Workaround for bug #708

An almost empty `global_variables` is added on stats schema. This will allow to run queries against it, even if empty.

lib/ProxySQL_Admin.cpp

@@ -2539,6 +2539,7 @@ bool ProxySQL_Admin::init() {
 	insert_into_tables_defs(tables_defs_stats,"stats_mysql_query_digest", STATS_SQLITE_TABLE_MYSQL_QUERY_DIGEST);
 	insert_into_tables_defs(tables_defs_stats,"stats_mysql_query_digest_reset", STATS_SQLITE_TABLE_MYSQL_QUERY_DIGEST_RESET);
 	insert_into_tables_defs(tables_defs_stats,"stats_mysql_global", STATS_SQLITE_TABLE_MYSQL_GLOBAL);
+	insert_into_tables_defs(tables_defs_stats,"global_variables", ADMIN_SQLITE_TABLE_GLOBAL_VARIABLES); // workaround for issue #708
 
 	// upgrade mysql_servers if needed (upgrade from previous version)
 	disk_upgrade_mysql_servers();
@@ -2578,6 +2579,10 @@ bool ProxySQL_Admin::init() {
 	__insert_or_replace_maintable_select_disktable();
 
 	flush_admin_variables___database_to_runtime(admindb,true);
+
+	// workaround for issue #708
+	statsdb->execute("INSERT OR IGNORE INTO global_variables VALUES('mysql-max_allowed_packet',4194304)");
+
 #ifdef DEBUG
 	if (GloVars.global.gdbg==false && GloVars.__cmd_proxysql_gdbg) {
 		proxy_debug(PROXY_DEBUG_ADMIN, 4, "Enabling GloVars.global.gdbg because GloVars.__cmd_proxysql_gdbg==%d\n", GloVars.__cmd_proxysql_gdbg);