jackwener commented on code in PR #7428:
URL: https://github.com/apache/arrow-datafusion/pull/7428#discussion_r1307271741
##########
datafusion/core/src/physical_plan/projection.rs:
##########
@@ -410,12 +415,39 @@ fn stats_projection(
.collect()
});
- Statistics {
- is_exact: stats.is_exact,
- num_rows: stats.num_rows,
- column_statistics,
- // TODO stats: knowing the type of the new columns we can guess the
output size
- total_byte_size: None,
+ let primitive_row_size = inner_exprs
+ .clone()
+ .into_iter()
+ .map(|e| match e.data_type(schema.as_ref()) {
+ Ok(data_type) => data_type.primitive_width(),
+ Err(_) => None,
+ })
+ .fold(Some(0usize), |init, v| match (init, v) {
+ (Some(l), Some(r)) => Some(l + r),
+ _ => None,
+ });
+
+ match (primitive_row_size, stats.num_rows) {
+ (Some(row_size), Some(row_count)) => {
+ Statistics {
+ is_exact: stats.is_exact,
+ num_rows: stats.num_rows,
+ column_statistics,
+ // Use the row_size * row_count as the total byte size
+ total_byte_size: Some(row_size * row_count),
+ }
+ }
+ _ => {
+ Statistics {
+ is_exact: stats.is_exact,
+ num_rows: stats.num_rows,
+ column_statistics,
+ // TODO stats: knowing the type of the new columns we can
guess the output size
+ // If we can't get the exact statistics for the project
+ // Before we get the exact result, we just use the child status
+ total_byte_size: stats.total_byte_size,
Review Comment:
I think they are different things.
`stats.is_exact` is for the whole statistic. Current `num_rows` is exact.
Maybe we need add Unknow status for `total_byte_size`.
such as Presto:
```
PlanNodeStatsEstimate UNKNOWN. It's present `Unknown` for whole statistic.
SymbolStatsEstimate UNKNOWN. It's present `Unknown` for single expr
statistic.
```
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