xudong963 commented on code in PR #17061:
URL: https://github.com/apache/datafusion/pull/17061#discussion_r2290663739
##########
datafusion/physical-plan/src/repartition/mod.rs:
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@@ -755,10 +756,40 @@ impl ExecutionPlan for RepartitionExec {
}
fn partition_statistics(&self, partition: Option<usize>) ->
Result<Statistics> {
- if partition.is_none() {
- self.input.partition_statistics(None)
+ if let Some(partition) = partition {
+ let partition_count = self.partitioning().partition_count();
+ if partition >= partition_count {
+ return internal_err!(
+ "RepartitionExec invalid partition {} (expected less than
{})",
+ partition,
+ self.partitioning().partition_count()
+ );
+ }
+
+ let mut stats = self.input.partition_statistics(None)?;
+
+ // Distribute statistics across partitions
+ stats.num_rows = stats
+ .num_rows
+ .get_value()
+ .map(|rows| Precision::Inexact(rows / partition_count))
+ .unwrap_or(Precision::Absent);
+ stats.total_byte_size = stats
+ .total_byte_size
+ .get_value()
+ .map(|bytes| Precision::Inexact(bytes / partition_count))
Review Comment:
I think for the case `partition_count` is 0, it's better to return unknown
statistics, which means the child node is empty and doesn't have data.
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