{
int i;
+ /*
+ * We set id to -1 if the data file doesn't contain sample
+ * ids. Check for this and avoid walking through the entire
+ * list of ids which may be large.
+ */
+ if (id == -1ULL)
+ return NULL;
+
for (i = 0; i < header->attrs; i++) {
struct perf_header_attr *attr = header->attr[i];
int j;