See :ref:`aqusermanual` for more information about using AQ in python-oracledb.
Note
All of these objects are extensions to the DB API.
These objects are created using the :meth:`Connection.queue()` method and are used to enqueue and dequeue messages.
.. method:: Queue.deqmany(maxMessages)
Dequeues up to the specified number of messages from the queue and returns
a list of these messages. Each element of the returned list is a
:ref:`message property<msgproperties>` object.
For consistency and compliance with the PEP 8 naming style, the name of
the method was changed from `deqMany()`. The old name will continue to
work for a period of time.
.. method:: Queue.deqone()
Dequeues at most one message from the queue. If a message is dequeued, it
will be a :ref:`message property<msgproperties>` object; otherwise, it will
be the value None.
For consistency and compliance with the PEP 8 naming style, the name of
the method was changed from `deqOne()`. The old name will continue to
work for a period of time.
.. method:: Queue.enqmany(messages)
Enqueues multiple messages into the queue. The ``messages`` parameter must be a
sequence containing :ref:`message property <msgproperties>` objects which
have all had their payload attribute set to a value that the queue
supports.
.. warning::
Calling this function in parallel on different connections
acquired from the same pool may fail due to Oracle bug 29928074. Ensure
that this function is not run in parallel, use standalone connections or
connections from different pools, or make multiple calls to
:meth:`Queue.enqone()` instead. The function :meth:`Queue.deqmany()`
call is not affected.
For consistency and compliance with the PEP 8 naming style, the name of
the method was changed from `enqMany()`. The old name will continue
to work for a period of time.
.. method:: Queue.enqone(message)
Enqueues a single message into the queue. The message must be a
:ref:`message property<msgproperties>` object which has had its payload
attribute set to a value that the queue supports.
For consistency and compliance with the PEP 8 naming style, the name of
the method was changed from `enqOne()`. The old name will continue
to work for a period of time.
.. attribute:: Queue.connection
This read-only attribute returns a reference to the connection object on
which the queue was created.
.. attribute:: Queue.deqoptions
This read-only attribute returns a reference to the :ref:`options
<deqoptions>` that will be used when dequeuing messages from the queue.
For consistency and compliance with the PEP 8 naming style, the name of
the attribute was changed from `deqOptions`. The old name will continue
to work for a period of time.
.. attribute:: Queue.enqoptions
This read-only attribute returns a reference to the :ref:`options
<enqoptions>` that will be used when enqueuing messages into the queue.
For consistency and compliance with the PEP 8 naming style, the name of
the attribute was changed from `enqOptions`. The old name will continue
to work for a period of time.
.. attribute:: Queue.name
This read-only attribute returns the name of the queue.
.. attribute:: Queue.payload_type
This read-only attribute returns the object type for payloads that can be
enqueued and dequeued. If using a JSON queue, this returns the value
``"JSON"``. If using a raw queue, this returns the value ``None``.
For consistency and compliance with the PEP 8 naming style, the name of
the attribute was changed from `payloadType`. The old name will
continue to work for a period of time.
Note
These objects are used to configure how messages are dequeued from queues. An instance of this object is found in the attribute :attr:`Queue.deqOptions`.
.. attribute:: DeqOptions.condition
This read-write attribute specifies a boolean expression similar to the where
clause of a SQL query. The boolean expression can include conditions on message
properties, user data properties and PL/SQL or SQL functions. The default
is to have no condition specified.
.. attribute:: DeqOptions.consumername
This read-write attribute specifies the name of the consumer. Only messages
matching the consumer name will be accessed. If the queue is not set up for
multiple consumers this attribute should not be set. The default is to have
no consumer name specified.
.. attribute:: DeqOptions.correlation
This read-write attribute specifies the correlation identifier of the message
to be dequeued. Special pattern-matching characters, such as the percent sign (%)
and the underscore (_), can be used. If multiple messages satisfy the
pattern, the order of dequeuing is indeterminate. The default is to have no
correlation specified.
.. attribute:: DeqOptions.deliverymode
This write-only attribute specifies what types of messages should be
dequeued. It should be one of the values :data:`~oracledb.MSG_PERSISTENT`
(default), :data:`~oracledb.MSG_BUFFERED` or
:data:`~oracledb.MSG_PERSISTENT_OR_BUFFERED`.
.. attribute:: DeqOptions.mode
This read-write attribute specifies the locking behaviour associated
with the dequeue operation. It should be one of the values
:data:`~oracledb.DEQ_BROWSE`,
:data:`~oracledb.DEQ_LOCKED`,
:data:`~oracledb.DEQ_REMOVE` (default), or
:data:`~oracledb.DEQ_REMOVE_NODATA`.
.. attribute:: DeqOptions.msgid
This read-write attribute specifies the identifier of the message to be
dequeued. The default is to have no message identifier specified.
.. attribute:: DeqOptions.navigation
This read-write attribute specifies the position of the message that
is retrieved. It should be one of the values :data:`~oracledb.DEQ_FIRST_MSG`,
:data:`~oracledb.DEQ_NEXT_MSG` (default), or
:data:`~oracledb.DEQ_NEXT_TRANSACTION`.
.. attribute:: DeqOptions.transformation
This read-write attribute specifies the name of the transformation that must
be applied after the message is dequeued from the database but before it is
returned to the calling application. The transformation must be created
using dbms_transform. The default is to have no transformation specified.
