fix: the first resp may not contain schema. (#366)

core/src/response.rs

@@ -45,7 +45,7 @@ pub struct ProgressValues {
     pub bytes: usize,
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct SchemaField {
     pub name: String,
     #[serde(rename = "type")]

driver/src/rest_api.rs

@@ -71,6 +71,7 @@ impl Connection for RestAPIConnection {
     async fn query_iter_ext(&self, sql: &str) -> Result<RowStatsIterator> {
         info!("query iter ext: {}", sql);
         let resp = self.client.start_query(sql).await?;
+        let resp = self.wait_for_schema(resp).await?;
         let (schema, rows) = RestAPIRows::from_response(self.client.clone(), resp)?;
         Ok(RowStatsIterator::new(Arc::new(schema), Box::pin(rows)))
     }
@@ -199,16 +200,33 @@ impl<'o> RestAPIConnection {
         if !pre.data.is_empty() {
             return Ok(pre);
         }
+        // preserve schema since it is not included in the final response in old servers
+        let pre_schema = pre.schema.clone();
         let mut result = pre;
-        // preserve schema since it is no included in the final response
-        let schema = result.schema;
         while let Some(next_uri) = result.next_uri {
             result = self.client.query_page(&result.id, &next_uri).await?;
             if !result.data.is_empty() {
                 break;
             }
         }
-        result.schema = schema;
+        if result.schema.is_empty() {
+            result.schema = pre_schema;
+        }
+        Ok(result)
+    }
+
+    async fn wait_for_schema(&self, pre: QueryResponse) -> Result<QueryResponse> {
+        if !pre.data.is_empty() || !pre.schema.is_empty() {
+            return Ok(pre);
+        }
+        let mut result = pre;
+        // preserve schema since it is no included in the final response
+        while let Some(next_uri) = result.next_uri {
+            result = self.client.query_page(&result.id, &next_uri).await?;
+            if !result.data.is_empty() || !result.schema.is_empty() {
+                break;
+            }
+        }
         Ok(result)
     }