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https://issues.apache.org/jira/browse/CASSANDRA-12795?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joshua McKenzie updated CASSANDRA-12795:
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Assignee: (was: Benjamin Lerer)
> CASSANDRA-12127 changes ordering of empty buffers in reversed columns
> ---------------------------------------------------------------------
>
> Key: CASSANDRA-12795
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12795
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Tim Whittington
>
> A change to the ordering contract of empty buffers in reversed columns was
> introduced for all maintained branches (2.1.16, 2.2.8, 3.0.9, 3.8) during the
> fix for CASSANDRA-12127 by [~blerer].
> This change has wider consequences than those stated in the [comment
> introducing the
> change|https://issues.apache.org/jira/browse/CASSANDRA-12127?focusedCommentId=15368345&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15368345]
> though, and the implications aren't really called out in the release notes
> clearly, so rather than litigate it in the comments I'm creating a new issue
> to get a clear public position on the change.
> The change made was to alter the contract that the ordering of an empty byte
> buffer is always < a non empty byte buffer, in both ASC and DESC contexts -
> specifically the change introduced in 0.8 as the fix for CASSANDRA-3111 to
> make empty buffers < valued buffers in ReversedType was reverted.
> This changes the ordering of empty buffers in clustered columns with DESC
> ordering, but also in DynamicCompositeType (and CompositeType) values with
> DESC components. We have production code and data that relies on this
> behaviour, and it's not clear from the release notes whether the updates to
> scrub will also correct that data.
> So the questions I have are:
> * Was the existing behavior actually 'wrong', requiring a change? What was
> the actual (functional/specification) bug that was fixed by the change?
> * Is the new behavior the desired behavior in general? The new behavior is
> more inline with 'typical' RDMS behaviour of ordering now, but then again
> they tend to support per-query NULLS FIRST/NULLS LAST, so there's no strict
> 'right' behaviour here.
> * Did this change introduce a regression for CASSANDRA-3111?
> * Will the scrub approach fix the ordering of empty buffer values in
> DynamicCompositeType columns? If not, what do we do with production data
> created pre-2.2.8 mixed with data created with 2.2.8?
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