fix: empty query during failed transaction with parser off

integration/rust/tests/integration/empty_query.rs

@@ -0,0 +1,65 @@
+use anyhow::{Context, Result, ensure};
+use serial_test::serial;
+use tokio_postgres::{SimpleQueryMessage, error::SqlState};
+
+use crate::setup::{admin_tokio, connections_tokio};
+
+#[tokio::test]
+#[serial]
+async fn empty_query_then_rollback_parser_on() -> Result<()> {
+    check_empty_query_then_rollback("on").await
+}
+
+#[tokio::test]
+#[serial]
+async fn empty_query_then_rollback_parser_auto() -> Result<()> {
+    check_empty_query_then_rollback("auto").await
+}
+
+#[tokio::test]
+#[serial]
+async fn empty_query_then_rollback_parser_off() -> Result<()> {
+    check_empty_query_then_rollback("off").await
+}
+
+async fn check_empty_query_then_rollback(level: &str) -> Result<()> {
+    let admin = admin_tokio().await;
+    admin
+        .batch_execute(&format!("SET query_parser TO '{level}'"))
+        .await?;
+
+    let result = async {
+        let clients = connections_tokio().await;
+        let client = &clients[0];
+        client.batch_execute("BEGIN").await?;
+        let error = client
+            .simple_query("SELECT 1/0")
+            .await
+            .err()
+            .context("division by zero must fail")?;
+        ensure!(error.code() == Some(&SqlState::DIVISION_BY_ZERO));
+
+        let messages = client.simple_query(";").await?;
+        // tokio-postgres exposes EmptyQueryResponse as CommandComplete(0).
+        ensure!(matches!(
+            messages.as_slice(),
+            [SimpleQueryMessage::CommandComplete(0)]
+        ));
+
+        // An empty query must not clear the failed transaction state.
+        let error = client
+            .simple_query("SELECT 1")
+            .await
+            .err()
+            .context("query in failed transaction must fail")?;
+        ensure!(error.code() == Some(&SqlState::IN_FAILED_SQL_TRANSACTION));
+
+        client.batch_execute("ROLLBACK").await?;
+        client.simple_query("SELECT 1").await?;
+        Ok(())
+    }
+    .await;
+
+    admin.batch_execute("RELOAD").await?;
+    result
+}

integration/rust/tests/integration/mod.rs

@@ -15,6 +15,7 @@ pub mod cross_shard_disabled;
 mod cross_shard_oid_drift;
 mod cross_shard_omni_check;
 pub mod distinct;
+mod empty_query;
 pub mod explain;
 pub mod fake_transactions;
 pub mod having;

pgdog/src/frontend/client/query_engine/query.rs

@@ -573,7 +573,7 @@ impl QueryEngine {
             && client_request
                 .ast
                 .as_ref()
-                .is_none_or(|ast| ast.ast.stmts().next().is_some())
+                .is_some_and(|ast| ast.ast.stmts().next().is_some())
         {
             let error = ErrorResponse::in_failed_transaction();
 

pgdog/src/frontend/client/query_engine/test/mod.rs

@@ -35,7 +35,6 @@ mod pub_sub;
 mod regression_auto_two_pc;
 mod regression_bind_transaction_end;
 mod regression_flush_error;
-mod regression_parser_off_rollback;
 mod regression_pinned_portal;
 mod regression_pinned_sync;
 mod regression_prepare_transaction_end;