Re: [luciddb-users] LucidDB Gets Stuck Processing Many Concurrent Queries

[Nicholas G. <ngo...@ba...>]

On May 31, 2011, at 2:18 PM, victor.savkin wrote:

> I have a heavy query. I'm trying to run this query in parallel using X
> threads.
How are you trying to do parallel?  Are they all separate connections, queries that you are running separately or are you using a UNIONed dataset with degreeOfParallelism?

> But each time I'm running it in 8 threads I got 7 responses but 1 thread
> always gets stuck. I don't get any answer from luciddb. If I run all 8
> queries with a small random delay, so they won't be started at the same time
> it works fine. Could you help me to understand what is causing the issue? 
Can you determine if all 8 queries are being executed (check the Trace.log for the statement logging).

I know of no artificial limit to 8 threads.  If one is being run, but is stuck you should also see it in http://pub.eigenbase.org/wiki/LucidDbSystemViews#DBA_SQL_STATEMENTS

Can you confirm that you see 8 records for your queries in there, and that 7 of the 8 return successfully (disappear) but that one remains?