd.org/psycopg/docs/news.html#what-s-new-in-psycopg-2-0-9
|
|
self.supports_sane_multi_rowcount = \
|
|
self.psycopg2_version >= \
|
|
self.FEATURE_VERSION_MAP['sane_multi_rowcount']
|
|
|
|
@classmethod
|
|
def dbapi(cls):
|
|
import psycopg2
|
|
return psycopg2
|
|
|
|
@classmethod
|
|
def _psycopg2_extensions(cls):
|
|
from psycopg2 import extensions
|
|
return extensions
|
|
|
|
@classmethod
|
|
def _psycopg2_extras(cls):
|
|
from psycopg2 import extras
|
|
return extras
|
|
|
|
@util.memoized_property
|
|
def _isolation_lookup(self):
|
|
extensions = self._psycopg2_extensions()
|
|
return {
|
|
'AUTOCOMMIT': extensions.ISOLATION_LEVEL_AUTOCOMMIT,
|
|
'READ COMMITTED': extensions.ISOLATION_LEVEL_READ_COMMITTED,
|
|
'READ UNCOMMITTED': extensions.ISOLATION_LEVEL_READ_UNCOMMITTED,
|
|
'REPEATABLE READ': extensions.ISOLATION_LEVEL_REPEATABLE_READ,
|
|
'SERIALIZABLE': extensions.ISOLATION_LEVEL_SERIALIZABLE
|
|
}
|
|
|
|
def set_isolation_level(self, connection, level):
|
|
try:
|
|
level = self._isolation_lookup[level.replace('_', ' ')]
|
|
except KeyError:
|
|
raise exc.ArgumentError(
|
|
"Invalid value '%s' for isolation_level. "
|
|
"Valid isolation levels for %s are %s" %
|
|
(level, self.name, ", ".join(self._isolation_lookup))
|
|
)
|
|
|
|
connection.set_isolation_level(level)
|
|
|
|
def on_connect(self):
|
|
extras = self._psycopg2_extras()
|
|
extensions = self._psycopg2_extensions()
|
|
|
|
fns = []
|
|
if self.client_encoding is not None:
|
|
def on_connect(conn):
|
|
conn.set_client_encoding(self.client_encoding)
|
|
fns.append(on_connect)
|
|
|
|
if self.isolation_level is not None:
|
|
def on_connect(conn):
|
|
self.set_isolation_level(conn, self.isolation_level)
|
|
fns.append(on_connect)
|
|
|
|
if self.dbapi and self.use_native_uuid:
|
|
def on_connect(conn):
|
|
extras.register_uuid(None, conn)
|
|
fns.append(on_connect)
|
|
|
|
if self.dbapi and self.use_native_unicode:
|
|
def on_connect(conn):
|
|
extensions.register_type(extensions.UNICODE, conn)
|
|
extensions.register_type(extensions.UNICODEARRAY, conn)
|
|
fns.append(on_connect)
|
|
|
|
if self.dbapi and self.use_native_hstore:
|
|
def on_connect(conn):
|
|
hstore_oids = self._hstore_oids(conn)
|
|
if hstore_oids is not None:
|
|
oid, array_oid = hstore_oids
|
|
kw = {'oid': oid}
|
|
if util.py2k:
|
|
kw['unicode'] = True
|
|
if self.psycopg2_version >= \
|
|
self.FEATURE_VERSION_MAP['array_oid']:
|
|
kw['array_oid'] = array_oid
|
|
extras.register_hstore(conn, **kw)
|
|
fns.append(on_connect)
|
|
|
|
if self.dbapi and self._json_deserializer:
|
|
def on_connect(conn):
|
|
if self._has_native_json:
|
|
extras.register_default_json(
|
|
conn, loads=self._json_deserializer)
|
|
if self._has_native_jsonb:
|
|
extras.register_default_jsonb(
|
|
conn, loads=self._json_deserializer)
|
|
fns.append(on_connect)
|
|
|
|
if fns:
|
|
def on_connect(conn):
|
|
for fn in fns:
|
|
fn(conn)
|
|
return on_connect
|
|
else:
|
|
return None
|
|
|
|
@util.memoized_instancemethod
|
|
def _hstore_oids(self, conn):
|
|
if self.psycopg2_version >= self.FEATURE_VERSION_MAP['hstore_adapter']:
|
|
extras = self._psycopg2_extras()
|
|
oids = extras.HstoreAdapter.get_oids(conn)
|
|
if oids is not None and oids[0]:
|
|
return oids[0:2]
|
|
return None
|
|
|
|
def create_connect_args(self, url):
|
|
opts = url.translate_connect_args(username='user')
|
|
if 'port' in opts:
|
|
opts['port'] = int(opts['port'])
|
|
opts.update(url.query)
|
|
return ([], opts)
|
|
|
|
def is_disconnect(self, e, connection, cursor):
|
|
if isinstance(e, self.dbapi.Error):
|
|
# check the "closed" flag. this might not be
|
|
# present on old psycopg2 versions. Also,
|
|
# this flag doesn't actually help in a lot of disconnect
|
|
# situations, so don't rely on it.
|
|
if getattr(connection, 'closed', False):
|
|
return True
|
|
|
|
# checks based on strings. in the case that .closed
|
|
# didn't cut it, fall back onto these.
|
|
str_e = str(e).partition("\n")[0]
|
|
for msg in [
|
|
# these error messages from libpq: interfaces/libpq/fe-misc.c
|
|
# and interfaces/libpq/fe-secure.c.
|
|
'terminating connection',
|
|
'closed the connection',
|
|
'connection not open',
|
|
'could not receive data from server',
|
|
'could not send data to server',
|
|
# psycopg2 client errors, psycopg2/conenction.h,
|
|
# psycopg2/cursor.h
|
|
'connection already closed',
|
|
'cursor already closed',
|
|
# not sure where this path is originally from, it may
|
|
# be obsolete. It really says "losed", not "closed".
|
|
'losed the connection unexpectedly',
|
|
# these can occur in newer SSL
|
|
'connection has been closed unexpectedly',
|
|
'SSL SYSCALL error: Bad file descriptor',
|
|
'SSL SYSCALL error: EOF detected',
|
|
'SSL error: decryption failed or bad record mac',
|
|
]:
|
|
idx = str_e.find(msg)
|
|
if idx >= 0 and '"' not in str_e[:idx]:
|
|
return True
|
|
return False
|
|
|
|
dialect = PGDialect_psycopg2
|