From e683da2db6194ba93f5721e1d5556f6c6e5f5216 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 25 Mar 2026 16:42:23 +0300
Subject: [PATCH] db.mysql: fix real_query to return proper mysql error (fixes
 #18059)

---
 vlib/db/mysql/mysql.c.v            | 11 +++--
 vlib/db/mysql/prepared_stmt_test.v | 67 ++++++++++++++++++++++++++++++
 vlib/db/mysql/stmt.c.v             | 18 ++++++--
 vlib/db/mysql/utils.c.v            | 10 +++++
 4 files changed, 100 insertions(+), 6 deletions(-)

diff --git a/vlib/db/mysql/mysql.c.v b/vlib/db/mysql/mysql.c.v
index f0cb5d18f..b3dcfc730 100644
--- a/vlib/db/mysql/mysql.c.v
+++ b/vlib/db/mysql/mysql.c.v
@@ -513,7 +513,7 @@ pub fn (db &DB) prepare(query string) !StmtHandle {
 
 	mut code := C.mysql_stmt_prepare(stmt, query.str, query.len)
 	if code != 0 {
-		db.throw_mysql_error()!
+		throw_mysql_stmt_error(stmt)!
 	}
 
 	return StmtHandle{
@@ -543,12 +543,12 @@ pub fn (stmt &StmtHandle) execute(params []string) ![]Row {
 
 	mut response := C.mysql_stmt_bind_param(stmt.stmt, unsafe { &C.MYSQL_BIND(bind_params.data) })
 	if response == true {
-		stmt.db.throw_mysql_error()!
+		throw_mysql_stmt_error(stmt.stmt)!
 	}
 
 	mut code := C.mysql_stmt_execute(stmt.stmt)
 	if code != 0 {
-		stmt.db.throw_mysql_error()!
+		throw_mysql_stmt_error(stmt.stmt)!
 	}
 
 	query_metadata := C.mysql_stmt_result_metadata(stmt.stmt)
@@ -610,6 +610,11 @@ fn (db &DB) throw_mysql_error() ! {
 	return error_with_code(get_error_msg(db.conn), get_errno(db.conn))
 }
 
+@[inline]
+fn throw_mysql_stmt_error(stmt &C.MYSQL_STMT) ! {
+	return error_with_code(get_stmt_error_msg(stmt), get_stmt_errno(stmt))
+}
+
 @[inline]
 fn (db &DB) check_connection_is_established() ! {
 	if isnil(db.conn) {
diff --git a/vlib/db/mysql/prepared_stmt_test.v b/vlib/db/mysql/prepared_stmt_test.v
index 67949e68d..4ce0f06b8 100644
--- a/vlib/db/mysql/prepared_stmt_test.v
+++ b/vlib/db/mysql/prepared_stmt_test.v
@@ -100,3 +100,70 @@ fn test_stmt_bind_result_buffer_without_bind_res() {
 	second_fetch := stmt.fetch_stmt()!
 	assert second_fetch == 100
 }
+
+fn test_stmt_prepare_returns_mysql_error_code() {
+	$if !network ? {
+		eprintln('> Skipping test ${@FN}, since `-d network` is not passed.')
+		eprintln('> This test requires a working mysql server running on localhost.')
+		return
+	}
+	config := mysql.Config{
+		host:     '127.0.0.1'
+		port:     3306
+		username: 'root'
+		password: ''
+		dbname:   'mysql'
+	}
+
+	mut db := mysql.connect(config)!
+	defer {
+		db.close() or {}
+	}
+
+	mut stmt := db.init_stmt('insert into missing_stmt_errno_test (value) values (?)')
+	defer {
+		stmt.close() or {}
+	}
+	stmt.prepare() or {
+		assert err.code() == 1146
+		return
+	}
+	assert false
+}
+
+fn test_prepare_execute_returns_mysql_error_code() {
+	$if !network ? {
+		eprintln('> Skipping test ${@FN}, since `-d network` is not passed.')
+		eprintln('> This test requires a working mysql server running on localhost.')
+		return
+	}
+	config := mysql.Config{
+		host:     '127.0.0.1'
+		port:     3306
+		username: 'root'
+		password: ''
+		dbname:   'mysql'
+	}
+
+	mut db := mysql.connect(config)!
+	defer {
+		db.close() or {}
+	}
+
+	db.exec('drop table if exists stmt_handle_errno_test')!
+	db.exec('create table if not exists stmt_handle_errno_test (
+		id INT PRIMARY KEY AUTO_INCREMENT,
+		value VARCHAR(255) NOT NULL UNIQUE
+	)')!
+	db.exec_param('insert into stmt_handle_errno_test (value) values (?)', 'duplicate')!
+
+	stmt := db.prepare('insert into stmt_handle_errno_test (value) values (?)')!
+	defer {
+		stmt.close()
+	}
+	stmt.execute(['duplicate']) or {
+		assert err.code() == 1062
+		return
+	}
+	assert false
+}
diff --git a/vlib/db/mysql/stmt.c.v b/vlib/db/mysql/stmt.c.v
index ae2ce2082..7ec647336 100644
--- a/vlib/db/mysql/stmt.c.v
+++ b/vlib/db/mysql/stmt.c.v
@@ -53,6 +53,7 @@ fn C.mysql_stmt_execute(&C.MYSQL_STMT) i32
 fn C.mysql_stmt_close(&C.MYSQL_STMT) bool
 fn C.mysql_stmt_free_result(&C.MYSQL_STMT) bool
 fn C.mysql_stmt_error(&C.MYSQL_STMT) &char
+fn C.mysql_stmt_errno(&C.MYSQL_STMT) i32
 fn C.mysql_stmt_result_metadata(&C.MYSQL_STMT) &C.MYSQL_RES
 
