Dandandan commented on a change in pull request #9806:
URL: https://github.com/apache/arrow/pull/9806#discussion_r606780118
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File path: rust/datafusion/src/physical_plan/union.rs
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@@ -60,15 +60,31 @@ impl ExecutionPlan for UnionExec {
/// Output of the union is the combination of all output partitions of the
inputs
fn output_partitioning(&self) -> Partitioning {
- // Sums all the output partitions
- let num_partitions = self
- .inputs
+ let intial: Option<Partitioning> = None;
+ self.inputs
.iter()
- .map(|plan| plan.output_partitioning().partition_count())
- .sum();
- // TODO: this loses partitioning info in case of same partitioning
scheme (for example `Partitioning::Hash`)
- // https://issues.apache.org/jira/browse/ARROW-11991
- Partitioning::UnknownPartitioning(num_partitions)
+ .fold(intial, |acc, input| {
+ match (acc, input.output_partitioning()) {
+ (None, partition) => Some(partition),
+ (
+ Some(Partitioning::Hash(mut vector_acc, size_acc)),
+ Partitioning::Hash(vector, size),
+ ) => {
+ vector_acc.append(&mut vector.clone());
+ Some(Partitioning::Hash(vector_acc, size_acc + size))
+ }
+ (
+ Some(Partitioning::RoundRobinBatch(size_acc)),
+ Partitioning::RoundRobinBatch(size),
+ ) => Some(Partitioning::RoundRobinBatch(size_acc + size)),
Review comment:
So it doesn't say anything about this batch size, only he number of
partitions.
The implementation of the Union creates the sum of input partitions as
output, so each partition can be executed in parallel, so if we have 10
partitions in `a` and 20 in `b`, the `a UNION b` will have 30 partitions.
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