Jonarzz opened a new issue #9382: Bound filter sorting direction URL: https://github.com/apache/druid/issues/9382 ### Motivation Changing the direction of sorting (ascending/descending) using the [bound filter](https://druid.apache.org/docs/latest/querying/filters.html#bound-filter) seems to be a natural consequence of the sorting functionality, yet it is not possible to change it. ### Proposed changes The most obvious change in the bound filter API would be the addition of a parameter. I can see two ways of implementing that: - `orderingDirection` (string), which would take one of two values: `'ascending'` and `'descending'` (`'ascending'` as default) - `ascendingOrder` (boolean), which would imply the reversed ordering (`true` as default) Obviously, documentation update is needed as well. ### Rationale The advantage of the solution described above is it's simplicity in the API and easy maintenance in the future. Yet, after vague analysis of the code, I think that it would require major changes in the code and would not be a simple functionality addition, but I might see it wrong (please, correct me if it is like so). Each comparator in [StringComparators has it's own cache ID](https://github.com/apache/druid/blob/master/processing/src/main/java/org/apache/druid/query/ordering/StringComparators.java#L46). If I understand it correctly, to handle reversed comparators correctly, the IDs for them would have to be added, so a way of distinguishing them is required. The addition of new comparators could be a simple and non-invasive change - all existing ordering options would remain unchanged and each of them would have a reversed one. Simple "reverse" flag as described above would probably be harder to implement in regard of the cache. In the API this would require expanding the `ordering` options with: `lexicographic_reversed`, `alphanumeric_reversed`, `numeric_reversed`, `strlen_reversed`, `version_reversed`. ### Operational impact - Is anything going to be deprecated or removed by this change? How will we phase out old behavior? - The default behavior for both lack of the "reverse" flag and already existing values would remain the same. - Is there a migration path that cluster operators need to be aware of? - No migration is needed. - Will there be any effect on the ability to do a rolling upgrade, or to do a rolling _downgrade_ if an operator wants to switch back to a previous version? - No.
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