tohuya6 opened a new pull request, #23785:
URL: https://github.com/apache/datafusion/pull/23785
## Which issue does this PR close?
- Part of #22715.
## Rationale for this change
`multi_group_by::group_column_supported_type` gates which GROUP BY columns
may
use the column-wise `GroupValuesColumn` fast path, and the gate is
all-or-nothing: a single unsupported column forces the **entire** grouping
onto
the byte-encoded `GroupValuesRows` fallback, even when every other key column
would have qualified. A `Float16` key triggers exactly that today.
`Float16` reuses the existing `PrimitiveGroupValueBuilder` with no new
builder
type: its native `half::f16` already implements the `HashValue`
canonicalization (`hash_float!(f16, f32, f64)`), so `-0.0`/`+0.0` folding and
`NaN` grouping match `Float32`/`Float64` with no extra handling.
## What changes are included in this PR?
- Accept `Float16` in `group_column_supported_type` and dispatch it in
`make_group_column`.
- Move `Float16` from the rejected to the accepted set in the
`group_column_supported_type` ↔ `make_group_column` consistency fuzz, and
repoint the two tests that used `Float16` as their stock "unsupported"
example
to a permanently-invalid unit combo (`Time64(Second)`), so they stay
stable as
sibling primitive builders (Decimal256, Interval, …) land independently.
- Add a `(Float16, Int32)` group-count benchmark to
`benches/multi_group_by.rs`
(capped below f16's ~63.5k distinct finite values).
## Are these changes tested?
Yes.
- New unit test `test_group_values_column_float16`: a `Float16` key stays on
the
`GroupValuesColumn` path, dedups including nulls, folds `-0.0`/`+0.0` into
one
group (stored as `+0.0`), groups equal `NaN`s, and round-trips with the
`Float16` output type preserved.
- The consistency fuzz now asserts `Float16` routes through the dispatcher.
- New single- and multi-column `Float16` `GROUP BY` coverage in
`aggregate.slt`.
## Are there any user-facing changes?
No API changes. `GROUP BY` queries with a `Float16` key now use the
column-wise
fast path instead of the row-encoded fallback; results are unchanged.
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