lyne7-sc opened a new pull request, #23743:
URL: https://github.com/apache/datafusion/pull/23743
## Which issue does this PR close?
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- Follow-up to #22905
- Related to #19458
- Related to #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.
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String functions normally materialize `Dictionary(K, Utf8)` inputs before
evaluation. This loses the dictionary encoding and applies the function to
every row instead of only the unique dictionary values.
This pr extends the dictionary-preserving implementation from #22905 to
`ascii`, `bit_length`, and `octet_length`.
## 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 `ascii`, `bit_length`, and `octet_length`.
- Preserve return types for regular and nested dictionaries.
- Add slts and Dictionary cardinality benchmarks.
## Are these changes tested?
Yes, covered by SLTs.
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## Are there any user-facing changes?
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Yes. These functions now preserve Dictionary encoding in their output:
`Dictionary(K, Utf8) -> Dictionary(K, Int32)`
## Benchmarks
```
group main
new
-----
---------------- ---
dictionary_string_functions/cardinality_10/ascii 28.71
5.0±0.05µs ? ?/sec 1.00 172.5±12.31ns ? ?/sec
dictionary_string_functions/cardinality_10/bit_length 4.01
698.7±25.75ns ? ?/sec 1.00 174.1±2.45ns ? ?/sec
dictionary_string_functions/cardinality_10/octet_length 3.63
651.3±58.51ns ? ?/sec 1.00 179.4±3.27ns ? ?/sec
dictionary_string_functions/cardinality_100/ascii 18.92
4.9±0.03µs ? ?/sec 1.00 258.6±8.28ns ? ?/sec
dictionary_string_functions/cardinality_100/bit_length 3.11
723.4±27.14ns ? ?/sec 1.00 232.5±35.47ns ? ?/sec
dictionary_string_functions/cardinality_100/octet_length 3.06
651.6±26.97ns ? ?/sec 1.00 213.2±6.96ns ? ?/sec
dictionary_string_functions/cardinality_1000/ascii 6.32
4.8±0.03µs ? ?/sec 1.00 766.7±70.66ns ? ?/sec
dictionary_string_functions/cardinality_1000/bit_length 3.06
776.1±67.85ns ? ?/sec 1.00 253.9±6.93ns ? ?/sec
dictionary_string_functions/cardinality_1000/octet_length 3.10
807.9±188.65ns ? ?/sec 1.00 261.0±22.42ns ? ?/sec
dictionary_string_functions/cardinality_8192/ascii 1.00
5.1±0.15µs ? ?/sec 1.00 5.1±0.24µs ? ?/sec
dictionary_string_functions/cardinality_8192/bit_length 1.00
699.1±17.54ns ? ?/sec 1.09 763.7±36.57ns ? ?/sec
dictionary_string_functions/cardinality_8192/octet_length 1.00
677.3±62.91ns ? ?/sec 1.11 750.7±32.56ns ? ?/sec
```
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