Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3743#discussion_r112571486
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/windows.scala
---
@@ -22,6 +22,126 @@ import org.apache.flink.table.expressions.{Expression,
ExpressionParser}
import org.apache.flink.table.plan.logical._
/**
+ * An over window specification.
+ *
+ * Over window is similar to the traditional OVER SQL.
+ */
+class OverWindow {
+
+ private[flink] var alias: Expression = _
+ private[flink] var partitionBy: Seq[Expression] = Seq[Expression]()
+ private[flink] var orderBy: Expression = _
+ private[flink] var preceding: Expression = _
+ private[flink] var following: Expression = null
+
+ /**
+ * Assigns an alias for this window that the following `select()`
clause can refer to.
+ *
+ * @param alias alias for this over window
+ * @return this over window
+ */
+ def as(alias: String): OverWindow =
as(ExpressionParser.parseExpression(alias))
+
+ /**
+ * Assigns an alias for this window that the following `select()`
clause can refer to.
+ *
+ * @param alias alias for this over window
+ * @return this over window
+ */
+ def as(alias: Expression): OverWindow = {
+ this.alias = alias
+ this
+ }
+
+ /**
+ * Partitions the elements on some partition keys.
+ *
+ * @param partitionBy
+ * @return this over window
+ */
+ def partitionBy(partitionBy: String): OverWindow = {
+ this.partitionBy(ExpressionParser.parseExpression(partitionBy))
+ }
+
+ /**
+ * Partitions the elements on some partition keys.
+ *
+ * @param partitionBy
+ * @return this over window
+ */
+ def partitionBy(partitionBy: Expression*): OverWindow = {
+ this.partitionBy = partitionBy
+ this
+ }
+
+
+ /**
+ * Specifies the time mode.
+ *
+ * @param orderBy For streaming tables call [[orderBy 'rowtime or
orderBy 'proctime]]
+ * to specify time mode.
+ * @return this over window
+ */
+ def orderBy(orderBy: String): OverWindow = {
+ this.orderBy(ExpressionParser.parseExpression(orderBy))
+ }
+
+ /**
+ * Specifies the time mode.
+ *
+ * @param orderBy For streaming tables call [[orderBy 'rowtime or
orderBy 'proctime]]
+ * to specify time mode.
+ * @return this over window
+ */
+ def orderBy(orderBy: Expression): OverWindow = {
+ this.orderBy = orderBy
+ this
+ }
+
+ /**
+ * Set the preceding offset (based on time or row-count intervals) for
over window
+ *
+ * @param preceding forward offset that relative to the current row
+ * @return this over window
+ */
+ def preceding(preceding: String): OverWindow = {
+ this.preceding(ExpressionParser.parseExpression(preceding))
+ }
+
+ /**
+ * Set the preceding offset (based on time or row-count intervals) for
over window
+ *
+ * @param preceding forward offset that relative to the current row
+ * @return this over window
+ */
+ def preceding(preceding: Expression): OverWindow = {
+ this.preceding = preceding
+ this
+ }
+
+ /**
+ * Set the following offset (based on time or row-count intervals) for
over window
+ *
+ * @param following subsequent offset that relative to the current row
+ * @return this over window
+ */
+ def following(following: String): OverWindow = {
--- End diff --
Should we make `following` optional and default to CURRENT_ROW /
CURRENT_RANGE depending on the type of `preceding`? I think that would be a
nice shortcut and also be aligned with SQL.
What do you think @sunjincheng121 ?
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