Tyler Hobbs created CASSANDRA-10010:
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Summary: Paging on DISTINCT queries repeats result when first row
in partition changes
Key: CASSANDRA-10010
URL: https://issues.apache.org/jira/browse/CASSANDRA-10010
Project: Cassandra
Issue Type: Bug
Components: Core
Reporter: Tyler Hobbs
Assignee: Benjamin Lerer
Priority: Minor
Fix For: 2.1.x, 2.2.x
When paging, we always check new pages to see if they start with the same row
that the previous page ended with, and if so, we trim that row to avoid
duplicates. With {{DISTINCT}} queries, we only fetch the first row in each
partition. If that row happens to change (it's deleted, or another row is
inserted at the front of the partition) in between fetching the two pages, our
check for a matching row will fail, resulting in a duplicate row being returned.
It seems like the correct fix is to handle {{DISTINCT}} queries specially and
only check to see if the partition key matches the last returned one instead
checking that the rows match.
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