I don't quite understand this part of the comment of the xl_heap_header
structure:
* NOTE: t_hoff could be recomputed, but we may as well store it because
* it will come for free due to alignment considerations.
What are the alignment considerations? The WAL code does not appear to assume
any alignment, and therefore it uses memcpy() to copy the structure into a
local variable before accessing its fields. For example, heap_xlog_insert().
--
Antonin Houska
Web: https://www.cybertec-postgresql.com