lyne7-sc opened a new pull request, #23930:
URL: https://github.com/apache/datafusion/pull/23930
## Which issue does this PR close?
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enhancements and this helps us generate change logs for our releases. You can
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indicates that this PR will close issue #123.
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- Follow-up to #22905
- Related to #19458 and #20935
## 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.
Explaining clearly why changes are proposed helps reviewers understand your
changes and offer better suggestions for fixes.
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Previously, coercion materialized dictionary-encoded inputs for
`character_length`, `initcap`, and `reverse`. This lost the encoding and
evaluated the function for every row instead of once per dictionary value entry.
This PR extends dictionary preservation to these functions.
`character_length` and `reverse` now use `Coercible` signatures to
explicitly model string inputs and binary-to-string coercion while preserving
dictionary encoding.
## 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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- Preserve dictionary encoding for `character_length`, `initcap`, and
`reverse`.
- Evaluate only dictionary values while reusing the original keys.
- Migrate `character_length` and `reverse` from `Uniform` to `Coercible`.
- Add tests and benchmarks.
## Are these changes tested?
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Yes, covered by SQL logic tests.
## Are there any user-facing changes?
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Yes. These functions now preserve dictionary encoding in their output.
`character_length` and `reverse` now accept logical string and binary inputs
instead of implicitly converting unrelated types to strings.
## Benchmark
```
group branch
main
----- ------
----
dictionary_encoding/string/cardinality_10/character_length 1.00
218.5±32.62ns ? ?/sec 31.04 6.8±0.07µs ? ?/sec
dictionary_encoding/string/cardinality_10/initcap 1.00
292.2±4.75ns ? ?/sec 359.88 105.2±0.91µs ? ?/sec
dictionary_encoding/string/cardinality_10/reverse 1.00
501.6±15.71ns ? ?/sec 140.60 70.5±1.05µs ? ?/sec
dictionary_encoding/string/cardinality_100/character_length 1.00
307.5±24.93ns ? ?/sec 21.85 6.7±0.09µs ? ?/sec
dictionary_encoding/string/cardinality_100/initcap 1.00
1486.1±65.36ns ? ?/sec 70.56 104.9±1.57µs ? ?/sec
dictionary_encoding/string/cardinality_100/reverse 1.00
1410.9±52.69ns ? ?/sec 49.28 69.5±0.68µs ? ?/sec
dictionary_encoding/string/cardinality_1000/character_length 1.00
1007.4±93.42ns ? ?/sec 6.64 6.7±0.07µs ? ?/sec
dictionary_encoding/string/cardinality_1000/initcap 1.00
12.8±0.17µs ? ?/sec 8.41 107.5±8.55µs ? ?/sec
dictionary_encoding/string/cardinality_1000/reverse 1.00
10.5±0.24µs ? ?/sec 6.56 69.1±0.58µs ? ?/sec
dictionary_encoding/string/cardinality_8192/character_length 1.00
6.6±0.09µs ? ?/sec 1.02 6.7±0.18µs ? ?/sec
dictionary_encoding/string/cardinality_8192/initcap 1.00
104.2±1.36µs ? ?/sec 1.00 104.2±1.63µs ? ?/sec
dictionary_encoding/string/cardinality_8192/reverse 1.24
85.4±2.99µs ? ?/sec 1.00 69.0±0.58µs ? ?/sec
```
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