aloyszhang opened a new pull request, #19581:
URL: https://github.com/apache/pulsar/pull/19581

   
   ### Motivation
   
   There're some cases of consumers receiving duplicated messages when there 
are ongoing transactions within a subscription.
   #14327  has fixed this problem partially. But there's still a chance for 
consumers to receive duplicated messages.
   
   1. For non-batch messages, the dispatcher does not filter messages in the 
pendingAck state(PendingAckHandleImpl#individualAckPositions)
   
   2. For batch messages,  if the ackSet in pendingAck state is complimentary 
with the ackSet in the cursor(the result of the two ackSet AND is empty), the 
broker still dispatches this entry to the consumer.  For example, a batch 
message has 5 messages internal.
   - cursor stats has acked 0,1,2
   - pendingAck stats has acked 3,4
   This message should not dispatch to the consumer.
   
   ### Modifications
   
   1. filter messages in pendingAck for non-batch messages
   2. filter messages ackSet in pendingAck state is complimentary with the 
ackSet in the cursor for batch messages
   
   ### Verifying this change
   
   - [ ] Make sure that the change passes the CI checks.
   
   
   ### Documentation
   
   - [ ] `doc-not-needed` <!-- Your PR changes do not impact docs -->
   
   
   ### Matching PR in forked repository
   
   PR in forked repository: <!-- ENTER URL HERE -->
   
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