rangadi commented on code in PR #40561:
URL: https://github.com/apache/spark/pull/40561#discussion_r1160032216
##########
sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala:
##########
@@ -3038,6 +3025,107 @@ class Dataset[T] private[sql](
dropDuplicates(colNames)
}
+ /**
+ * Returns a new Dataset with duplicates rows removed, within watermark.
+ *
+ * For a static batch [[Dataset]], it just drops duplicate rows. For a
streaming [[Dataset]],
+ * this will keep all data across triggers as intermediate state to drop
duplicated rows. The
+ * state will be kept to guarantee the semantic, "Events are deduplicated as
long as the time
+ * distance of earliest and latest events are smaller than the delay
threshold of watermark."
+ * The watermark for the input [[Dataset]] must be set via
[[withWatermark]]. Users are
+ * encouraged to set the delay threshold of watermark longer than max
timestamp differences
+ * among duplicated events. In addition, too late data older than watermark
will be dropped.
+ *
+ * @group typedrel
+ * @since 3.5.0
+ */
+ def dropDuplicatesWithinWatermark(): Dataset[T] = {
+ dropDuplicatesWithinWatermark(this.columns)
+ }
+
+ /**
+ * Returns a new Dataset with duplicates rows removed, considering only the
subset of columns,
+ * within watermark.
+ *
+ * For a static batch [[Dataset]], it just drops duplicate rows. For a
streaming [[Dataset]],
+ * this will keep all data across triggers as intermediate state to drop
duplicated rows. The
+ * state will be kept to guarantee the semantic, "Events are deduplicated as
long as the time
+ * distance of earliest and latest events are smaller than the delay
threshold of watermark."
+ * The watermark for the input [[Dataset]] must be set via
[[withWatermark]]. Users are
+ * encouraged to set the delay threshold of watermark longer than max
timestamp differences
+ * among duplicated events. In addition, too late data older than watermark
will be dropped.
Review Comment:
It is statement on how watermark works, not related to dropDuplicatate(). R
May be better to say 'Note that ...' rather than 'In addition ...'
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