Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/9038#discussion_r42032759
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TungstenAggregationIterator.scala
---
@@ -481,10 +610,10 @@ class TungstenAggregationIterator(
// When needsProcess is false, the format of input rows is
groupingKey + aggregation buffer.
// We need to project the aggregation buffer part from an input row.
val buffer = createNewAggregationBuffer()
- // The originalInputAttributes are using cloneBufferAttributes. So,
we need to use
- // allAggregateFunctions.flatMap(_.cloneBufferAttributes).
+ // The originalInputAttributes are using inputAggBufferAttributes.
So, we need to use
+ // allAggregateFunctions.flatMap(_.inputAggBufferAttributes).
val bufferExtractor = newMutableProjection(
- allAggregateFunctions.flatMap(_.inputAggBufferAttributes),
+ originalInputAttributes.drop(initialInputBufferOffset),
--- End diff --
Had a discussion with @JoshRosen offline. Here is the explaining for this
change.
Our `ImperativeAggregate` and `DeclarativeAggregate` are quite different.
For an `ImperativeAggregate`, its correctness is based on the correctness of
`mutableAggBufferOffset` and `inputAggBufferOffset`, and when there is no
fallback, it does not rely on attribute ids for binding. To make
`mutableAggBufferOffset` and `inputAggBufferOffset` immutable, whenever we call
`withNewMutableAggBufferOffset` and `withNewInputAggBufferOffset`, we create a
new copy of the `ImperativeAggregate`. Although a new copy contains a new set
of attribute ids for `aggBufferAttributes` and `inputAggBufferAttributes`, in
most cases, those new ids do not introduce any problem because an
`ImperativeAggregate` does not rely on these ids. However, once we fallback to
sort-based aggregation and we need to extract input aggregation buffers, we
need to have matching attribute ids to make it work. Since
`allAggregateFunctions.flatMap(_.inputAggBufferAttributes)` will have
attributes with a new set of ids, we w
ill see a binding error at here.
`originalInputAttributes.drop(initialInputBufferOffset)` is fine at here.
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