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https://issues.apache.org/jira/browse/ARROW-3978?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17574066#comment-17574066
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Aldrin Montana commented on ARROW-3978:
---------------------------------------
I just wanted to note here that I am trying to handle nested types for
ARROW-8991. I realize now that StructArray would be included in that umbrella,
so when ARROW-8991 is complete, this would be partially completed.
I don't know the dictionary-encoding infrastructure, but if I get around to
that half then I'll pick up this issue.
> [C++] Implement hashing, dictionary-encoding for StructArray
> ------------------------------------------------------------
>
> Key: ARROW-3978
> URL: https://issues.apache.org/jira/browse/ARROW-3978
> Project: Apache Arrow
> Issue Type: New Feature
> Components: C++
> Reporter: Wes McKinney
> Priority: Major
> Labels: query-engine
>
> This is a central requirement for hash-aggregations such as
> {code}
> SELECT AGG_FUNCTION(expr)
> FROM table
> GROUP BY expr1, expr2, ...
> {code}
> The materialized keys in the GROUP BY section form a struct, which can be
> incrementally hashed to produce dictionary codes suitable for computing
> aggregates or any other purpose.
> There are a few subtasks related to this, such as efficiently constructing a
> record (that can be hashed quickly) to identify each "row" in the struct.
> Maybe we should start with that first
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