feat: Adds RegionScanner trait (#3948)

* feat: define region scanner

* feat: single partition scanner

* feat: use single partition scanner

* feat: implement ExecutionPlan wip

* feat: mito engine returns single partition scanner

* feat: implement DisplayAs for region server

* feat: dummy table provider use handle_partitioned_query()

* test: update sqlness test

* feat: table provider use ReadFromRegion

* refactor: remove StreamScanAdapter

* chore: update lock

* style: fix clippy

* refactor: remove handle_query from the RegionEngine trait

* chore: address CR comments

* refactor: rename methods

* refactor: rename ReadFromRegion to RegionScanExec

src/file-engine/src/engine.rs

@@ -25,7 +25,9 @@ use common_telemetry::{error, info};
 use object_store::ObjectStore;
 use snafu::{ensure, OptionExt};
 use store_api::metadata::RegionMetadataRef;
-use store_api::region_engine::{RegionEngine, RegionRole, SetReadonlyResponse};
+use store_api::region_engine::{
+    RegionEngine, RegionRole, RegionScannerRef, SetReadonlyResponse, SinglePartitionScanner,
+};
 use store_api::region_request::{
     AffectedRows, RegionCloseRequest, RegionCreateRequest, RegionDropRequest, RegionOpenRequest,
     RegionRequest,
@@ -49,6 +51,20 @@ impl FileRegionEngine {
             inner: Arc::new(EngineInner::new(object_store)),
         }
     }
+
+    async fn handle_query(
+        &self,
+        region_id: RegionId,
+        request: ScanRequest,
+    ) -> Result<SendableRecordBatchStream, BoxedError> {
+        self.inner
+            .get_region(region_id)
+            .await
+            .context(RegionNotFoundSnafu { region_id })
+            .map_err(BoxedError::new)?
+            .query(request)
+            .map_err(BoxedError::new)
+    }
 }
 
 #[async_trait]
@@ -72,14 +88,10 @@ impl RegionEngine for FileRegionEngine {
         &self,
         region_id: RegionId,
         request: ScanRequest,
-    ) -> Result<SendableRecordBatchStream, BoxedError> {
-        self.inner
-            .get_region(region_id)
-            .await
-            .context(RegionNotFoundSnafu { region_id })
-            .map_err(BoxedError::new)?
-            .query(request)
-            .map_err(BoxedError::new)
+    ) -> Result<RegionScannerRef, BoxedError> {
+        let stream = self.handle_query(region_id, request).await?;
+        let scanner = Arc::new(SinglePartitionScanner::new(stream));
+        Ok(scanner)
     }
 
     async fn get_metadata(&self, region_id: RegionId) -> Result<RegionMetadataRef, BoxedError> {