backend_tx_run_single_int
int backend_tx_run_single_int(backend_tx_t *tx, backend_query_t *q,
rc = backend_tx_run_single_int(tx, q, &id);
rc = backend_tx_run_single_int(tx_ro, q, &id);
rc = backend_tx_run_single_int(tx_wr, q, &id);
result = backend_tx_run_single_int(tx, q, &oldsnapid);
r = backend_tx_run_single_int(tx, q, &gen);
r = backend_tx_run_single_int(tx, q, &snapid);