Mithun Radhakrishnan updated HIVE-18608:
    Attachment: HIVE-18608.2-branch-2.2.patch

> ORC should allow selectively disabling dictionary-encoding on specified 
> columns
> -------------------------------------------------------------------------------
>                 Key: HIVE-18608
>                 URL: https://issues.apache.org/jira/browse/HIVE-18608
>             Project: Hive
>          Issue Type: New Feature
>          Components: ORC
>    Affects Versions: 3.0.0, 2.4.0, 2.2.1
>            Reporter: Mithun Radhakrishnan
>            Assignee: Mithun Radhakrishnan
>            Priority: Major
>         Attachments: HIVE-18608.1-branch-2.2.patch, 
> HIVE-18608.2-branch-2.2.patch
> Just as ORC allows the choice of columns to enable bloom-filters on, it would 
> be nice to have a way to specify which columns {{DICTIONARY_V2}} encoding 
> should be disabled on.
> Currently, the choice of dictionary-encoding depends on the results of 
> sampling the first row-stride within a stripe. If the user knows that a 
> column's cardinality is bound to prevent an effective dictionary, she might 
> choose to simply disable it on just that column, and avoid the cost of 
> sampling in the first row-stride.

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