xudong963 commented on code in PR #15539:
URL: https://github.com/apache/datafusion/pull/15539#discussion_r2036278558
##########
datafusion/datasource/src/statistics.rs:
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@@ -410,23 +410,24 @@ pub async fn get_statistics_with_limit(
}
/// Generic function to compute statistics across multiple items that have
statistics
-fn compute_summary_statistics<T, I>(
+/// If `items` is empty or all items don't have statistics, it returns `None`.
Review Comment:
> If you don't have a schema, how can you even try to compute a statistics,
I couldn't imagine also that
For the `compute_summary_statistics` method, it does only summarize, it's
not necessary to have the schema.
For the caller of `compute_summary_statistics`, such as
`compute_file_group_statistics`, if `compute_summary_statistics` returns none,
it doesn't need to do anything, because the default value of the statistics of
FileGroup is None
```rust
pub struct FileGroup {
/// The files in this group
files: Vec<PartitionedFile>,
/// Optional statistics for the data across all files in the group
statistics: Option<Arc<Statistics>>,
}
```
It is used as a base method, and its caller has the flexibility to treat it
according to its return value, without restricting it too much (e.g., requiring
a shcema)
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