sandugood commented on code in PR #22134:
URL: https://github.com/apache/datafusion/pull/22134#discussion_r3656557488
##########
datafusion/functions-window/src/lead_lag.rs:
##########
@@ -501,6 +518,89 @@ fn shift_with_default_value(
}
}
+fn shift_with_array_default(
+ array: &ArrayRef,
+ offset: i64,
+ default_values: &ArrayRef,
+) -> Result<ArrayRef> {
+ use datafusion_common::arrow::compute::concat;
+
+ let value_len = array.len() as i64;
+ if offset == 0 {
+ return Ok(Arc::clone(array));
+ }
+ if offset == i64::MIN || offset.abs() >= value_len {
+ return Ok(Arc::clone(default_values));
+ }
+
+ let slice_offset = (-offset).clamp(0, value_len) as usize;
+ let length = array.len() - offset.unsigned_abs() as usize;
+ let slice = array.slice(slice_offset, length);
+
+ let defaults_slice = if offset > 0 {
+ // Lag: defaults go at the beginning
+ default_values.slice(0, offset.unsigned_abs() as usize)
+ } else {
+ // Lead: defaults go at the end
+ let start = default_values.len() - offset.unsigned_abs() as usize;
+ default_values.slice(start, offset.unsigned_abs() as usize)
+ };
+
+ if offset > 0 {
+ concat(&[defaults_slice.as_ref(), slice.as_ref()])
+ } else {
+ concat(&[slice.as_ref(), defaults_slice.as_ref()])
+ }
+ .map_err(|e| arrow_datafusion_err!(e))
+}
+
+fn evaluate_all_with_ignore_null_and_array_default(
+ array: &ArrayRef,
+ offset: i64,
+ default_values: &ArrayRef,
+ is_lag: bool,
+) -> Result<ArrayRef> {
+ let valid_indices: Vec<usize> =
array.nulls().unwrap().valid_indices().collect();
Review Comment:
Good catch, thank you!
Added a docstring as well as the link to the arrow docs
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