From 64ae32def0ea237d847bc0c101fc3571667f9dc4 Mon Sep 17 00:00:00 2001
From: Ruihang Xia <waynestxia@gmail.com>
Date: Wed, 28 Aug 2024 16:52:09 +0800
Subject: [PATCH] feat: remove some redundent clone/conversion on constructing
 MergeScan stream (#4632)

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>
---
 src/query/src/dist_plan/merge_scan.rs | 34 +++++++++++----------------
 src/session/src/context.rs            |  6 +++++
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/src/query/src/dist_plan/merge_scan.rs b/src/query/src/dist_plan/merge_scan.rs
index 3bada2533a..c8a4ebcc77 100644
--- a/src/query/src/dist_plan/merge_scan.rs
+++ b/src/query/src/dist_plan/merge_scan.rs
@@ -41,7 +41,6 @@ use datafusion_physical_expr::EquivalenceProperties;
 use datatypes::schema::{Schema, SchemaRef};
 use futures_util::StreamExt;
 use greptime_proto::v1::region::RegionRequestHeader;
-use greptime_proto::v1::QueryContext;
 use meter_core::data::ReadItem;
 use meter_macros::read_meter;
 use session::context::QueryContextRef;
@@ -185,24 +184,25 @@ impl MergeScanExec {
         context: Arc<TaskContext>,
         partition: usize,
     ) -> Result<SendableRecordBatchStream> {
+        // prepare states to move
         let regions = self.regions.clone();
         let region_query_handler = self.region_query_handler.clone();
         let metric = MergeScanMetric::new(&self.metric);
-        let schema = Self::arrow_schema_to_schema(self.schema())?;
-
-        let dbname = context.task_id().unwrap_or_default();
-        let tracing_context = TracingContext::from_json(context.session_id().as_str());
-        let current_catalog = self.query_ctx.current_catalog().to_string();
-        let current_schema = self.query_ctx.current_schema().to_string();
-        let current_channel = self.query_ctx.channel();
-        let timezone = self.query_ctx.timezone().to_string();
-        let extensions = self.query_ctx.extensions();
-        let target_partition = self.target_partition;
-
+        let schema = self.schema.clone();
+        let query_ctx = self.query_ctx.clone();
         let sub_stage_metrics_moved = self.sub_stage_metrics.clone();
         let plan = self.plan.clone();
+        let target_partition = self.target_partition;
+        let dbname = context.task_id().unwrap_or_default();
+        let tracing_context = TracingContext::from_json(context.session_id().as_str());
+        let current_channel = self.query_ctx.channel();
+
         let stream = Box::pin(stream!({
-            MERGE_SCAN_REGIONS.observe(regions.len() as f64);
+            // only report metrics once for each MergeScan
+            if partition == 0 {
+                MERGE_SCAN_REGIONS.observe(regions.len() as f64);
+            }
+
             let _finish_timer = metric.finish_time().timer();
             let mut ready_timer = metric.ready_time().timer();
             let mut first_consume_timer = Some(metric.first_consume_time().timer());
@@ -217,13 +217,7 @@ impl MergeScanExec {
                     header: Some(RegionRequestHeader {
                         tracing_context: tracing_context.to_w3c(),
                         dbname: dbname.clone(),
-                        query_context: Some(QueryContext {
-                            current_catalog: current_catalog.clone(),
-                            current_schema: current_schema.clone(),
-                            timezone: timezone.clone(),
-                            extensions: extensions.clone(),
-                            channel: current_channel as u32,
-                        }),
+                        query_context: Some(query_ctx.as_ref().into()),
                     }),
                     region_id,
                     plan: plan.clone(),
diff --git a/src/session/src/context.rs b/src/session/src/context.rs
index 15ea0a8baf..28ecca6a3f 100644
--- a/src/session/src/context.rs
+++ b/src/session/src/context.rs
@@ -137,6 +137,12 @@ impl From<QueryContext> for api::v1::QueryContext {
     }
 }
 
+impl From<&QueryContext> for api::v1::QueryContext {
+    fn from(ctx: &QueryContext) -> Self {
+        ctx.clone().into()
+    }
+}
+
 impl QueryContext {
     pub fn arc() -> QueryContextRef {
         Arc::new(QueryContextBuilder::default().build())