fix: LIMIT without ORDER BY did not work for cross-shard queries

integration/rust/tests/integration/limit.rs

@@ -2,6 +2,41 @@ use crate::setup::admin_sqlx;
 use crate::setup::connections_sqlx;
 use sqlx::{Executor, Row, postgres::PgPool};
 
+#[tokio::test]
+async fn limit_without_order_by_across_shards() -> Result<(), Box<dyn std::error::Error>> {
+    let pools = connections_sqlx().await;
+    let mut transaction = pools[1].begin().await?;
+
+    transaction.execute("TRUNCATE sharded").await?;
+    // Guarantee five rows on each shard so a per-shard LIMIT exceeds the global limit.
+    for shard in [0, 1] {
+        transaction
+            .execute(
+                format!(
+                    "/* pgdog_shard: {shard} */ INSERT INTO sharded (id) VALUES (1), (2), (3), (4), (5)"
+                )
+                .as_str(),
+            )
+            .await?;
+    }
+
+    for (limit, expected) in [(5_i64, 5), (0, 0), (100, 10)] {
+        let rows = sqlx::raw_sql(&format!("SELECT id FROM sharded LIMIT {limit}"))
+            .fetch_all(&mut *transaction)
+            .await?;
+        assert_eq!(rows.len(), expected, "simple protocol LIMIT {limit}");
+
+        let rows = sqlx::query("SELECT id FROM sharded LIMIT $1")
+            .bind(limit)
+            .fetch_all(&mut *transaction)
+            .await?;
+        assert_eq!(rows.len(), expected, "extended protocol LIMIT {limit}");
+    }
+
+    transaction.rollback().await?;
+    Ok(())
+}
+
 #[tokio::test]
 async fn limit_across_shards() -> Result<(), Box<dyn std::error::Error>> {
     let sharded = connections_sqlx().await.get(1).cloned().unwrap();

pgdog/src/frontend/router/parser/route.rs

@@ -333,6 +333,7 @@ impl Route {
         !self.order_by().is_empty()
             || !self.aggregate().is_empty()
             || self.distinct().is_some()
+            || self.limit().limit.is_some()
             || self.limit().offset.is_some()
     }
 
@@ -741,7 +742,7 @@ mod test {
             },
             None,
         );
-        assert!(!route.requires_post_processing());
+        assert!(route.requires_post_processing());
     }
 
     #[test]