refactor(executor): use plan node to infer column name

src/array/data_chunk.rs

@@ -108,6 +108,8 @@ impl DataChunk {
         self.arrays.iter().map(|a| a.get_estimated_size()).sum()
     }
 
+    /// This function should only be called in plan nodes. If you want to change column name, you
+    /// should change the plan node, instead of directly attaching a header to the chunk.
     pub fn set_header(&mut self, header: Vec<String>) {
         self.header = Some(header);
     }

src/executor/create.rs

@@ -24,8 +24,7 @@ impl<S: Storage> CreateTableExecutor<S> {
             )
             .await?;
 
-        let mut chunk = DataChunk::single(0);
-        chunk.set_header(vec!["$create".to_string()]);
+        let chunk = DataChunk::single(0);
         yield chunk
     }
 }

src/optimizer/plan_nodes/logical_create_table.rs

@@ -7,7 +7,7 @@ use serde::Serialize;
 
 use super::*;
 use crate::catalog::ColumnCatalog;
-use crate::types::{DatabaseId, SchemaId};
+use crate::types::{DataTypeKind, DatabaseId, SchemaId};
 
 /// The logical plan of `CREATE TABLE`.
 #[derive(Debug, Clone, Serialize)]
@@ -54,8 +54,18 @@ impl LogicalCreateTable {
     }
 }
 impl PlanTreeNodeLeaf for LogicalCreateTable {}
+
 impl_plan_tree_node_for_leaf!(LogicalCreateTable);
-impl PlanNode for LogicalCreateTable {}
+
+impl PlanNode for LogicalCreateTable {
+    fn schema(&self) -> Vec<ColumnDesc> {
+        vec![ColumnDesc::new(
+            DataType::new(DataTypeKind::Int(None), false),
+            "$create".to_string(),
+            false,
+        )]
+    }
+}
 
 impl fmt::Display for LogicalCreateTable {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

src/optimizer/plan_nodes/physical_create_table.rs

@@ -27,7 +27,11 @@ impl PhysicalCreateTable {
 impl PlanTreeNodeLeaf for PhysicalCreateTable {}
 impl_plan_tree_node_for_leaf!(PhysicalCreateTable);
 
-impl PlanNode for PhysicalCreateTable {}
+impl PlanNode for PhysicalCreateTable {
+    fn schema(&self) -> Vec<ColumnDesc> {
+        self.logical.schema()
+    }
+}
 
 impl fmt::Display for PhysicalCreateTable {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {