Commit
88e66d193fbaf756b3cc9bf94cad116aacbb355b is to blame.
Masahiko Sawada
Discussion: http://postgr.es/m/CAD21AoAXeb7O4hgg+efs8JT_SxpR4doAH5c5s-Z5WoRLstBZJA@mail.gmail.com
* The tree can easily be walked from child to parent, but not in the
* opposite direction.
*
+ * This code is based on xact.c, but the robustness requirements
* are completely different from pg_xact, because we only need to remember
* pg_subtrans information for currently-open transactions. Thus, there is
* no need to preserve data over a crash and restart.