0lai0 opened a new pull request, #3804:
URL: https://github.com/apache/datafusion-comet/pull/3804
## Which issue does this PR close?
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Closes #3125
## 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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Comet previously did not support the Spark `hours` expression (a V2
partition transform).
Queries using the `hours` function for partitioning would fall back to
Spark's JVM execution instead of running natively on DataFusion. By adding
native support for this expression, we allow more Spark workloads (especially
those partitioned by hourly intervals) to benefit from Comet's native
acceleration.
## 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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This change adds end-to-end native support for the `hours` partition
transform. Since `Hours` is a `PartitionTransformExpression` (and not a
`TimeZoneAwareExpression`), the timezone is injected from the session
configuration during the planning phase.
The native implementation uses Arrow's `unary` and `try_unary` kernels for
efficient vectorized computation, and correctly handles pre-epoch (negative)
timestamps using Euclidean floor division (`div_euclid`). It distinctly handles
both `TimestampType` (applies timezone offsets) and `TimestampNTZType` (direct
wall-clock computation).
- `expr.proto`: Added `HoursTransform` message definition to pass the child
expression and session timezone.
- `datetime.scala`: Added `CometHours` serde handler to intercept the Spark
`Hours` expression and read the timezone from `SQLConf`.
- `QueryPlanSerde.scala`: Registered the `CometHours` handler in the
temporal expressions map.
- `hours.rs`: Added `SparkHoursTransform` UDF using efficient Arrow kernels.
- `temporal.rs` & `expression_registry.rs`: Registered the native Builder
for the new expression.
## How are these changes tested?
Added comprehensive evaluation in both Rust and Scala:
1. Rust Unit Tests : Added unit tests in `hours.rs` covering:
- Positive/negative (pre-epoch) epoch handling
- Epoch boundary (zero)
- Timezone offset handling
- Null propagation
- Proper isolation of `TimestampNTZType` (ensuring it ignores timezone
offsets)
```bash
cargo test -p datafusion-comet-spark-expr -- datetime_funcs::hours
2. Scala Integration Tests: Evaluated end-to-end execution in
CometTemporalExpressionSuite.
```bash
./mvnw test -pl spark
-Dsuites='org.apache.comet.CometTemporalExpressionSuite'
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