refactor: per review

Author: discord9

src/datatypes/src/schema/column_schema.rs

@@ -292,6 +292,7 @@ impl ColumnSchema {
     }
 
     /// Creates an impure default value for this column, only if it have a impure default constraint.
+    /// Otherwise, returns `Ok(None)`.
     pub fn create_impure_default(&self) -> Result<Option<Value>> {
         match &self.default_constraint {
             Some(c) => c.create_impure_default(&self.data_type),

src/flow/src/adapter/util.rs

@@ -164,10 +164,7 @@ pub fn table_info_value_to_relation_desc(
         .map(|c| c.default_constraint().cloned())
         .collect_vec();
 
-    Ok(TableDesc {
-        relation_desc,
-        default_values,
-    })
+    Ok(TableDesc::new(relation_desc, default_values))
 }
 
 pub fn from_proto_to_data_type(

src/operator/src/req_convert/insert/fill_impure_default.rs

@@ -53,15 +53,17 @@ impl ImpureDefaultFiller {
         for column in impure_column_list {
             let default_value = column
                 .create_impure_default()
-                .context(ConvertColumnDefaultConstraintSnafu {
+                .with_context(|_| ConvertColumnDefaultConstraintSnafu {
                     column_name: column.name.clone(),
                 })?
-                .expect("impure default value");
-            let grpc_default_value = api::helper::to_proto_value(default_value.clone());
-            let def = column_schemas_to_defs(vec![column], &pk_names)?
-                .into_iter()
-                .next()
-                .expect("column def have one element");
+                .with_context(|| UnexpectedSnafu {
+                    violated: format!(
+                        "Expect default value to be impure, found {:?}",
+                        column.default_constraint()
+                    ),
+                })?;
+            let grpc_default_value = api::helper::to_proto_value(default_value);
+            let def = column_schemas_to_defs(vec![column], &pk_names)?.swap_remove(0);
             let grpc_column_schema = api::v1::ColumnSchema {
                 column_name: def.name,
                 datatype: def.data_type,