
A statement like select if(@@hostname='box02','prod_mariadb02','n'); does not modify @@hostname. Hence the type mask should be QUERY_TYPE_READ|QUERY_TYPE_SYSVAR_READ and NOT QUERY_TYPE_READ|QUERY_TYPE_GSYSVAR_WRITE.
A statement like select if(@@hostname='box02','prod_mariadb02','n'); does not modify @@hostname. Hence the type mask should be QUERY_TYPE_READ|QUERY_TYPE_SYSVAR_READ and NOT QUERY_TYPE_READ|QUERY_TYPE_GSYSVAR_WRITE.