The AMQP WG discussed this yesterday.
The working group is likely to select a proposal into 0-9 for selectors.
Note that the 0-9 will provide facilities to pass the necessary parameters
in the protocol, BUT it will say nothing about the selector language. That
will come later, in 0-10 (yes, complain now about our perverse numbering
scheme :-). There is no guarantee of which selector language will be
chosen, but some SQL92 variant has got to have a fighting chance.
John
On 29/11/06, Martin Ritchie (JIRA) <[email protected]> wrote:
[
http://issues.apache.org/jira/browse/QPID-21?page=comments#action_12454302]
Martin Ritchie commented on QPID-21:
------------------------------------
Implementation of selectors is not possible with AMQP 0.8 as there is no
way to convey the selector string to the broker. Request to AMQP WG has been
made to address this.
> Add JMS Message Selector Capability
> -----------------------------------
>
> Key: QPID-21
> URL: http://issues.apache.org/jira/browse/QPID-21
> Project: Qpid
> Issue Type: New Feature
> Components: Java Broker, Java Client
> Reporter: Marnie McCormack
> Assigned To: Martin Ritchie
> Fix For: M2
>
>
> Raised this JIRA to document a known gap (required for JMS compliance)
and in response to an end user request. This task may have implications for
the AMQP protocol and some investigation is required on this point before
completing implementation work.
> Info below quoted from JMS Specification, section 3.8 (see specification
for full details of JMS selector syntax & refs used below):
> A JMS message selector allows a client to specify, by message header,
the messages it's interested in. Only messages whose headers and properties
match the selector are delivered. The semantics of not delivered differ a
bit depending on the MessageConsumer being used. See Section
5.8,"QueueReceiver,"
and Section 6.11, "TopicSubscriber," for more details.
> Message selectors cannot reference message body values. A message
selector matches a message if the selector evaluates to true when
> the message's header field and property values are substituted for their
corresponding identifiers in the selector.
> This additional information from the SUN JMS guide:
> A message selector is a String that contains an expression. The syntax
of the expression is based on a subset of the SQL92 conditional expression
syntax. The message selector in the example selects any message that has a
NewsType property that is set to the value 'Sports' or 'Opinion':
> NewsType = 'Sports' OR NewsType = 'Opinion'
> The createConsumer and createDurableSubscriber methods allow you to
specify a message selector as an argument when you create a message
consumer.
> The message consumer then receives only messages whose headers and
properties match the selector. (See Message Headers, and Message
Properties.) A message selector cannot select messages on the basis of the
content of the message body.
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