fix(cubesql): Support GROUP BY () empty grouping set

rust/cubesql/cubesql/Cargo.toml

@@ -10,7 +10,7 @@ homepage = "https://cube.dev"
 
 [dependencies]
 arc-swap = "1"
-datafusion = { git = 'https://github.com/cube-js/arrow-datafusion.git', rev = "d203d8771a9673fb676b44dce1f99e91634b4080", default-features = false, features = [
+datafusion = { git = 'https://github.com/cube-js/arrow-datafusion.git', rev = "ee20ad38796f4a9966ff58b9ace425c7488459e9", default-features = false, features = [
     "regex_expressions",
     "unicode_expressions",
 ] }

rust/cubesql/cubesql/src/compile/test/test_cube_scan.rs

@@ -1,4 +1,4 @@
-use cubeclient::models::V1LoadRequestQuery;
+use cubeclient::models::{V1LoadRequestQuery, V1LoadRequestQueryFilterItem};
 use pretty_assertions::assert_eq;
 
 use crate::compile::{
@@ -224,3 +224,49 @@ async fn cubescan_limit_offset_limit_offset() {
         );
     }
 }
+
+/// GROUP BY () is an empty grouping set, equivalent to aggregation without GROUP BY
+#[tokio::test]
+async fn cubescan_empty_group_by_tuple() {
+    init_testing_logger();
+
+    let query_plan = convert_select_to_query_plan(
+        // language=PostgreSQL
+        r#"
+        SELECT
+            MEASURE(count),
+            MEASURE(maxPrice)
+        FROM
+            KibanaSampleDataEcommerce
+        WHERE customer_gender = 'female'
+        GROUP BY ()
+        LIMIT 100
+        "#
+        .to_string(),
+        DatabaseProtocol::PostgreSQL,
+    )
+    .await;
+
+    let logical_plan = query_plan.as_logical_plan();
+    assert_eq!(
+        logical_plan.find_cube_scan().request,
+        V1LoadRequestQuery {
+            measures: Some(vec![
+                "KibanaSampleDataEcommerce.count".to_string(),
+                "KibanaSampleDataEcommerce.maxPrice".to_string(),
+            ]),
+            dimensions: Some(vec![]),
+            segments: Some(vec![]),
+            order: Some(vec![]),
+            limit: Some(100),
+            filters: Some(vec![V1LoadRequestQueryFilterItem {
+                member: Some("KibanaSampleDataEcommerce.customer_gender".to_string()),
+                operator: Some("equals".to_string()),
+                values: Some(vec!["female".to_string()]),
+                or: None,
+                and: None,
+            }]),
+            ..Default::default()
+        }
+    );
+}