Hi Pavel, > Please feel free to discuss readme and your opinions on the current patch and > proposed changes [1].
Just a quick question about this design choice: > On-disk tuple format remains unchanged. 32-bit t_xmin and t_xmax store the > lower parts of 64-bit XMIN and XMAX values. Each heap page has additional > 64-bit pd_xid_base and pd_multi_base which are common for all tuples on a > page. > They are placed into a pd_special area - 16 bytes in the end of a heap page. > Actual XMIN/XMAX for a tuple are calculated upon reading a tuple from a page > as follows: > > XMIN = t_xmin + pd_xid_base. > XMAX = t_xmax + pd_xid_base/pd_multi_base. Did you consider using 4 bytes for pd_xid_base and another 4 bytes for (pd_xid_base/pd_multi_base)? This would allow calculating XMIN/XMAX as: XMIN = (t_min_extra_bits << 32) | t_xmin XMAX = (t_max_extra_bits << 32) | t_xmax ... and save 8 extra bytes in the pd_special area. Or maybe I'm missing some context here? -- Best regards, Aleksander Alekseev