.. attribute:: DeqOptions.visibility
This read-write attribute specifies the transactional behavior of the dequeue
request. It should be one of the values :data:`~oracledb.DEQ_ON_COMMIT` (default)
or :data:`~oracledb.DEQ_IMMEDIATE`. This attribute is ignored when using
the :data:`~oracledb.DEQ_BROWSE` mode. Note the value of
:attr:`~Connection.autocommit` is always ignored.
.. attribute:: DeqOptions.wait
This read-write attribute specifies the time to wait, in seconds, for a message
matching the search criteria to become available for dequeuing. One of the
values :data:`~oracledb.DEQ_NO_WAIT` or
:data:`~oracledb.DEQ_WAIT_FOREVER` can also be used. The default is
:data:`~oracledb.DEQ_WAIT_FOREVER`.
Note
These objects are used to configure how messages are enqueued into queues. An instance of this object is found in the attribute :attr:`Queue.enqOptions`.
.. attribute:: EnqOptions.deliverymode
This write-only attribute specifies what type of messages should be
enqueued. It should be one of the values :data:`~oracledb.MSG_PERSISTENT`
(default) or :data:`~oracledb.MSG_BUFFERED`.
.. attribute:: EnqOptions.transformation
This read-write attribute specifies the name of the transformation that
must be applied before the message is enqueued into the database. The
transformation must be created using dbms_transform. The default is to have
no transformation specified.
.. attribute:: EnqOptions.visibility
This read-write attribute specifies the transactional behavior of the enqueue
request. It should be one of the values :data:`~oracledb.ENQ_ON_COMMIT` (default)
or :data:`~oracledb.ENQ_IMMEDIATE`. Note the value of
:attr:`~Connection.autocommit` is ignored.
Note
These objects are used to identify the properties of messages that are enqueued and dequeued in queues. They are created by the method :meth:`Connection.msgproperties()`. They are used by the methods :meth:`Queue.enqone()` and :meth:`Queue.enqmany()` and returned by the methods :meth:`Queue.deqone()` and :meth:`Queue.deqmany()`.
.. attribute:: MessageProperties.attempts
This read-only attribute specifies the number of attempts that have been
made to dequeue the message.
.. attribute:: MessageProperties.correlation
This read-write attribute specifies the correlation used when the message
was enqueued.
.. attribute:: MessageProperties.delay
This read-write attribute specifies the number of seconds to delay an
enqueued message. Any integer is acceptable but the constant
:data:`~oracledb.MSG_NO_DELAY` can also be used indicating that the
message is available for immediate dequeuing.
.. attribute:: MessageProperties.deliverymode
This read-only attribute specifies the type of message that was dequeued.
It will be one of the values :data:`~oracledb.MSG_PERSISTENT` or
:data:`~oracledb.MSG_BUFFERED`.
.. attribute:: MessageProperties.enqtime
This read-only attribute specifies the time that the message was enqueued.
.. attribute:: MessageProperties.exceptionq
This read-write attribute specifies the name of the queue to which the message
is moved if it cannot be processed successfully. Messages are moved if the
number of unsuccessful dequeue attempts has exceeded the maximum number of
retries or if the message has expired. All messages in the exception queue
are in the :data:`~oracledb.MSG_EXPIRED` state. The default value is the
name of the exception queue associated with the queue table.
.. attribute:: MessageProperties.expiration
This read-write attribute specifies, in seconds, how long the message is
available for dequeuing. This attribute is an offset from the delay attribute.
Expiration processing requires the queue monitor to be running. Any integer is
accepted but the constant :data:`~oracledb.MSG_NO_EXPIRATION` can also be
used indicating that the message never expires.
.. attribute:: MessageProperties.msgid
This read-only attribute specifies the id of the message in the last queue
that enqueued or dequeued the message. If the message has never been
dequeued or enqueued, the value will be `None`.
.. attribute:: MessageProperties.payload
This read-write attribute identifies the payload that will be enqueued or the
payload that was dequeued when using a :ref:`queue <queue>`. When enqueuing,
the value is checked to ensure that it conforms to the type expected by that
queue. For RAW queues, the value can be a bytes object or a string. If the
value is a string it will first be converted to bytes in the encoding UTF-8.
.. attribute:: MessageProperties.priority
This read-write attribute specifies the priority of the message. A smaller
number indicates a higher priority. The priority can be any integer, including
negative numbers. The default value is zero.
.. attribute:: MessageProperties.state
This read-only attribute specifies the state of the message at the time of
the dequeue. It will be one of the values :data:`~oracledb.MSG_WAITING`,
:data:`~oracledb.MSG_READY`, :data:`~oracledb.MSG_PROCESSED` or
:data:`~oracledb.MSG_EXPIRED`.
.. attribute:: MessageProperties.recipients
This read-write attribute specifies a list of recipient names that can be
associated with a message at the time of enqueuing the message. This allows a
limited set of recipients to dequeue each message. The recipient list associated
with the message overrides the queue subscriber list, if there is one. The
recipient names need not be in the subscriber list but can be, if desired.
To dequeue a message, the consumername attribute can be set to one of
the recipient names. The original message recipient list is not
available on dequeued messages. All recipients have to dequeue a
message before it gets removed from the queue.