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-specific data
* BkpBlock
* backup block data
* BkpBlock
* backup block data
* ...

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