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https://issues.apache.org/jira/browse/ORC-397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16632524#comment-16632524
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Lefty Leverenz commented on ORC-397:
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Has orc.column.encoding.direct been documented in the wiki?
> ORC should allow selectively disabling dictionary-encoding on specified
> columns
> -------------------------------------------------------------------------------
>
> Key: ORC-397
> URL: https://issues.apache.org/jira/browse/ORC-397
> Project: ORC
> Issue Type: New Feature
> Reporter: Mithun Radhakrishnan
> Assignee: Mithun Radhakrishnan
> Priority: Major
> Fix For: 1.6.0, 1.5.3
>
> 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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