I just find that MutableAggregationBuffer.update will convert data for every
update, which is terrible when I use something like Map, Array.
It is hard to implement a collect_set udaf, which will be O(n^2) in this
convert semantic.
Any advice?
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https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/Aggregate.scala#L85
I can't understand this code, it seems to be a "bug", but group by of
SparkSQL just works fine.
with code below, some expressions are mapping to AttributeReferences, then
"bindRe
Got it.
Only NamedExpression have exprId, we have to make new Attribute here.
private[this] val computedSchema = computedAggregates.map(_.resultAttribute)
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