MySQL: properly fix setting the character set

Commit e4bd73dc54542fe16121825c2a369b7f863e0de8 moved the
mysql_set_character_set() call above the mysql_real_connect() but that
doesn't actually work, as there's no connection to send the "SET NAMES"
statement on.

So do it in two steps: first, by setting the charset in the MYSQL
structure, then by asking the server to match.

Task-number: QTBUG-55444
Change-Id: I4a40ccbd3321467a8429fffd1699bd829f342124
Reviewed-by: Andy Shaw <andy.shaw@qt.io>
(cherry picked from commit 472520afb9081856a2556c7df221c084a42a2d42)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 31 insertions, 3 deletions

diff --git a/src/plugins/sqldrivers/mysql/qsql_mysql.cpp b/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
index ea8a15ebfb..289f91a961 100644
--- a/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
+++ b/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
@@ -1235,9 +1235,22 @@ bool QMYSQLDriver::open(const QString& db,
     }
 
     // try utf8 with non BMP first, utf8 (BMP only) if that fails
-    if (mysql_set_character_set(d->mysql, "utf8mb4"))
-        if (mysql_set_character_set(d->mysql, "utf8"))
-            qWarning() << "MySQL: Unable to set the client character set to utf8.";
+    static const char wanted_charsets[][8] = { "utf8mb4", "utf8" };
+#ifdef MARIADB_VERSION_ID
+    MARIADB_CHARSET_INFO *cs = nullptr;
+    for (const char *p : wanted_charsets) {
+        cs = mariadb_get_charset_by_name(p);
+        if (cs) {
+            d->mysql->charset = cs;
+            break;
+        }
+    }
+#else
+    // dummy
+    struct {
+        const char *csname;
+    } *cs = nullptr;
+#endif
 
     if (!sslKey.isNull() || !sslCert.isNull() || !sslCA.isNull() ||
         !sslCAPath.isNull() || !sslCipher.isNull()) {
@@ -1265,6 +1278,21 @@ bool QMYSQLDriver::open(const QString& db,
                                       unixSocket.isNull() ? nullptr : unixSocket.toUtf8().constData(),
                                       optionFlags);
 
+    // now ask the server to match the charset we selected
+    if (!cs || mysql_set_character_set(d->mysql, cs->csname)) {
+        bool ok = false;
+        for (const char *p : wanted_charsets) {
+            if (mysql_set_character_set(d->mysql, p)) {
+                ok = true;
+                break;
+            }
+        }
+        if (!ok)
+            qWarning("MySQL: Unable to set the client character set to utf8 (\"%s\"). Using '%s' instead.",
+                     mysql_error(d->mysql),
+                     mysql_character_set_name(d->mysql));
+    }
+
     if (mysql == d->mysql) {
         if (!db.isEmpty() && mysql_select_db(d->mysql, db.toUtf8().constData())) {
             setLastError(qMakeError(tr("Unable to open database '%1'").arg(db), QSqlError::ConnectionError, d));