rdettai commented on a change in pull request #965:
URL: https://github.com/apache/arrow-datafusion/pull/965#discussion_r706860091
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File path: datafusion/src/physical_plan/union.rs
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@@ -106,16 +109,68 @@ impl ExecutionPlan for UnionExec {
}
}
}
+
+ fn statistics(&self) -> Statistics {
+ self.inputs
+ .iter()
+ .map(|ep| ep.statistics())
+ .reduce(stats_union)
Review comment:
thanks 😉
##########
File path: datafusion/src/physical_plan/mod.rs
##########
@@ -89,6 +89,34 @@ impl Stream for EmptyRecordBatchStream {
/// Physical planner interface
pub use self::planner::PhysicalPlanner;
+/// Statistics for an physical plan node
+/// Fields are optional and can be inexact because the sources
+/// sometimes provide approximate estimates for performance reasons
+/// and the transformations output are not always predictable.
+#[derive(Debug, Clone, Default, PartialEq)]
+pub struct Statistics {
+ /// The number of table rows
+ pub num_rows: Option<usize>,
+ /// total byte of the table rows
+ pub total_byte_size: Option<usize>,
+ /// Statistics on a column level
+ pub column_statistics: Option<Vec<ColumnStatistics>>,
+ /// Some datasources or transformations might provide inexact estimates
Review comment:
See
https://github.com/apache/arrow-datafusion/pull/965#issuecomment-917665454
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