This is a central requirement for hash-aggregations such as

SELECT AGG_FUNCTION(expr)
FROM table
GROUP BY expr1, expr2, ...

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

Reporter: Wes McKinney / @wesm

Related issues:

• [C++][Compute] Add scalar_hash function (is a parent of)
• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)

_{Note: This issue was originally created as ARROW-3978. Please see the migration documentation for further details.}