marvinlanhenke commented on code in PR #10852:
URL: https://github.com/apache/datafusion/pull/10852#discussion_r1634245246
##########
datafusion/core/src/datasource/physical_plan/parquet/statistics.rs:
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@@ -517,6 +518,72 @@ macro_rules! get_statistics {
}}}
}
+macro_rules! make_data_page_stats_iterator {
+ ($iterator_type: ident, $func: ident, $index_type: path, $stat_value_type:
ty) => {
+ struct $iterator_type<'a, I>
+ where
+ I: Iterator<Item = &'a Index>,
+ {
+ iter: I,
+ }
+
+ impl<'a, I> $iterator_type<'a, I>
+ where
+ I: Iterator<Item = &'a Index>,
+ {
+ fn new(iter: I) -> Self {
+ Self { iter }
+ }
+ }
+
+ impl<'a, I> Iterator for $iterator_type<'a, I>
+ where
+ I: Iterator<Item = &'a Index>,
+ {
+ type Item = Vec<Option<$stat_value_type>>;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let next = self.iter.next();
+ match next {
+ Some(index) => match index {
+ $index_type(native_index) => Some(
+ native_index
+ .indexes
+ .iter()
+ .map(|x| x.$func)
+ .collect::<Vec<_>>(),
+ ),
+ // No matching `Index` found.
+ // Thus no statistics that can be extracted.
+ // We return vec![None] to effectively
+ // create an arrow null-array.
+ _ => Some(vec![None]),
Review Comment:
Yes, you're right - and we definitely need test coverage here (I'm still
confused sometimes (actually all the time) about this logic 🤯).
However, I think we need a different approach since we wouldn't have access
to `native_index.indexes`, if we cannot match the index, or we encounter the
`Index::NONE` variant.
Based on the implementation in `page_filter.rs`
[here](https://github.com/apache/datafusion/blob/main/datafusion/core/src/physical_optimizer/pruning.rs#L885-L893)
we should probably construct a `vec![None; len]` where `len =
page_offset_index.len()` and `page_offset_index: Vec<PageLocation>`.
I'll try make some changes here (also the API needs to change slightly) and
we can discuss further?
I'll also try to make a test-case with multiple data_pages per row_group
(haven't found the setting, yet...)
WDYT @alamb
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