[Mulgara-dev] Mulgara Backup File -- Strings listed twice in the string pool?

Ben Hysell BenH at viewpointusa.com
Tue Mar 18 17:42:22 UTC 2008


Everyone,

I have a new interesting issue I've just started to run into over the
past couple of days.  Background...we backup our production Mulgara
server every two hours, unzip the backup file, and read in the whole
string pool.  We then walk through the Triples section, ensuring each
node number listed in the Triples section is in the string pool.  We
then go on to restore the latest backup to an offline server to have
ready in case our production Mulgara goes down.

We have had some difficulties with blank nodes getting into our
production database in the past where we were not allowed to delete
triples and causing all sorts of headaches.  Hence we are very vigilant
now with our system and go through all of this effort with every backup
we produce to catch the issue before it becomes a larger problem.

On to our current issue, during the process of reading in the string
pool entries I'm getting strings being listed twice in the backup file,
i.e.

If early in the backup file I have
999  a less interesting string
1000 My fancy string
1001 some other string

Later on in the file I'll also have
49998 A new string
1000 My fancy string
49999 Another new string

The listing of 'My fancy string' with the same node number '1000'
appears twice in the string pool.  Any thoughts on how this could be
happening?

To throw another twist to the situation, this happened yesterday and the
resulting check through the Triples revealed I had gained over 1000
blank nodes into the system.  Yesterday we restored back to a database
we knew had no blank nodes in it, moved it to production, and ran for
the last 20 hours without incident.  This morning, no new blank nodes,
but at 12 noon our backup application reported multiple string pool
entries, but no blank nodes.  I'm not sure if I caught the system before
it was about to experience a blank node explosion or not...

Any thoughts on anything we could be checking for doing differently?
Thanks

-ben



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