fix(navicat): clarify stateless tunnel transaction errors (#13073)

* fix(navicat): allow backup transactions through HTTP tunnel

* style(navicat): format tunnel source for CI

* style(navicat): match CI rustfmt output

* fix(transfer): complete Oracle transfer test request

* Revert "fix(navicat): allow backup transactions through HTTP tunnel"

This reverts commit ed147aced7.

* fix(navicat): clarify stateless transaction boundary

crates/dbx-driver-support/src/navicat_mysql_tunnel.rs

@@ -289,7 +289,7 @@ fn validate_stateless_query(sql: &str) -> Result<(), String> {
                     }));
         if transaction {
             return Err(
-                "Transactions and autocommit settings are not supported by Navicat HTTP tunnels: each request uses a separate MySQL session"
+                "Transactions, autocommit settings, and consistent snapshots are not supported by the stateless Navicat HTTP tunnel; use the DBX TCP HTTP tunnel (dbx_tunnel.php) for a fixed database session"
                     .to_string(),
             );
         }
@@ -684,7 +684,9 @@ mod tests {
             let response = send_test_command(&mut client, 0x03, sql.as_bytes()).await;
             assert_eq!(response[0], 0xff, "{sql}");
             assert_eq!(u16::from_le_bytes(response[1..3].try_into().unwrap()), 1235, "{sql}");
-            assert!(String::from_utf8_lossy(&response[9..]).contains("separate MySQL session"));
+            let message = String::from_utf8_lossy(&response[9..]);
+            assert!(message.contains("stateless Navicat HTTP tunnel"), "{sql}: {message}");
+            assert!(message.contains("fixed database session"), "{sql}: {message}");
         }
         assert!(tokio::time::timeout(std::time::Duration::from_millis(50), http_listener.accept()).await.is_err());
         assert_eq!(send_test_command(&mut client, 0x0e, b"").await[0], 0);

deploy/NAVICAT_HTTP_TUNNEL.md

@@ -23,6 +23,14 @@ can change a POST request into a GET.
 
 This protocol supports regular queries, `USE`, ping, and disconnect. MySQL TLS
 and prepared statements are not supported by the Navicat HTTP tunnel protocol.
-Each HTTP request opens a separate MySQL session. Transactions (including manual
-transactions and consistent backup snapshots), savepoints, and autocommit
-settings are rejected before any SQL is sent to the PHP host.
+Each HTTP request opens a separate MySQL session, so this endpoint is appropriate
+only for non-transactional operations and backups that do not request a consistent
+snapshot. Transactions, savepoints, autocommit settings, and consistent-snapshot
+backup sequences are rejected before any SQL is sent to the PHP host; this prevents
+a successful-looking `ROLLBACK` from failing to undo a write that ran in another
+session.
+
+For transaction workflows or backups that require a consistent snapshot, deploy
+DBX's own `deploy/dbx_tunnel.php` endpoint instead. That endpoint keeps one
+database TCP session alive for the lifetime of the tunnel and is configured as the
+DBX TCP HTTP tunnel, not as the Navicat-compatible endpoint.