viirya commented on code in PR #8445:
URL: https://github.com/apache/arrow-datafusion/pull/8445#discussion_r1418478739
##########
datafusion/expr/src/window_frame.rs:
##########
@@ -142,41 +144,57 @@ impl WindowFrame {
}
}
-/// Construct equivalent explicit window frames for implicit corner cases.
-/// With this processing, we may assume in downstream code that RANGE/GROUPS
-/// frames contain an appropriate ORDER BY clause.
-pub fn regularize(mut frame: WindowFrame, order_bys: usize) ->
Result<WindowFrame> {
- if frame.units == WindowFrameUnits::Range && order_bys != 1 {
+/// Regularizes ORDER BY clause for window definition for implicit corner
cases.
+pub fn regularize_window_order_by(
+ frame: &WindowFrame,
+ order_by: &mut Vec<Expr>,
+) -> Result<()> {
+ if frame.units == WindowFrameUnits::Range && order_by.len() != 1 {
// Normally, RANGE frames require an ORDER BY clause with exactly one
// column. However, an ORDER BY clause may be absent or present but
with
// more than one column in two edge cases:
// 1. start bound is UNBOUNDED or CURRENT ROW
// 2. end bound is CURRENT ROW or UNBOUNDED.
- // In these cases, we regularize the RANGE frame to be equivalent to a
ROWS
- // frame with the UNBOUNDED bounds.
- // Note that this follows Postgres behavior.
+ // In these cases, we regularize the ORDER BY clause if the ORDER BY
clause
+ // is absent. If an ORDER BY clause is present but has more than one
column,
+ // the ORDER BY clause is unchanged. Note that this follows Postgres
behavior.
if (frame.start_bound.is_unbounded()
|| frame.start_bound == WindowFrameBound::CurrentRow)
&& (frame.end_bound == WindowFrameBound::CurrentRow
|| frame.end_bound.is_unbounded())
Review Comment:
RANGE frame with UNBOUNDED or CURRENT ROW PRECEDING/FOLLOWING without `ORDER
BY`, all rows of the partitions become peers of the current row, i.e., the
sort expression returns the same for all rows.
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