> And while it’s by far the most complex option, one of the nice bits with it would be that the system columns could be packed as well. Currently there’s quite a bit of waste because there are 6 system columns (by default), the first 5 are 4 bytes, but the 6th (ctid) is 6 bytes, meaning 2 bytes of padding if your first column is a SERIAL, and 6 if the first column is a BIGSERIAL (or an other double-aligned column).
FWIW, system columns aren't stored as normal columns in tuples. Some of them are implied (e.g. tableoid doesn't need to be stored in each tuple, ctid is inferred from position), others are not stored in the way normal columns are stored (e.g. xmin, xmax).
FWIW, system columns aren't stored as normal columns in tuples. Some of them are implied (e.g. tableoid doesn't need to be stored in each tuple, ctid is inferred from position), others are not stored in the way normal columns are stored (e.g. xmin, xmax).