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Added documentation for the extras module.
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doc/extras.rst
133
doc/extras.rst
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@ -8,4 +8,135 @@
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This module is a generic place used to hold little helper functions and
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classes until a better place in the distribution is found.
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.. todo:: psycopg2.extras
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.. index::
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pair: Cursor; Dictionary
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.. _dict-cursor:
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Dictionary-like cursor
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----------------------
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The dict cursors allow to access to the retrieved records using an iterface
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similar to the Python dictionaries instead of the tuples. You can use it
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either passing :class:`DictConnection` as :obj:`!connection_factory` argument
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to the :func:`~psycopg2.connect` function or passing :class:`DictCursor` as
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the :class:`!cursor_factory` argument to the :meth:`~connection.cursor` method
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of a regular :class:`connection`. ::
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>>> conn = psycopg2.connect(database='test')
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>>> cur = conn.cursor(cursor_factory=psycopg2.extras.DictCursor)
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>>> cur.execute("SELECT * FROM test")
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>>> rec['id']
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1
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>>> rec['num']
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100
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>>> rec['data']
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"abc'def"
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# The records still support indexing as the original tuple
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>>> rec[2]
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"abc'def"
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.. autoclass:: DictCursor
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.. autoclass:: DictConnection
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.. autoclass:: DictRow
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Real dictionary cursor
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^^^^^^^^^^^^^^^^^^^^^^
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.. autoclass:: RealDictCursor
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.. autoclass:: RealDictConnection
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.. autoclass:: RealDictRow
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.. index::
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pair: Cursor; Logging
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Logging cursor
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--------------
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.. autoclass:: LoggingConnection
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:members: initialize,filter
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.. autoclass:: LoggingCursor
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.. autoclass:: MinTimeLoggingConnection
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:members: initialize,filter
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.. autoclass:: MinTimeLoggingCursor
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.. index::
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pair: UUID; Data types
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UUID data type
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--------------
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.. versionadded:: 2.0.9
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.. versionchanged:: 2.0.13 added UUID array support.
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::
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>>> psycopg2.extras.register_uuid()
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# Python UUID can be used in SQL queries
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>>> psycopg2.extensions.adapt(uuid.uuid4()).getquoted()
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"'1ad2b180-c17e-46ad-ad94-e1f0dfc7c34b'::uuid"
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# PostgreSQL UUID are transformed into Python UUID objects.
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>>> conn = psycopg2.connect(database='test')
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>>> cur = conn.cursor()
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>>> cur.execute("SELECT 'a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11'::uuid")
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>>> cur.fetchone()[0]
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UUID('a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11')
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.. autofunction:: register_uuid
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.. autoclass:: UUID_adapter
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.. index::
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pair: INET; Data types
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INET data type
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--------------
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::
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>>> psycopg2.extras.register_inet()
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>>> conn = psycopg2.connect(database='test')
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>>> cur = conn.cursor()
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>>> cur.execute("SELECT '192.168.0.1'::inet")
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>>> cur.fetchone()[0].addr
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'192.168.0.1'
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.. autofunction:: register_inet()
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.. autoclass:: Inet
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.. todo:: Adapter non registered: how to register it?
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.. index::
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single: Time zones; Fractional
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Fractional time zones
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---------------------
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.. versionadded:: 2.0.10
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.. autofunction:: register_tstz_w_secs
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@ -227,7 +227,9 @@ Many standards Python types are adapted into SQL and returned as Python
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objects when a query is executed.
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If you need to convert other Python types to and from PostgreSQL data types,
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see :ref:`adapting-new-types` and :ref:`type-casting-from-sql-to-python`.
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see :ref:`adapting-new-types` and :ref:`type-casting-from-sql-to-python`. You
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can also find a few other specialized adapters in the :mod:`psycopg2.extras`
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module.
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In the following examples the method :meth:`~cursor.mogrify` is used to show
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the SQL string that would be sent to the database.
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@ -97,7 +97,7 @@ class DictCursorBase(_cursor):
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return res
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class DictConnection(_connection):
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"""A connection that uses DictCursor automatically."""
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"""A connection that uses :class:`DictCursor` automatically."""
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def cursor(self, name=None):
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if name is None:
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return _connection.cursor(self, cursor_factory=DictCursor)
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@ -180,7 +180,7 @@ class DictRow(list):
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return self._index.__contains__(x)
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class RealDictConnection(_connection):
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"""A connection that uses RealDictCursor automatically."""
