On 7/2/2007 1:45 PM, Marko Kreen wrote:
> On 7/2/07, Jan Wieck <JanWieck at yahoo.com> wrote:
>> The stuff I am currently (very slowly) working on is that very problem.
>> Any long running transaction causes that the minxid in the SYNC's is
>> stuck at that very xid during the entire runtime of the LRT. The problem
>> with that is that the log selection in the slon worker uses an index
>> scan who's only index scankey candidates are the minxid of one and the
>> maxxid of another snapshot. That is the range of rows returned by the
>> scan itself. Since the minxid is stuck, it will select larger and larger
>> groups of log tuples only to filter out most of them on a higher level
>> in the query via xxid_le_snapshot().
> 
> How the LRT problem is avoided in PGQ:
> 
> http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/skytools/skytools/sql/pgq/functions/pgq.batch_event_sql.sql?rev=1.2&content-type=text/x-cvsweb-markup
> 
> Basic idea is that there are only few LRT's, so its reasonable
> to pick up bottom half of range by event txid, one-by-one.

Hmmm, that is an interesting idea. And it is (in contrast to what I've 
been playing with) node insensitive, since it doesn't need info only 
available on the event origin, like CLOG. Thanks.


Jan

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