[
https://issues.apache.org/jira/browse/ARROW-12725?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
ASF GitHub Bot updated ARROW-12725:
-----------------------------------
Labels: pull-request-available (was: )
> [C++][Compute] GroupBy: improve performance by encoding keys in row format
> only when they are inserted into hash table
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: ARROW-12725
> URL: https://issues.apache.org/jira/browse/ARROW-12725
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Affects Versions: 4.0.0
> Reporter: Michal Nowakiewicz
> Priority: Major
> Labels: pull-request-available
> Fix For: 5.0.0
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Previous implementation of hash group by converts input ExecBatches to
> row-oriented format,
> then hashes and compares rows as if they were a single column.
> It is more efficient (especially for small number of key columns) to avoid
> relatively costly
> encoding and instead compute hashes of individual columns in column-oriented
> format mixing them together, and similarly comparing column-oriented data to
> row-oriented data in the hash table without converting.
> Encoding only happens for a subset of input rows that are inserted into the
> hash table - they introduce new groups.
> Keys in hash table remain stored as row-oriented.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