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"""A connection that uses :class:`RealDictCursor` automatically."""
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def cursor(self, name=None):
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if name is None:
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return _connection.cursor(self, cursor_factory=RealDictCursor)
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@ -193,7 +193,7 @@ class RealDictCursor(DictCursorBase):
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Note that this cursor is extremely specialized and does not allow
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the normal access (using integer indices) to fetched data. If you need
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to access database rows both as a dictionary and a list, then use
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the generic DictCursor instead of RealDictCursor.
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the generic :class:`DictCursor` instead of :class:`!RealDictCursor`.
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"""
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def __init__(self, *args, **kwargs):
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@ -218,6 +218,7 @@ class RealDictCursor(DictCursorBase):
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self._query_executed = 0
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class RealDictRow(dict):
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"""A ``dict`` subclass representing a data record."""
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__slots__ = ('_column_mapping')
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@ -232,13 +233,16 @@ class RealDictRow(dict):
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class LoggingConnection(_connection):
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"""A connection that logs all queries to a file or logger object."""
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"""A connection that logs all queries to a file or logger__ object.
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.. __: http://docs.python.org/library/logging.html
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"""
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def initialize(self, logobj):
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"""Initialize the connection to log to `logobj`.
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"""Initialize the connection to log to ``logobj``.
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The `logobj` parameter can be an open file object or a Logger instance
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from the standard logging module.
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The ``logobj`` parameter can be an open file object or a Logger
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instance from the standard logging module.
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"""
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self._logobj = logobj
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if logging and isinstance(logobj, logging.Logger):
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@ -294,12 +298,13 @@ class LoggingCursor(_cursor):
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class MinTimeLoggingConnection(LoggingConnection):
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"""A connection that logs queries based on execution time.
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This is just an example of how to sub-class LoggingConnection to provide
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some extra filtering for the logged queries. Both the `.inizialize()` and
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`.filter()` methods are overwritten to make sure that only queries
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executing for more than `mintime` ms are logged.
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This is just an example of how to sub-class :class:`LoggingConnection` to
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provide some extra filtering for the logged queries. Both the
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:meth:`inizialize` and :meth:`filter` methods are overwritten to make sure
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that only queries executing for more than ``mintime`` ms are logged.
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Note that this connection uses the specialized cursor MinTimeLoggingCursor.
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Note that this connection uses the specialized cursor
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:class:`MinTimeLoggingCursor`.
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"""
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def initialize(self, logobj, mintime=0):
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LoggingConnection.initialize(self, logobj)
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return _connection.cursor(self, name, cursor_factory=MinTimeLoggingCursor)
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class MinTimeLoggingCursor(LoggingCursor):
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"""The cursor sub-class companion to MinTimeLoggingConnection."""
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"""The cursor sub-class companion to :class:`MinTimeLoggingConnection`."""
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def execute(self, query, vars=None, async=0):
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self.timestamp = time.time()
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import uuid
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class UUID_adapter(object):
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"""Adapt Python's uuid.UUID type to PostgreSQL's uuid."""
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"""Adapt Python's uuid.UUID__ type to PostgreSQL's uuid__.
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.. __: http://docs.python.org/library/uuid.html
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.. __: http://www.postgresql.org/docs/8.4/static/datatype-uuid.html
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"""
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def __init__(self, uuid):
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self._uuid = uuid
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return DATETIME(s[:-3], cursor)
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def register_tstz_w_secs(oids=None, conn_or_curs=None):
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"""Register alternate type caster for TIMESTAMP WITH TIME ZONE.
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"""Register alternate type caster for :sql:`TIMESTAMP WITH TIME ZONE`.
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The Python datetime module cannot handle time zones with
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seconds in the UTC offset. There are, however, historical
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timestamp you likely want to try this type caster. It truncates
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the seconds from the time zone data and retries casting
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the timestamp. Note that this will generate timestamps
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which are INACCURATE by the number of seconds truncated
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which are **inaccurate** by the number of seconds truncated
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(unless the seconds were 00).
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<oids>
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:param oids:
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which OIDs to use this type caster for,
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defaults to TIMESTAMP WITH TIME ZONE
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<conn_or_curs>
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defaults to :sql:`TIMESTAMP WITH TIME ZONE`
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:param conn_or_curs:
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a cursor or connection if you want to attach
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this type caster to that only, defaults to
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None meaning all connections and cursors
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``None`` meaning all connections and cursors
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"""
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if oids is None:
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oids = (1184,) # hardcoded from PostgreSQL headers
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