 fn C.mysql_stmt_field_count(&C.MYSQL_STMT) u16
@@ -166,12 +167,23 @@ pub fn (stmt Stmt) close() ! {
 }
 
 fn (stmt Stmt) get_error_msg() string {
-	return unsafe { cstring_to_vstring(&char(C.mysql_stmt_error(stmt.stmt))) }
+	return get_stmt_error_msg(stmt.stmt)
 }
 
-// error returns a proper V error with a human readable description, given the error code returned by MySQL
-pub fn (stmt Stmt) error(code int) IError {
+fn (stmt Stmt) get_error_code() int {
+	return get_stmt_errno(stmt.stmt)
+}
+
+// error returns a proper V error with a human readable description,
+// given the fallback status code returned by the MySQL statement API.
+pub fn (stmt Stmt) error(fallback_code int) IError {
 	msg := stmt.get_error_msg()
+	stmt_code := stmt.get_error_code()
+	code := if stmt_code != 0 {
+		stmt_code
+	} else {
+		fallback_code
+	}
 
 	return &SQLError{
 		msg:  '${msg} (${code}) (${stmt.query})'
diff --git a/vlib/db/mysql/utils.c.v b/vlib/db/mysql/utils.c.v
index 319927a0d..ea48daa3b 100644
--- a/vlib/db/mysql/utils.c.v
+++ b/vlib/db/mysql/utils.c.v
@@ -10,6 +10,16 @@ fn get_errno(conn &C.MYSQL) int {
 	return C.mysql_errno(conn)
 }
 
+// get_stmt_error_msg returns error message from a MySQL statement instance.
+fn get_stmt_error_msg(stmt &C.MYSQL_STMT) string {
+	return unsafe { cstring_to_vstring(&char(C.mysql_stmt_error(stmt))) }
+}
+
+// get_stmt_errno returns error number from a MySQL statement instance.
+fn get_stmt_errno(stmt &C.MYSQL_STMT) int {
+	return C.mysql_stmt_errno(stmt)
+}
+
 // resolve_nil_str returns an empty string if passed value is a nil pointer.
 fn resolve_nil_str(ptr &u8) string {
 	if isnil(ptr) {
-- 
2.39.5