Re: Next step towards 64bit XIDs: Switch to FullTransactionId for PGPROC->xid and XLogRecord->xl_xid

Hi!

As were discussed in [0] our overall goal is to make Postgres 64 bit XIDs.  It's obvious, that such a big patch set

couldn't possible to commit "at once".  SLUR patch set [1] was committed a short while ago as a first significant 

step in this direction.

This thread is a next step in this enterprise.  My objective here is to commit some changes, which were mandatory,

as far as I understand, for any type of 64 XIDs implementation. And I'm sure there will be points for discussion here.

My original intention was to make PGPROC->xmin, PGPROC->xid and PROC_HDR->xids 64bit.  But in reality, 

it turned out to be much more difficult than I expected.  On the one hand, the patch became too big and on the other

hand, it's heavily relayed on epoch and XID "adjustment" to FXID.  Therefore, for now, I decided to limit myself to 

more atomic and independent changes. However, as I said above, these changes are required for any implementation

of 64bit XIDs.

So, PFA patches to make switch PGPROC->xid 

and XLogRecord->xl_xid to FullTransactionId.