mkaravel opened a new pull request, #58908:
URL: https://github.com/apache/spark/pull/58908
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### What changes were proposed in this pull request?
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This PR makes unary `trim`, `ltrim`, and `rtrim` use collation-aware
matching for
case-insensitive ICU collations.
The expressions now pass their collation ID to `CollationSupport`.
Interpreted execution
dispatches affected collations to the existing ICU implementation with an
ASCII-space trim
string. Code generation selects either the ICU or binary implementation
while generating code,
avoiding per-row collation dispatch in generated code.
Binary, lowercase, and case-sensitive ICU collations continue to use the
existing binary
implementation.
### Why are the changes needed?
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Unary trimming currently removes only literal ASCII space, regardless of the
input collation.
The explicit two-argument forms use ICU matching for ICU-collated operands.
As a result, the
forms disagree under case-insensitive ICU collations, where Unicode space
separators such as
NBSP compare as equivalent to ASCII space.
For example, these expressions currently produce different results:
```sql
WITH input AS (SELECT concat(chr(160), 'abc', chr(160)) AS value)
SELECT trim(value COLLATE UNICODE_CI),
trim(value COLLATE UNICODE_CI, ' ' COLLATE UNICODE_CI)
FROM input;
```
The unary form preserves both NBSP characters while the explicit form
returns `abc`. Both forms
should apply the same default trim string with the same collation semantics.
### Does this PR introduce _any_ user-facing change?
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Yes. Unary `trim`, `ltrim`, and `rtrim` now remove characters that compare
as equivalent to the
default ASCII-space trim string under case-insensitive ICU collations,
matching their explicit
two-argument forms. Behavior is unchanged for other collations.
### How was this patch tested?
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Added tests covering:
- Unary and explicit trim equivalence for every Unicode space-separator
(`Zs`) character.
- `UNICODE_CI`, `UNICODE_CI_AI`, and their `_RTRIM` variants.
- Unchanged behavior for binary, lowercase, and case-sensitive ICU
collations.
- Negative cases for tab and zero-width space.
- Interpreted and code-generated Catalyst execution.
Local execution was attempted with:
```text
build/sbt 'unsafe/testOnly
org.apache.spark.unsafe.types.CollationSupportSuite'
```
The test could not start because the environment could not resolve Maven
Central to download the
SBT launcher. The fork's Build and test and Report test results workflows
are enabled for CI
validation.
### Was this patch authored or co-authored using generative AI tooling?
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