backend_run
int backend_run(backend_type_t, backend_query_t *,
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_pg_callback, &ci);
res = backend_run(BACKEND_TYPE_NONPERSIST, q,
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_snapshot_callback, &ci);
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_pg_callback, &ci);
result = backend_run(BACKEND_TYPE_NORMAL, q, fill_snapshot_cb, sp);
result = backend_run(BACKEND_TYPE_NORMAL, q, check_snapshot_fill_cb,
result = backend_run(BACKEND_TYPE_NORMAL, q, check_snapshot_check_cb,
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_child_callback, &ci);
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_child_callback, &ci);
res = backend_run(BACKEND_TYPE_NORMAL, q, fill_pg_callback, &ci);
res = backend_run(BACKEND_TYPE_NONPERSIST, q,