fix: return empty when promql gets non-exist label name (#7899)

* fix: return empty when promql gets non-exist label name

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: fmt

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: minor refactor

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: typo

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

---------

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

src/catalog/src/process_manager.rs

@@ -395,7 +395,7 @@ impl SlowQueryTimer {
 
 impl Drop for SlowQueryTimer {
     fn drop(&mut self) {
-        // Calculate the elaspsed duration since the timer is created.
+        // Calculate the elapsed duration since the timer is created.
         let elapsed = self.start.elapsed();
         if elapsed > self.threshold {
             // Only capture a portion of slow queries based on sample_ratio.

src/frontend/src/instance/promql.rs

@@ -31,7 +31,7 @@ use snafu::{OptionExt, ResultExt};
 use crate::error::{
     CatalogSnafu, CollectRecordbatchSnafu, ExecLogicalPlanSnafu,
     PrometheusLabelValuesQueryPlanSnafu, PrometheusMetricNamesQueryPlanSnafu, ReadTableSnafu,
-    Result, TableNotFoundSnafu,
+    Result, TableNotFoundSnafu, TableSnafu,
 };
 use crate::instance::Instance;
 
@@ -120,20 +120,32 @@ impl Instance {
             })
             .unwrap_or_else(|| ctx.current_schema());
 
+        let full_table_name = format_full_table_name(ctx.current_catalog(), &table_schema, &metric);
         let table = self
             .catalog_manager
             .table(ctx.current_catalog(), &table_schema, &metric, Some(ctx))
             .await
             .context(CatalogSnafu)?
             .with_context(|| TableNotFoundSnafu {
-                table_name: format_full_table_name(ctx.current_catalog(), &table_schema, &metric),
+                table_name: full_table_name.clone(),
             })?;
 
+        // Check label column existence before building the query plan so a missing label can be
+        // reported as `TableColumnNotFound` and handled like Prometheus expects.
+        if table.schema().column_schema_by_name(&label_name).is_none() {
+            return table::error::ColumnNotExistsSnafu {
+                column_name: label_name,
+                table_name: full_table_name,
+            }
+            .fail()
+            .context(TableSnafu);
+        }
+
         let dataframe = self
             .query_engine
             .read_table(table.clone())
             .with_context(|_| ReadTableSnafu {
-                table_name: format_full_table_name(ctx.current_catalog(), &table_schema, &metric),
+                table_name: full_table_name,
             })?;
 
         let scan_plan = dataframe.into_unoptimized_plan();

tests-integration/tests/http.rs

@@ -1176,6 +1176,20 @@ pub async fn test_prom_http_api(store_type: StorageType) {
         .await;
     assert_eq!(res.status(), StatusCode::OK);
 
+    // query non-exist label in metric table
+    let res = client
+        .get("/v1/prometheus/api/v1/label/not_exist_label/values?match[]=demo&start=0&end=600")
+        .send()
+        .await;
+    assert_eq!(res.status(), StatusCode::OK);
+    let prom_resp = res.json::<PrometheusJsonResponse>().await;
+    assert_eq!(prom_resp.status, "success");
+    assert!(prom_resp.error.is_none() && prom_resp.error_type.is_none());
+    assert_eq!(
+        prom_resp.data,
+        serde_json::from_value::<PrometheusResponse>(json!([])).unwrap()
+    );
+
     // query `__name__` without match[]
     // create a physical table and a logical table
     let res = client