[jira] [Commented] (ARROW-462) [C++] Implement in-memory conversions between non-nested primitive types and DictionaryArray equivalent

["Uwe L. Korn (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16073959#comment-16073959 ] 

Uwe L. Korn commented on ARROW-462:
-----------------------------------

PR: https://github.com/apache/arrow/pull/812

> [C++] Implement in-memory conversions between non-nested primitive types and DictionaryArray equivalent
> -------------------------------------------------------------------------------------------------------
>
>                 Key: ARROW-462
>                 URL: https://issues.apache.org/jira/browse/ARROW-462
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Wes McKinney
>            Assignee: Uwe L. Korn
>
> We use a hash table to extract unique values and dictionary indices. There may be an opportunity to consolidate common code from the dictionary encoding implementation implemented in parquet-cpp (but the dictionary indices will not be run-length encoded in Arrow):
> https://github.com/apache/parquet-cpp/blob/master/src/parquet/encodings/dictionary-encoding.h
> This functionality also needs to permit encoding split across multiple record batches -- so the hash table would be a stateful entity, and we can continue to hash more chunks of data to dictionary-encode multiple arrays with a shared dictionary at the end. 



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