Re: [HACKERS] Challenges preventing us moving to 64 bit transactionid (XID)?

On 22.06.2017 18:36, Alexander Korotkov wrote:

On Wed, Jun 7, 2017 at 11:33 AM, Alexander Korotkov
<a.korotkov@postgrespro.ru <mailto:a.korotkov@postgrespro.ru>> wrote:

0002-heap-page-special-1.patch
Putting xid and multixact bases into PageHeaderData would take extra 16
bytes on index pages too.  That would be waste of space for indexes.
This is why I decided to put bases into special area of heap pages.
This patch adds special area for heap pages contaning prune xid and
magic number.  Magic number is different for regular heap page and
sequence page.

We've discussed it earlier but it worth mentioning here too. You have pd_prune_xid of type TransactionId which is treated elsewhere as ShortTransactionId (see HeapPageGetPruneXid() and HeapPageSetPruneXid()) and hence introduces redundant 4 bytes. Could you please fix it?