Dandandan commented on a change in pull request #1063:
URL: https://github.com/apache/arrow-datafusion/pull/1063#discussion_r720259316
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File path: datafusion/src/physical_optimizer/aggregate_statistics.rs
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@@ -153,6 +159,37 @@ fn take_optimizable_count(
None
}
+fn take_optimizable_count_with_nulls(
+ agg_expr: &dyn AggregateExpr,
+ stats: &Statistics,
+) -> Option<(ScalarValue, String)> {
+ if let (Some(num_rows), Some(col_stats), Some(casted_expr)) = (
+ stats.num_rows,
+ &stats.column_statistics,
+ agg_expr.as_any().downcast_ref::<expressions::Min>(),
+ ) {
+ if casted_expr.expressions().len() == 1 {
+ // TODO optimize with exprs other than Column
+ if let Some(col_expr) = casted_expr.expressions()[0]
+ .as_any()
+ .downcast_ref::<expressions::Column>()
+ {
+ if let ColumnStatistics {
+ null_count: Some(val),
+ ..
+ } = &col_stats[col_expr.index()]
+ {
+ return Some((
+ ScalarValue::UInt64(Some((num_rows - val) as u64)),
+ "COUNT(Uint8(1))".to_string(),
Review comment:
I think it should be the column name here indeed for it to work.
The current way hash aggregates work is by accessing the value of the
aggregate in a projection by the name generated by the expression in the
aggregate (e.g. `COUNT(UInt8(1))` for `count(*)` but `COUNT(col)` for a non
null count. So by rewriting and giving it the same name, this avoids computing
the aggregate while still being compatible with the usage of the aggregate in
the projection.
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