lyne7-sc opened a new pull request, #23549:
URL: https://github.com/apache/datafusion/pull/23549
## Which issue does this PR close?
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- Follow-up to #22905.
## Rationale for this change
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Why are you proposing this change? If this is already explained clearly in
the issue then this section is not needed.
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#22905 introduced explicit dictionary encoding preservation for coercible
function signatures, but dictionary inputs were still handled differently
across `TypeSignatureClass` variants:
| Signature category | Before | After |
| --- | --- | --- |
| `Native(...)` | Materialized by default; preserved when explicitly
requested | Same default/opt-in contract |
| Typed non-Native (e.g. `Integer`, `Numeric`, `Binary`) | Retained the
physical dictionary type by default | Materialized by default; preserved when
explicitly requested |
| `Any` | Passed through the original physical input type | Unchanged |
This PR makes the encoding preservation contract consistent across all typed
signature classes: coercion operates on the dictionary value type, and the
dictionary encoding is restored only when `EncodingPreservation::dictionary()`
is enabled.
An audit of the affected built-ins found two functions, Spark hex and
bitmap_count, that intentionally handle dictionary inputs; both now opt in
explicitly. Other affected functions generally expect materialized value
arrays, so the new default also avoids cases where signature matching accepted
a dictionary but the function implementation rejected it at execution time.
Functions that continue to materialize dictionary inputs do not gain
dictionary-aware execution efficiency yet, but they can opt in later if they
add support for encoded inputs.
## What changes are included in this PR?
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There is no need to duplicate the description in the issue here but it is
sometimes worth providing a summary of the individual changes in this PR.
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- Align dictionary coercion across typed signature classes and preserve
dictionary encoding when explicitly requested.
- Explicitly enable dictionary preservation for Spark `bitmap_count` and the
binary variant of Spark `hex`.
- Document the behavior change and migration guidance in the DataFusion
55.0.0 upgrade guide.
## Are these changes tested?
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- Unit tests cover materialization and preservation for Native, non-Native,
and `Any` inputs.
- SLTs cover `to_hex` materialization and verify that `bitmap_count`
preserves its dictionary input without an additional cast to `Binary`.
- Existing Spark `hex` dictionary tests cover its opt-in preservation
behavior.
## Are there any user-facing changes?
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updated before approving the PR.
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change` label.
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This is a behavioral API change for UDFs using typed non-Native classes such
as `Integer` or `Binary`. UDFs relying on implicit dictionary preservation must
now enable `EncodingPreservation::dictionary()` explicitly.
`TypeSignatureClass::Any` is unaffected. The upgrade guide has been updated,
and this PR should carry the `api change` label.
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