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https://issues.apache.org/jira/browse/CASSANDRA-12872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16166781#comment-16166781
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Benedict commented on CASSANDRA-12872:
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nit: the comment suggests we will not apply the transformations "correctly" to
future partitions; in reality, the new transformation will be applied just
fine, we will just begin accumulating the old ones. Since it was the counter
transformation preceding MoreRows, this meant we began double, triple, etc.
counting each time we extended. Had it been the "protection" transformation
this would have just meant a transient memory leak (of sorts) and a modest
incremental CPU burden.
Also, grammatically, we're not "extending MoreRows" we're extending "partition"
_with_ MoreRows ;)
+1
> Paging reads and limit reads are missing some data
> --------------------------------------------------
>
> Key: CASSANDRA-12872
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12872
> Project: Cassandra
> Issue Type: Bug
> Components: Coordination
> Reporter: Bhaskar Muppana
> Assignee: Aleksey Yeschenko
> Priority: Critical
> Labels: Correctness
> Fix For: 3.0.x, 3.11.x, 4.x
>
> Attachments: limiterr-reproduce.sh
>
>
> We are seeing an issue with paging reads missing some small number of columns
> when we do paging/limit reads. We get this on a single DC cluster itself when
> both reads and writes are happening with QUORUM. Paging/limit reads see this
> issue. I have attached the ccm based script which reproduces the problem.
> * Keyspace RF - 3
> * Table (id int, course text, marks int, primary key(id, course))
> * replicas for partition key 1 - r1, r2 and r3
> * insert (1, '1', 1) , (1, '2', 2), (1, '3', 3), (1, '4', 4), (1, '5', 5)
> - succeeded on all 3 replicas
> * insert (1, '6', 6) succeeded on r1 and r3, failed on r2
> * delete (1, '2'), (1, '3'), (1, '4'), (1, '5') succeeded on r1 and r2,
> failed on r3
> * insert (1, '7', 7) succeeded on r1 and r2, failed on r3
> Local data on 3 nodes looks like as below now
> r1: (1, '1', 1), tombstone(2-5 records), (1, '6', 6), (1, '7', 7)
> r2: (1, '1', 1), tombstone(2-5 records), (1, '7', 7)
> r3: (1, '1', 1), (1, '2', 2), (1, '3', 3), (1, '4', 4), (1, '5', 5), (1,
> '6', 6)
> If we do a paging read with page_size 2, and if it gets data from r2 and r3,
> then it will only get the data (1, '1', 1) and (1, '7', 7) skipping record 6.
> This problem would happen if the same query is not doing paging but limit set
> to 2 records.
> Resolution code for reads works same for paging queries and normal queries.
> Co-ordinator shouldn't respond back to client with records/columns that it
> didn't have complete visibility on all required replicas (in this case 2
> replicas). In above case, it is sending back record (1, '7', 7) back to
> client, but its visibility on r3 is limited up to (1, '2', 2) and it is
> relying on just r2 data to assume (1, '6', 6) doesn't exist, which is wrong.
> End of the resolution all it can conclusively say any thing about is (1, '1',
> and the other one is that we and and and and and and the and the and the
> and d and the other is and 1), which exists and (1, '2', 2), which is deleted.
> Ideally we should have different resolution implementation for paging/limit
> queries.
> We could reproduce this on 2.0.17, 2.1.16 and 3.0.9.
> Seems like 3.0.9 we have ShortReadProtection transformation on list queries.
> I assume that is to protect against the cases like above. But, we can
> reproduce the issue in 3.0.9 as well.
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