Rename a couple of variables

End prometheus stats with a new line separator

According to the [OpenMetrics specification](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#overall-structure), each line MUST end with `\n`. Previously, the last line was not ending with `\n`, so that strict parsers had issues reading the Prometheus stats.

src/prometheus.rs

@@ -309,6 +309,7 @@ async fn prometheus_stats(
             push_pool_stats(&mut lines);
             push_server_stats(&mut lines);
             push_database_stats(&mut lines);
+            lines.push("".to_string()); // Ensure to end the stats with a line terminator as required by the specification.
 
             Response::builder()
                 .header("content-type", "text/plain; version=0.0.4")

src/query_router.rs

@@ -386,6 +386,18 @@ impl QueryRouter {
         }
     }
 
+    /// Determines if a query is a mutation or not.
+    fn is_mutation_query(q: &sqlparser::ast::Query) -> bool {
+        use sqlparser::ast::*;
+
+        match q.body.as_ref() {
+            SetExpr::Insert(_) => true,
+            SetExpr::Update(_) => true,
+            SetExpr::Query(q) => Self::is_mutation_query(q),
+            _ => false,
+        }
+    }
+
     /// Try to infer which server to connect to based on the contents of the query.
     pub fn infer(&mut self, ast: &Vec<sqlparser::ast::Statement>) -> Result<(), Error> {
         if !self.pool_settings.query_parser_read_write_splitting {
@@ -428,8 +440,9 @@ impl QueryRouter {
                     };
 
                     let has_locks = !query.locks.is_empty();
+                    let has_mutation = Self::is_mutation_query(query);
 
-                    if has_locks {
+                    if has_locks || has_mutation {
                         self.active_role = Some(Role::Primary);
                     } else if !visited_write_statement {
                         // If we already visited a write statement, we should be going to the primary.
@@ -1113,6 +1126,26 @@ mod test {
         assert_eq!(qr.role(), None);
     }
 
+    #[test]
+    fn test_split_cte_queries() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+        qr.pool_settings.query_parser_read_write_splitting = true;
+        qr.pool_settings.query_parser_enabled = true;
+
+        let query = simple_query(
+            "WITH t AS (
+                SELECT id FROM users WHERE name ILIKE '%ja%'
+            )
+            UPDATE user_languages
+               SET settings = '{}'
+              FROM t WHERE t.id = user_id;",
+        );
+        let ast = qr.parse(&query).unwrap();
+        assert!(qr.infer(&ast).is_ok());
+        assert_eq!(qr.role(), Some(Role::Primary));
+    }
+
     #[test]
     fn test_infer_replica() {
         QueryRouter::setup();