feat: implement Spark-compatible weekday function#22740
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Implements the Spark `weekday` scalar function (issue apache#22599), returning the day of the week as a 0-indexed integer where Monday = 0 .. Sunday = 6. This differs from `dayofweek` (1-indexed, Sunday = 1). The implementation is modeled on the sibling `monthname` function and uses Arrow's `DatePart::DayOfWeekMonday0` kernel, which returns 0..=6 with Monday = 0 -- an exact match for Spark semantics. It accepts Date and implicitly coerces Timestamp input, returns Int32, and propagates null input to null output. Adds Rust unit tests and sqllogictest coverage for scalar/array/timestamp/ null/error cases. Closes apache#22599 Signed-off-by: sjhddh <151469562+sjhddh@users.noreply.github.com>
Jefffrey
approved these changes
Jun 4, 2026
| signature: Signature::coercible( | ||
| vec![Coercion::new_implicit( | ||
| TypeSignatureClass::Native(logical_date()), | ||
| vec![TypeSignatureClass::Timestamp], |
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i think we need to accept coercion from string too?
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Which issue does this PR close?
weekday#22599.Rationale for this change
Implements the Spark
weekdayfunction as part of the datafusion-spark function library (#15914). Spark'sweekdayreturns the day-of-week as a 0-indexed integer with Monday = 0 .. Sunday = 6, which differs from the existingdayofweek(1-indexed, Sunday = 1). This fills a gap for Spark-compatibility consumers.What changes are included in this PR?
SparkWeekDayscalar UDF indatafusion/spark/src/function/datetime/weekday.rs, modeled on the siblingmonthnamefunction.Int32.DatePart::DayOfWeekMonday0kernel, which is exactly 0=Monday .. 6=Sunday — a direct match for Spark semantics.mod.rs(UDF macro, doc export,functions()list).Are these changes tested?
Yes:
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.