berkaysynnada commented on code in PR #15473:
URL: https://github.com/apache/datafusion/pull/15473#discussion_r2030077255
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datafusion/datasource/src/file_scan_config.rs:
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@@ -858,6 +858,96 @@ impl FileScanConfig {
})
}
+ /// Splits file groups into new groups based on statistics to enable
efficient parallel processing.
+ ///
+ /// The method distributes files across a target number of partitions
while ensuring
+ /// files within each partition maintain sort order based on their min/max
statistics.
+ ///
+ /// The algorithm works by:
+ /// 1. Takes files sorted by minimum values
+ /// 2. For each file:
+ /// - Finds eligible groups (empty or where file's min > group's last
max)
+ /// - Selects the smallest eligible group
+ /// - Creates a new group if needed
+ ///
+ /// # Parameters
+ /// * `table_schema`: Schema containing information about the columns
+ /// * `file_groups`: The original file groups to split
+ /// * `sort_order`: The lexicographical ordering to maintain within each
group
+ /// * `target_partitions`: The desired number of output partitions
+ ///
+ /// # Returns
+ /// A new set of file groups, where files within each group are
non-overlapping with respect to
+ /// their min/max statistics and maintain the specified sort order.
+ pub fn split_groups_by_statistics_with_target_partitions(
+ table_schema: &SchemaRef,
+ file_groups: &[FileGroup],
+ sort_order: &LexOrdering,
+ target_partitions: usize,
Review Comment:
Do we really need `target_partitions` as a parameter here? I think if this
function takes that, it should return `Result<Option<...>>`, in case of the
groups cannot split into the given partition count, being ordered (so we
shouldn't check that at the caller side).
The other option is removing that parameter, since the same logic can be
written without that (no need to initiate the `file_groups_indices` based on
this count)
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