limit the scan threads if there are small parts

src/query/storages/common/table-meta/src/meta/v2/segment.rs

@@ -93,15 +93,6 @@ impl BlockMeta {
     pub fn compression(&self) -> Compression {
         self.compression
     }
-
-    // true read_rows, maybe a range from a block
-    pub fn read_rows(&self, range: &Option<Range<usize>>) -> u64 {
-        self.col_metas
-            .iter()
-            .next()
-            .map(|(_, m)| m.read_rows(range))
-            .unwrap_or(self.row_count)
-    }
 }
 
 #[derive(serde::Serialize, serde::Deserialize, Clone, Debug, Eq, PartialEq, EnumAsInner)]

src/query/storages/fuse/src/operations/read/fuse_source.rs

@@ -234,11 +234,19 @@ pub fn adjust_threads_and_request(
         // If the read bytes of a partition is small enough, less than 16k rows
         // we will not use an extra heavy thread to process it.
         // now only works for native reader
-        static MIN_ROWS_READ_PER_THREAD: usize = 16 * 1024;
+        static MIN_ROWS_READ_PER_THREAD: u64 = 16 * 1024;
         if is_native {
             plan.parts.partitions.iter().for_each(|part| {
                 if let Some(part) = part.as_any().downcast_ref::<FusePartInfo>() {
-                    if part.nums_rows < MIN_ROWS_READ_PER_THREAD {
+                    let to_read_rows = part
+                        .columns_meta
+                        .iter()
+                        .map(|(_, meta)| meta.read_rows(&part.range))
+                        .filter(|rows| *rows > 0)
+                        .next()
+                        .unwrap_or(part.nums_rows as u64);
+
+                    if to_read_rows < MIN_ROWS_READ_PER_THREAD {
                         block_nums -= 1;
                     }
                 }

src/query/storages/fuse/src/operations/read_partitions.rs

@@ -381,7 +381,7 @@ impl FuseTable {
             }
         }
 
-        let rows_count = meta.read_rows(&range);
+        let rows_count = meta.row_count;
         let location = meta.location.0.clone();
         let format_version = meta.location.1;
 
@@ -420,7 +420,7 @@ impl FuseTable {
             }
         }
 
-        let rows_count = meta.read_rows(&range);
+        let rows_count = meta.row_count;
         let location = meta.location.0.clone();
         let format_version = meta.location.1;