lyne7-sc opened a new pull request, #24100:
URL: https://github.com/apache/datafusion/pull/24100
## Which issue does this PR close?
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- Followup to #23930
- Related to #19458 and #20935
## Rationale for this change
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Previously, coercion materialized dictionary-encoded inputs for `btrim`,
`ltrim`, and `rtrim`. 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 trim functions.
## What changes are included in this PR?
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- Preserve dictionary encoding for `btrim`, `ltrim`, and `rtrim`.
- Add tests and benchmarks.
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Yes, covered by slt
## Are there any user-facing changes?
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These functions now preserve dictionary encoding in their output.
### Benchmarks
```
group optimize
main
----- --------------
---------
dictionary_encoding/string/cardinality_10/btrim 1.00 286.8±13.36ns
? ?/sec 137.69 39.5±4.56µs ? ?/sec
dictionary_encoding/string/cardinality_10/ltrim 1.00 282.3±4.68ns
? ?/sec 151.48 42.8±8.96µs ? ?/sec
dictionary_encoding/string/cardinality_10/rtrim 1.00 278.8±13.01ns
? ?/sec 119.91 33.4±3.85µs ? ?/sec
dictionary_encoding/string/cardinality_100/btrim 1.00 718.4±4.53ns
? ?/sec 51.89 37.3±0.92µs ? ?/sec
dictionary_encoding/string/cardinality_100/ltrim 1.00 696.4±6.33ns
? ?/sec 54.02 37.6±1.68µs ? ?/sec
dictionary_encoding/string/cardinality_100/rtrim 1.00 659.2±6.91ns
? ?/sec 55.33 36.5±6.84µs ? ?/sec
dictionary_encoding/string/cardinality_1000/btrim 1.00 4.5±0.03µs
? ?/sec 9.71 43.3±8.35µs ? ?/sec
dictionary_encoding/string/cardinality_1000/ltrim 1.00 4.2±0.04µs
? ?/sec 9.06 37.8±4.46µs ? ?/sec
dictionary_encoding/string/cardinality_1000/rtrim 1.00 3.9±0.05µs
? ?/sec 8.69 33.9±1.96µs ? ?/sec
dictionary_encoding/string/cardinality_8192/btrim 1.01 37.4±1.64µs
? ?/sec 1.00 37.1±0.68µs ? ?/sec
dictionary_encoding/string/cardinality_8192/ltrim 1.00 34.7±1.75µs
? ?/sec 1.01 35.1±1.55µs ? ?/sec
dictionary_encoding/string/cardinality_8192/rtrim 1.00 31.9±1.18µs
? ?/sec 1.17 37.3±5.68µs ? ?/sec
```
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