refactor: scan Batches directly (#6369)

* refactor: scan `Batch`es directly

Signed-off-by: luofucong <luofc@foxmail.com>

* fix ci

Signed-off-by: luofucong <luofc@foxmail.com>

* resolve PR comments

Signed-off-by: luofucong <luofc@foxmail.com>

* resolve PR comments

Signed-off-by: luofucong <luofc@foxmail.com>

---------

Signed-off-by: luofucong <luofc@foxmail.com>

src/store-api/src/storage/requests.rs

@@ -67,14 +67,34 @@ pub struct ScanRequest {
 
 impl Display for ScanRequest {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(f, "ScanRequest {{")?;
+        enum Delimiter {
+            None,
+            Init,
+        }
+
+        impl Delimiter {
+            fn as_str(&mut self) -> &str {
+                match self {
+                    Delimiter::None => {
+                        *self = Delimiter::Init;
+                        ""
+                    }
+                    Delimiter::Init => ", ",
+                }
+            }
+        }
+
+        let mut delimiter = Delimiter::None;
+
+        write!(f, "ScanRequest {{ ")?;
         if let Some(projection) = &self.projection {
-            write!(f, "projection: {:?},", projection)?;
+            write!(f, "{}projection: {:?}", delimiter.as_str(), projection)?;
         }
         if !self.filters.is_empty() {
             write!(
                 f,
-                ", filters: [{}]",
+                "{}filters: [{}]",
+                delimiter.as_str(),
                 self.filters
                     .iter()
                     .map(|f| f.to_string())
@@ -83,23 +103,90 @@ impl Display for ScanRequest {
             )?;
         }
         if let Some(output_ordering) = &self.output_ordering {
-            write!(f, ", output_ordering: {:?}", output_ordering)?;
+            write!(
+                f,
+                "{}output_ordering: {:?}",
+                delimiter.as_str(),
+                output_ordering
+            )?;
         }
         if let Some(limit) = &self.limit {
-            write!(f, ", limit: {}", limit)?;
+            write!(f, "{}limit: {}", delimiter.as_str(), limit)?;
         }
         if let Some(series_row_selector) = &self.series_row_selector {
-            write!(f, ", series_row_selector: {}", series_row_selector)?;
+            write!(
+                f,
+                "{}series_row_selector: {}",
+                delimiter.as_str(),
+                series_row_selector
+            )?;
         }
         if let Some(sequence) = &self.sequence {
-            write!(f, ", sequence: {}", sequence)?;
+            write!(f, "{}sequence: {}", delimiter.as_str(), sequence)?;
         }
         if let Some(sst_min_sequence) = &self.sst_min_sequence {
-            write!(f, ", sst_min_sequence: {}", sst_min_sequence)?;
+            write!(
+                f,
+                "{}sst_min_sequence: {}",
+                delimiter.as_str(),
+                sst_min_sequence
+            )?;
         }
         if let Some(distribution) = &self.distribution {
-            write!(f, ", distribution: {}", distribution)?;
+            write!(f, "{}distribution: {}", delimiter.as_str(), distribution)?;
         }
-        write!(f, "}}")
+        write!(f, " }}")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use datafusion_expr::{binary_expr, col, lit, Operator};
+
+    use super::*;
+
+    #[test]
+    fn test_display_scan_request() {
+        let request = ScanRequest {
+            ..Default::default()
+        };
+        assert_eq!(request.to_string(), "ScanRequest {  }");
+
+        let request = ScanRequest {
+            projection: Some(vec![1, 2]),
+            filters: vec![
+                binary_expr(col("i"), Operator::Gt, lit(1)),
+                binary_expr(col("s"), Operator::Eq, lit("x")),
+            ],
+            limit: Some(10),
+            ..Default::default()
+        };
+        assert_eq!(
+            request.to_string(),
+            r#"ScanRequest { projection: [1, 2], filters: [i > Int32(1), s = Utf8("x")], limit: 10 }"#
+        );
+
+        let request = ScanRequest {
+            filters: vec![
+                binary_expr(col("i"), Operator::Gt, lit(1)),
+                binary_expr(col("s"), Operator::Eq, lit("x")),
+            ],
+            limit: Some(10),
+            ..Default::default()
+        };
+        assert_eq!(
+            request.to_string(),
+            r#"ScanRequest { filters: [i > Int32(1), s = Utf8("x")], limit: 10 }"#
+        );
+
+        let request = ScanRequest {
+            projection: Some(vec![1, 2]),
+            limit: Some(10),
+            ..Default::default()
+        };
+        assert_eq!(
+            request.to_string(),
+            "ScanRequest { projection: [1, 2], limit: 10 }"
+        );
     }
 }