beliefer commented on a change in pull request #27440: [SPARK-27951][SQL]
Support ANSI SQL NTH_VALUE window function
URL: https://github.com/apache/spark/pull/27440#discussion_r376889490
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/window/WindowFunctionFrame.scala
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@@ -157,6 +157,38 @@ final class OffsetWindowFunctionFrame(
override def currentUpperBound(): Int = throw new
UnsupportedOperationException()
}
+class FixedOffsetWindowFunctionFrame(
+ target: InternalRow,
+ ordinal: Int,
+ expressions: Array[OffsetWindowFunction],
+ inputSchema: Seq[Attribute],
+ newMutableProjection: (Seq[Expression], Seq[Attribute]) =>
MutableProjection,
+ offset: Int)
+ extends OffsetWindowFunctionFrame(
+ target, ordinal, expressions, inputSchema, newMutableProjection, offset) {
+
+ override def prepare(rows: ExternalAppendOnlyUnsafeRowArray): Unit = {
+ input = rows
+ inputIndex = 0
+ }
+
+ override def write(index: Int, current: InternalRow): Unit = {
Review comment:
Because the behavior of `NTH_VALUE/FIRST_VALUE/LAST_VALUE` more similar to
`LEAD/LAG`, so I make `FixedOffsetWindowFunctionFrame` extends
`OffsetWindowFunctionFrame`. `OffsetWindowFunctionFrame` only to fetch projects
but `UnboundedWindowFunctionFrame` will `update` and `execute` expressions.
If you think so, I can abstract a base class for
`FixedOffsetWindowFunctionFrame` and `OffsetWindowFunctionFrame`.
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