Wes McKinney created ARROW-3978:
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Summary: [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
Fix For: 0.13.0
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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