Question about WAL and XID

Hi,

am I right that an XID is global across the whole DB cluster
under the same $PGDATA? I am asking because in the WAL
record, the first thing sent is an XLogRecord which contains
   TransactionId xl_xid;

and as the comment in access/xlog.h says:

/** The overall layout of an XLOG record is:*              Fixed-size header (XLogRecord struct)*
rmgr-specificdata*              BkpBlock*              backup block data*              BkpBlock*              backup
blockdata*              ...
 

And the BkpBlock structure contains the RelFileNode info,
the triplet for tablespace/database/relation.

Or is it completely backwards?

I am asking this because I need to check   TransactionIdDidCommit(XLogRecord->xl_xid)
from the walreciver. Can I expect it to work on any
xl_xid that walreceiver encounters?

Best regards,
Zoltán Böszörményi

-- 
Bible has answers for everything. Proof:
"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more
than these cometh of evil." (Matthew 5:37) - basics of digital technology.
"May your kingdom come" - superficial description of plate tectonics

----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/