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[SPARK-17182][SQL] Mark Collect as non-deterministic #14749

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[SPARK-17182][SQL] Mark Collect as non-deterministic #14749

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4 changes: 4 additions & 0 deletions ...catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/collect.scala
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Expand Up @@ -54,6 +54,10 @@ abstract class Collect extends ImperativeAggregate {

override def inputAggBufferAttributes: Seq[AttributeReference] = Nil

// Both `CollectList` and `CollectSet` are non-deterministic since their results depend on the
// actual order of input rows.
override def deterministic: Boolean = false
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@hvanhovell hvanhovell Aug 22, 2016

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Is collect_set non deterministic? It is backed by a HashSet, and the way elements are iterated over does not rely on the input order.

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@hvanhovell hvanhovell Aug 22, 2016

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NVM. Actually iteration over a set is non-deterministic for values in the same hash bucket.

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@liancheng liancheng Aug 23, 2016

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Yea. Also, there's no set type in Spark SQL, thus the result set is actually just a list without duplicated elements.


protected[this] val buffer: Growable[Any] with Iterable[Any]

override def initialize(b: MutableRow): Unit = {
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