From 2c9c9f872aac896d980a8284ee6e8a3dab8d6d73 Mon Sep 17 00:00:00 2001
From: Karen Chen <64801825+karenc-bq@users.noreply.github.com>
Date: Tue, 6 Jan 2026 09:10:47 -0800
Subject: [PATCH] fix: mysql's event listeners should be removed from
 `clientWrapper.client.connection` not `clientWrapper.client` and ensure the
 same error listener is not attached multiple times

---
 mysql/lib/mysql_error_handler.ts    | 21 ++++++++++++++-------
 pg/lib/abstract_pg_error_handler.ts | 11 +++++++++--
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/mysql/lib/mysql_error_handler.ts b/mysql/lib/mysql_error_handler.ts
index 69d23e1e0..45066735c 100644
--- a/mysql/lib/mysql_error_handler.ts
+++ b/mysql/lib/mysql_error_handler.ts
@@ -24,6 +24,8 @@ export class MySQLErrorHandler implements ErrorHandler {
   private unexpectedError: Error | null = null;
   protected static readonly SYNTAX_ERROR_CODES = ["42000", "42S02"];
   protected static readonly SYNTAX_ERROR_MESSAGE = "You have an error in your SQL syntax";
+  protected isNoOpListenerAttached = false;
+  protected isTrackingListenerAttached = false;
 
   protected noOpListener(error: any) {
     // Ignore the received error.
@@ -80,20 +82,24 @@ export class MySQLErrorHandler implements ErrorHandler {
   }
 
   attachErrorListener(clientWrapper: ClientWrapper | undefined): void {
-    if (!clientWrapper || !clientWrapper.client) {
+    if (!clientWrapper || !clientWrapper.client || this.isTrackingListenerAttached) {
       return;
     }
     this.unexpectedError = null;
-    clientWrapper.client.removeListener("error", this.noOpListener);
-    clientWrapper.client.on("error", this.trackingListener);
+    clientWrapper.client.connection.removeListener("error", this.noOpListener);
+    this.isNoOpListenerAttached = false;
+    clientWrapper.client.connection.on("error", this.trackingListener);
+    this.isTrackingListenerAttached = true;
   }
 
   attachNoOpErrorListener(clientWrapper: ClientWrapper | undefined): void {
-    if (!clientWrapper || !clientWrapper.client) {
+    if (!clientWrapper || !clientWrapper.client || this.isNoOpListenerAttached) {
       return;
     }
-    clientWrapper.client.removeListener("error", this.trackingListener);
-    clientWrapper.client.on("error", this.noOpListener);
+    clientWrapper.client.connection.removeListener("error", this.trackingListener);
+    this.isTrackingListenerAttached = false;
+    clientWrapper.client.connection.on("error", this.noOpListener);
+    this.isNoOpListenerAttached = true;
   }
 
   removeErrorListener(clientWrapper: ClientWrapper | undefined): void {
@@ -101,6 +107,7 @@ export class MySQLErrorHandler implements ErrorHandler {
       return;
     }
 
-    clientWrapper.client.removeListener("error", this.trackingListener);
+    clientWrapper.client.connection.removeListener("error", this.trackingListener);
+    this.isTrackingListenerAttached = false;
   }
 }
diff --git a/pg/lib/abstract_pg_error_handler.ts b/pg/lib/abstract_pg_error_handler.ts
index cefa2b7db..9a5799c00 100644
--- a/pg/lib/abstract_pg_error_handler.ts
+++ b/pg/lib/abstract_pg_error_handler.ts
@@ -24,6 +24,8 @@ export abstract class AbstractPgErrorHandler implements ErrorHandler {
   protected unexpectedError: Error | null = null;
   protected static readonly SYNTAX_ERROR_CODE = "42601";
   protected static readonly SYNTAX_ERROR_MESSAGE = "syntax error";
+  protected isNoOpListenerAttached = false;
+  protected isTrackingListenerAttached = false;
 
   abstract getNetworkErrors(): string[];
 
@@ -84,20 +86,24 @@ export abstract class AbstractPgErrorHandler implements ErrorHandler {
   }
 
   attachErrorListener(clientWrapper: ClientWrapper | undefined): void {
-    if (!clientWrapper || !clientWrapper.client) {
+    if (!clientWrapper || !clientWrapper.client || this.isTrackingListenerAttached) {
       return;
     }
     this.unexpectedError = null;
     clientWrapper.client.removeListener("error", this.noOpListener);
+    this.isNoOpListenerAttached = false;
     clientWrapper.client.on("error", this.trackingListener);
+    this.isTrackingListenerAttached = true;
   }
 
   attachNoOpErrorListener(clientWrapper: ClientWrapper | undefined): void {
-    if (!clientWrapper || !clientWrapper.client) {
+    if (!clientWrapper || !clientWrapper.client || this.isNoOpListenerAttached) {
       return;
     }
     clientWrapper.client.removeListener("error", this.trackingListener);
+    this.isTrackingListenerAttached = false;
     clientWrapper.client.on("error", this.noOpListener);
+    this.isNoOpListenerAttached = true;
   }
 
   removeErrorListener(clientWrapper: ClientWrapper | undefined): void {
@@ -106,5 +112,6 @@ export abstract class AbstractPgErrorHandler implements ErrorHandler {
     }
 
     clientWrapper.client.removeListener("error", this.trackingListener);
+    this.isTrackingListenerAttached = false;
   }
 }