FrankChen021 commented on code in PR #19301:
URL: https://github.com/apache/druid/pull/19301#discussion_r3141459735
##########
processing/src/main/java/org/apache/druid/query/operator/window/value/WindowValueProcessorBase.java:
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@@ -108,4 +112,59 @@ public List<String> getOutputColumnNames()
{
return Collections.singletonList(outputColumn);
}
+
+ /**
+ * Computes first or last value for each row respecting the given window
frame. For each row, selects
+ * either the first or last element of the frame. Entries for rows where the
frame is empty are left as null.
+ *
+ * @param first if true, selects the first element of the frame; if false,
selects the last
+ */
+ static void computeFirstOrLastValueFramed(
+ final RowsAndColumns rac,
+ final ColumnAccessor accessor,
+ final WindowFrame frame,
+ final Object[] results,
+ final boolean first
+ )
+ {
+ final int numRows = accessor.numRows();
+ final WindowFrame.Rows rowsFrame = frame.unwrap(WindowFrame.Rows.class);
+ if (rowsFrame != null) {
+ final int lower = rowsFrame.getLowerOffsetClamped(numRows);
+ final int upper = rowsFrame.getUpperOffsetClamped(numRows);
+ for (int i = 0; i < numRows; i++) {
+ final int frameLower = Math.max(0, i + lower);
+ final int frameUpper = Math.min(numRows - 1, i + upper);
+ if (frameLower <= frameUpper) {
+ results[i] = accessor.getObject(first ? frameLower : frameUpper);
+ }
+ }
+ return;
+ }
+
+ final WindowFrame.Groups groupsFrame =
frame.unwrap(WindowFrame.Groups.class);
Review Comment:
[P1] Bounded RANGE frames still execute with GROUPS semantics
The new framed path treats every non-ROWS frame as `WindowFrame.Groups`, and
`Windowing` maps Calcite's `isRows == false` windows into that representation.
That is not correct for bounded SQL RANGE frames, which must use value-distance
on the ORDER BY expression. Queries like `FIRST_VALUE(x) OVER (ORDER BY t RANGE
BETWEEN 1 PRECEDING AND CURRENT ROW)` will still return wrong answers even
though this PR now enables framed FIRST_VALUE/LAST_VALUE.
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