Re: Question about WAL and XID

Hi,

Heikki Linnakangas írta:
> Boszormenyi Zoltan wrote:
>   
>> am I right that an XID is global across the whole DB cluster
>> under the same $PGDATA?
>>     
>
> Yes.
>
>   
>> 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?
>>     
>
> Walreceiver is only responsible for receiving the WAL from the master
> server, and write to disk. It doesn't apply the log, it doesn't look
> into the contents at all. So TransactionIdDidCommit(XLogRecord->xl_xid)
> always returns false on WAL it has received, because it hasn't been
> applied yet.
>   

I guessed so, I intended to collect the xl_xid values in a cache array
and check periodically.

> What are you trying to do?
>   

Synchronous replication. :-)

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/