fix(cubesql): Metabase - substring __user (#5328)

rust/cubesql/cubesql/src/compile/mod.rs

@@ -10907,6 +10907,37 @@ ORDER BY \"COUNT(count)\" DESC"
         )
     }
 
+    #[tokio::test]
+    async fn test_metabase_substring_user() {
+        init_logger();
+
+        let logical_plan = convert_select_to_query_plan(
+            "SELECT \"source\".\"substring131715\" AS \"substring131715\" 
+                FROM (
+                    SELECT 
+                        \"public\".\"KibanaSampleDataEcommerce\".\"__user\" AS \"__user\", 
+                        SUBSTRING(\"public\".\"KibanaSampleDataEcommerce\".\"__user\" FROM 1 FOR 1234) AS \"substring131715\" 
+                    FROM \"public\".\"KibanaSampleDataEcommerce\"
+                ) AS \"source\" 
+                LIMIT 10000".to_string(),
+            DatabaseProtocol::PostgreSQL
+        ).await.as_logical_plan();
+
+        assert_eq!(
+            logical_plan.find_cube_scan().request,
+            V1LoadRequestQuery {
+                measures: Some(vec![]),
+                dimensions: Some(vec![]),
+                segments: Some(vec![]),
+                time_dimensions: None,
+                order: None,
+                limit: Some(10000),
+                offset: None,
+                filters: None,
+            }
+        )
+    }
+
     #[tokio::test]
     async fn test_select_asterisk_cross_join() {
         init_logger();

rust/cubesql/cubesql/src/compile/rewrite/cost.rs

@@ -72,6 +72,7 @@ impl CostFunction<LogicalPlanLanguage> for BestCubePlan {
         let cube_members = match enode {
             LogicalPlanLanguage::Measure(_) => 1,
             LogicalPlanLanguage::Dimension(_) => 1,
+            LogicalPlanLanguage::ChangeUser(_) => 1,
             LogicalPlanLanguage::LiteralMember(_) => 1,
             LogicalPlanLanguage::TimeDimensionGranularity(TimeDimensionGranularity(Some(_))) => 1,
             LogicalPlanLanguage::MemberError(_) => 1,