[HSTACK] - consolidate partitions if we have many small files

Author: aditanase

datafusion/datasource/src/file_groups.rs

@@ -213,7 +213,13 @@ impl FileGroupPartitioner {
             .iter()
             .map(|f| f.object_meta.size as i64)
             .sum::<i64>();
-        if total_size < (repartition_file_min_size as i64) || total_size == 0 {
+
+        // bail if we are asked to *split* a set of files that are already too small
+        // if we are being asked to consolidate, we proceed
+        if (total_size < (repartition_file_min_size as i64)
+            && target_partitions >= file_groups.len())
+            || total_size == 0
+        {
             return None;
         }
 
@@ -228,30 +234,46 @@ impl FileGroupPartitioner {
             .scan(
                 (current_partition_index, current_partition_size),
                 |state, source_file| {
-                    let mut produced_files = vec![];
-                    let mut range_start = 0;
-                    while range_start < source_file.object_meta.size {
-                        let range_end = min(
-                            range_start + (target_partition_size - state.1),
-                            source_file.object_meta.size,
-                        );
-
-                        let mut produced_file = source_file.clone();
-                        produced_file.range = Some(FileRange {
-                            start: range_start as i64,
-                            end: range_end as i64,
-                        });
-                        produced_files.push((state.0, produced_file));
-
-                        if state.1 + (range_end - range_start) >= target_partition_size {
+                    // Skip splitting files smaller than repartition_file_min_size
+                    // This may result in a few more partitions than requested (maybe 1 more)
+                    if source_file.object_meta.size > 0
+                        && source_file.object_meta.size < repartition_file_min_size
+                    {
+                        state.1 += source_file.object_meta.size;
+                        if state.1 > target_partition_size {
                             state.0 += 1;
                             state.1 = 0;
-                        } else {
-                            state.1 += range_end - range_start;
                         }
-                        range_start = range_end;
+                        let small_file = (state.0, source_file.clone());
+                        Some(vec![small_file])
+                    } else {
+                        let mut produced_files = vec![];
+                        let mut range_start = 0;
+                        while range_start < source_file.object_meta.size {
+                            let range_end = min(
+                                range_start + (target_partition_size - state.1),
+                                source_file.object_meta.size,
+                            );
+
+                            let mut produced_file = source_file.clone();
+                            produced_file.range = Some(FileRange {
+                                start: range_start as i64,
+                                end: range_end as i64,
+                            });
+                            produced_files.push((state.0, produced_file));
+
+                            if state.1 + (range_end - range_start)
+                                >= target_partition_size
+                            {
+                                state.0 += 1;
+                                state.1 = 0;
+                            } else {
+                                state.1 += range_end - range_start;
+                            }
+                            range_start = range_end;
+                        }
+                        Some(produced_files)
                     }
-                    Some(produced_files)
                 },
             )
             .flatten()