Is there a fast way to clear Exception queue from Oracle AQ? - oracle

Question

AQ$_MESSAGES_EXCEPTIONFirst of all I know there's this question: How to clear a queue in Oracle AQ but it doesn't have an answer.
I have a lot of messages(500k) in the exception queue in the Oracle AQ(I didn't know expired messages are moved to another queue so I didn't create a consumer for those). What I need now is to be able to delete those messages fast. I've read that it's not a good idea to clear the queue table via delete, because it could lead to inconsistent state. So I've put together following procedure, but it only clears about 50 messages/second
EXECUTE dbms_aqadm.start_queue(queue_name => 'AQ$_MESSAGES_EXCEPTION',
enqueue => FALSE, dequeue => TRUE);
DECLARE
dequeue_options DBMS_AQ.dequeue_options_t;
message_properties DBMS_AQ.message_properties_t;
message_handle RAW(16);
message SYS.AQ$_JMS_MESSAGE;
no_messages EXCEPTION;
pragma exception_init (no_messages, -25228);
BEGIN
dequeue_options.wait := DBMS_AQ.NO_WAIT;
dequeue_options.navigation := DBMS_AQ.FIRST_MESSAGE;
LOOP
DBMS_AQ.DEQUEUE(
queue_name => 'AQ$_MESSAGES_EXCEPTION',
dequeue_options => dequeue_options,
message_properties => message_properties,
payload => message,
msgid => message_handle);
DBMS_OUTPUT.put_line ('Message: ' || message_handle || ' dequeued');
END LOOP;
EXCEPTION
WHEN no_messages THEN
DBMS_OUTPUT.put_line (' ---- NO MORE MESSAGES ---- ');
WHEN others then
DBMS_OUTPUT.put_line ('Exception queue not started for dequeue.');
END;
/
It seems really slow considering it's running on the database machine. This procedure takes about three hours with 500k messages. Can I do it in some more effective manner?
EDIT:
I tried the dequeue_array from the link here: http://www.oracle-developer.net/display.php?id=319
But I can't create the tables, so I'm trying to create an array to "store" the results.
Here's what I've got:
DECLARE
type messages_type is varray(500) of SYS.AQ$_JMS_MESSAGE;
messages messages_type;
dequeue_options DBMS_AQ.dequeue_options_t;
msg_properties DBMS_AQ.message_properties_array_t;
msg_ids DBMS_AQ.MSGID_ARRAY_T;
x_timeout EXCEPTION;
no_messages EXCEPTION;
dequeue_batch PLS_INTEGER := 500;
pragma exception_init (no_messages, -25228);
BEGIN
messages := messages_type();
msg_properties := DBMS_AQ.MESSAGE_PROPERTIES_ARRAY_T();
msg_properties.EXTEND(dequeue_batch);
msg_ids := DBMS_AQ.MSGID_ARRAY_T();
dequeue_options.wait := 5;
LOOP
DBMS_AQ.DEQUEUE_ARRAY(
queue_name => 'AQ$_MESSAGES_EXCEPTION',
dequeue_options => dequeue_options,
array_size => dequeue_batch,
message_properties_array => msg_properties,
payload_array => messages,
msgid_array => msg_ids);
...
I'm getting this error:
wrong number or types of arguments in call to 'DEQUEUE_ARRAY'
I think the problem is in the messages array, but I don't know what to do to make it work. Also, according to oracle doc(http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_aq.htm#i1000850), there should be another parameter:
error_array OUT error_array_t
But the explanation for this parameter is "Currently not implemented". What does it mean? Can it be left out? Should it be set to null? This is really confusing and google doesn't help here :(

Answer 1

If you really want to dequeue, you could probably use the dequeue_array(n) function. That should be much faster.
but the link you provide does have the solution :
-- purge queue
DECLARE
po_t dbms_aqadm.aq$_purge_options_t;
BEGIN
dbms_aqadm.purge_queue_table('MY_QUEUE_TABLE', NULL, po_t);
END;
Otherwise, since this exception queue is created automatically,
I guess you could just drop it, but I am not sure if that is safe
BEGIN
DBMS_AQADM.STOP_QUEUE(
queue_name => 'demo_queue'
);
DBMS_AQADM.DROP_QUEUE(
queue_name => 'demo_queue'
);
DBMS_AQADM.DROP_QUEUE_TABLE(
queue_table => 'demo_queue_table'
);
END;

Answer 2

You can use procedure "purge_queue_table" (as #Stephane said) from dbms_aqadm package but with "purge_condition" parameter specified , with this parameter you can select which messages you delete :
Example :
declare
purge_options dbms_aqadm.aq$_purge_options_t;
begin
purge_options.block := false;
purge_options.delivery_mode := dbms_aqadm.persistent;
dbms_aqadm.purge_queue_table
(queue_table => 'vista.svig_std_tab',
purge_condition => 'qtview.queue = ''AQ$_SVIG_STD_TAB_E'' and qtview.enq_time < to_date(''01.06.2014 00:00:00'',''dd.mm.yyyy hh24:mi:ss'') ',
purge_options => purge_options
);
end;
/
This example deletes messages that are from the specified exception queue and are older than the specified date. It also does this in a much quicker fashion than using "dbms_aq.dequeue" procedure.