jonahgao commented on code in PR #9352:
URL: https://github.com/apache/arrow-datafusion/pull/9352#discussion_r1503695957
##########
datafusion/functions-array/src/kernels.rs:
##########
@@ -252,3 +253,67 @@ pub(super) fn array_to_string(args: &[ArrayRef]) ->
datafusion_common::Result<Ar
Ok(Arc::new(string_arr))
}
+
+use arrow::array::ListArray;
+use arrow::buffer::OffsetBuffer;
+use arrow::datatypes::Field;
+/// Generates an array of integers from start to stop with a given step.
+///
+/// This function takes 1 to 3 ArrayRefs as arguments, representing start,
stop, and step values.
+/// It returns a `Result<ArrayRef>` representing the resulting ListArray after
the operation.
+///
+/// # Arguments
+///
+/// * `args` - An array of 1 to 3 ArrayRefs representing start, stop, and
step(step value can not be zero.) values.
+///
+/// # Examples
+///
+/// gen_range(3) => [0, 1, 2]
+/// gen_range(1, 4) => [1, 2, 3]
+/// gen_range(1, 7, 2) => [1, 3, 5]
+pub fn gen_range(
+ args: &[ArrayRef],
+ include_upper: i64,
+) -> datafusion_common::Result<ArrayRef> {
+ let (start_array, stop_array, step_array) = match args.len() {
+ 1 => (None, as_int64_array(&args[0])?, None),
+ 2 => (
+ Some(as_int64_array(&args[0])?),
+ as_int64_array(&args[1])?,
+ None,
+ ),
+ 3 => (
+ Some(as_int64_array(&args[0])?),
+ as_int64_array(&args[1])?,
+ Some(as_int64_array(&args[2])?),
+ ),
+ _ => return exec_err!("gen_range expects 1 to 3 arguments"),
+ };
+
+ let mut values = vec![];
+ let mut offsets = vec![0];
+ for (idx, stop) in stop_array.iter().enumerate() {
+ let stop = stop.unwrap_or(0) + include_upper;
Review Comment:
And the result is incorrect when the step is a negative number.
```sh
DataFusion CLI v36.0.0
❯ select generate_series(5,1,-1);
+----------------------------------------------+
| generate_series(Int64(5),Int64(1),Int64(-1)) |
+----------------------------------------------+
| [5, 4, 3] |
+----------------------------------------------+
1 row in set. Query took 0.005 seconds.
```
In DuckDB:
```
D select generate_series(5,1,-1);
┌───────────────────────────┐
│ generate_series(5, 1, -1) │
│ int64[] │
├───────────────────────────┤
│ [5, 4, 3, 2, 1] │
└───────────────────────────┘
```
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