[jira] [Resolved] (IMPALA-5032) Consider user controls for sort materialization

["Tim Armstrong (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-5032?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-5032.
-----------------------------------
    Resolution: Later

Doesn't seem to have been a problem.

> Consider user controls for sort materialization
> -----------------------------------------------
>
>                 Key: IMPALA-5032
>                 URL: https://issues.apache.org/jira/browse/IMPALA-5032
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Clients
>    Affects Versions: Impala 2.10.0
>            Reporter: Thomas Tauber-Marshall
>            Priority: Major
>              Labels: performance
>
> A change currently being worked on (https://issues.cloudera.org/browse/IMPALA-4731) is introducing cost-based materialization of sorting exprs. This has the potential to introduce regressions if we make a bad decision, so it might be nice if the user had a way of overriding this decision.
> There are some questions to consider here:
> - Should we provide a query option, hint, or both?
> - Should a potential hint apply to the whole "order by" list or to each sort expr individually?
> - Should we allow the hint to override our decision when its either pointless (eg. forcing materialization of SlotRefs) or dangerous (eg. forcing non-materialization of potentially non-deterministic exprs)?



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