Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/11105#discussion_r55434271
--- Diff: core/src/main/scala/org/apache/spark/Accumulable.scala ---
@@ -53,42 +54,79 @@ import org.apache.spark.util.Utils
* for system and time metrics like serialization
time or bytes spilled,
* and false for things with absolute values like
number of input rows.
* This should be used for internal metrics only.
- * @tparam R the full accumulated data (result type)
+ * @param consistent if this [[Accumulable]] is consistent. Consistent
[[Accumulable]]s will only
+ * have values added once for each RDD/Partition
execution combination. This
+ * prevents double counting on reevaluation. Partial
evaluation of a partition
+ * will not increment a consistent [[Accumulable]].
Consistent [[Accumulable]]s
+ * are currently experimental and the behaviour may
change in future versions.
+ * Consistent [[Accumulable]]s can only be added to
inside is
+ * [[MapPartitionsRDD]]s and are designed for counting
"data properties".
+ * @tparam R the full accumulated data
* @tparam T partial data that can be added in
*/
-class Accumulable[R, T] private (
+class Accumulable[R, T] private[spark] (
val id: Long,
// SI-8813: This must explicitly be a private val, or else scala 2.11
doesn't compile
@transient private val initialValue: R,
param: AccumulableParam[R, T],
val name: Option[String],
internal: Boolean,
- private[spark] val countFailedValues: Boolean)
+ private[spark] val countFailedValues: Boolean,
+ private[spark] val consistent: Boolean)
extends Serializable {
private[spark] def this(
- initialValue: R,
+ @transient initialValue: R,
--- End diff --
I think this annotation isn't necssary in helper constructors (since its
just a method param, not doubling as a variable declaration), though I am not
positive. At least, it wasn't there before, so I guess I'd like some evidence
that its necessary now :)
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