Fixes division by zero bug by returning NAN for divisions by zero? (#4402)

Co-authored-by: Emmanuel Keller <emmanuel.keller@surrealdb.com>

core/src/dbs/group.rs

@@ -329,7 +329,7 @@ impl Aggregator {
 			OptimisedAggregate::MathSum => self.math_sum.take().unwrap_or(Value::None),
 			OptimisedAggregate::MathMean => {
 				if let Some((v, i)) = self.math_mean.take() {
-					v.try_div(i.into())?
+					v.try_div(i.into()).unwrap_or(f64::NAN.into())
 				} else {
 					Value::None
 				}

core/src/fnc/operate.rs

@@ -57,7 +57,7 @@ pub fn mul(a: Value, b: Value) -> Result<Value, Error> {
 }
 
 pub fn div(a: Value, b: Value) -> Result<Value, Error> {
-	a.try_div(b)
+	Ok(a.try_div(b).unwrap_or(f64::NAN.into()))
 }
 
 pub fn rem(a: Value, b: Value) -> Result<Value, Error> {

lib/tests/group.rs

@@ -674,3 +674,63 @@ async fn select_array_count_subquery_group_by() -> Result<(), Error> {
 	//
 	Ok(())
 }
+
+#[tokio::test]
+async fn select_aggregate_mean_update() -> Result<(), Error> {
+	let sql = "
+		CREATE test:a SET a = 3;
+		DEFINE TABLE foo AS SELECT
+			math::mean(a) AS avg
+		FROM test
+		GROUP ALL;
+
+		UPDATE test:a SET a = 2;
+
+		SELECT avg FROM foo;
+	";
+	let dbs = new_ds().await?;
+	let ses = Session::owner().with_ns("test").with_db("test");
+	let res = &mut dbs.execute(sql, &ses, None).await?;
+	assert_eq!(res.len(), 4);
+	//
+	let tmp = res.remove(0).result?;
+	let val = Value::parse(
+		"[
+		{
+			id: test:a,
+			a: 3
+		}
+	]",
+	);
+
+	assert_eq!(tmp, val);
+	//
+	let tmp = res.remove(0).result?;
+	let val = Value::parse("None");
+
+	assert_eq!(tmp, val);
+
+	let tmp = res.remove(0).result?;
+	let val = Value::parse(
+		"[
+			{
+				id: test:a,
+				a: 2
+			}
+		]",
+	);
+
+	assert_eq!(tmp, val);
+
+	let tmp = res.remove(0).result?;
+	let val = Value::parse(
+		"[
+			{
+				avg: 2
+			}
+		]",
+	);
+	assert_eq!(tmp, val);
+
+	Ok(())
+}