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

Hi Alexander,

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?

-- 
Ildar Musin
i.musin@postgrespro.ru