adriangb commented on code in PR #22300:
URL: https://github.com/apache/datafusion/pull/22300#discussion_r3305926917
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datafusion/expr-common/src/statistics.rs:
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@@ -1694,3 +1694,44 @@ mod tests {
all_ops.into_iter().collect()
}
}
+
+// ---------------------------------------------------------------------------
+// Query-aware statistics requests.
+//
+// A small extension to the existing `Statistics` model: instead of "give me
+// everything you have for every column", a caller can ask for a specific list
+// of stats by name. `StatisticsRequest` is just that vocabulary — DataFusion
+// itself does not populate or consume it. It exists so a request can be
+// threaded from a `TableScan` (see `TableScan::statistics_requests`) through
+// `ScanArgs::statistics_requests` to a `TableProvider`, which is enough for a
+// query-aware statistics feature to be implemented outside of DataFusion.
+// ---------------------------------------------------------------------------
+
+use datafusion_common::Column;
+
+/// A statistic a caller would like a provider to supply, if it can do so
+/// cheaply.
+///
+/// Each variant maps onto a field of [`datafusion_common::Statistics`] /
+/// [`datafusion_common::ColumnStatistics`], so a provider that already
+/// populates one can answer the request trivially.
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum StatisticsRequest {
+ /// Smallest non-null value of `column`.
+ Min(Column),
Review Comment:
Will do
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