Bugs item #512826, was opened at 2002-02-04 08:26 You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=376685&aid=512826&group_id=22866
Category: JBossCMP Group: v3.0 Rabbit Hole Status: Open Resolution: None Priority: 5 Submitted By: Georg Schmid (giorgio42) Assigned to: Nobody/Anonymous (nobody) Summary: RH shows quadratic behaviour in inserts Initial Comment: RH 20020105 from CVS, W2K, Oracle 8.1.7. see thread http://main.jboss.org/thread.jsp?forum=46&thread=7700 on JBoss forums. 1) The JDBCStoreCommand.execute generates a disastrous amount of debug output by printing "...NOT updated." for each bean instance it looks at. Getting rid of that would be easy. 2) The root cause of this large amount of debug output is the really interesting issue: Whenever a new bean instance is about to be created the instance cache is "flushed". By this I mean the process where the storage manager walks through the list of all cached instances of the bean class, fetches the list of modified fields, and, if it detects a modification, writes the outstanding modifications to persistent store. The problem with this approach is, that it leads to an O(mn) behaviour, where m is the number of instances in the cache and n is the number of operations, that trigger a flush on the cache. Imagine this scenario: the instance cache is configured to hold 10000 instances. Now a bulk insert of 5000 new instances (as often occurs when importing data from an external table) is started. On the first insert JDBCStoreCommand.execute has to check 0 instances, on the second insert one instance, on the third insert two instances and so on. All in all the execute() method will be called (1 + 2 + 3 + ... + n-1) times where n is the number of inserts, resulting in (n-1)*(n-2)/2 calls to execute. In the case of 5000 new instances this means that there are 4999*4998/2 = 12492501, ie. more than 12 millions calls to execute(). The core problem is the strategy for detecting modified instances: instead of looking at each instance and deciding whether it has to be updated on each instance cache flush, the modified instances should be registered in a "modified instance" list, so that no extra effort is needed to detect "dirty" instances. Instead the set of modified instances would already be known. Commenting out the debug message reduces the time it takes to insert 3464 rows from more than 700 seconds to 225 seconds. ---------------------------------------------------------------------- You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=376685&aid=512826&group_id=22866 _______________________________________________ Jboss-development mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/jboss-development
