Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/9215#discussion_r42892965
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/metric/SQLMetrics.scala
---
@@ -62,7 +67,19 @@ private[sql] trait SQLMetricValue[T] extends
Serializable {
private[sql] class LongSQLMetricValue(private var _value : Long) extends
SQLMetricValue[Long] {
def add(incr: Long): LongSQLMetricValue = {
- _value += incr
+ // Some LongSQLMetric will use -1 as initial value, so if the
accumulator is never updated,
+ // we can filter it out later. However, when `add` is called, the
accumulator is valid, we
+ // should turn -1 to 0.
+ if (_value < 0) {
+ _value = 0
+ }
+
+ // Some LongSQLMetric will use -1 as initial value, when we merge
accumulator updates at driver
+ // side, we should ignore these -1 values.
+ if (incr > 0) {
+ _value += incr
+ }
+
--- End diff --
@cloud-fan sorry. I just realized that this method is in the critical path
(when we calculate numRows). How about we remove this change and document it
clear that those negative initial values will have a small impact on the sum of
memory consumption?
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