sjhddh opened a new pull request, #22740:
URL: https://github.com/apache/datafusion/pull/22740
## Which issue does this PR close?
- Closes #22599.
## Rationale for this change
Implements the Spark `weekday` function as part of the datafusion-spark
function library (#15914). Spark's `weekday` returns the day-of-week as a
0-indexed integer with Monday = 0 .. Sunday = 6, which differs from the
existing `dayofweek` (1-indexed, Sunday = 1). This fills a gap for
Spark-compatibility consumers.
## What changes are included in this PR?
- New `SparkWeekDay` scalar UDF in
`datafusion/spark/src/function/datetime/weekday.rs`, modeled on the sibling
`monthname` function.
- Accepts Date and (implicitly coerced) Timestamp input; returns `Int32`.
- Uses Arrow's `DatePart::DayOfWeekMonday0` kernel, which is exactly
0=Monday .. 6=Sunday — a direct match for Spark semantics.
- Null input propagates to null output for both scalar and array paths.
- Registered in the datetime function `mod.rs` (UDF macro, doc export,
`functions()` list).
## Are these changes tested?
Yes:
- Rust unit tests: return-field nullability, scalar evaluation (incl. null),
and array evaluation.
- sqllogictest coverage in
`datafusion/sqllogictest/test_files/spark/datetime/weekday.slt`: scalar dates
for all 7 weekdays, array input, TIMESTAMP / TIMESTAMP_NTZ / LTZ coercion, null
handling, and argument-type / zero-argument error cases. The original PySpark
3.5.5 reference (`weekday('2009-07-30') = 3`) is preserved and validated.
## Are there any user-facing changes?
Adds the new Spark-compatible scalar function `weekday`. No breaking changes.
---
Note: I noticed there is an existing draft PR #22601 for the same function
(last updated 2026-05-28). It appears to be a stale draft, so I've opened this
as a complete, tested implementation — happy to defer or collaborate if the
draft author is still active.
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