We have had no luck with performance of parallel transactions as well.
Refer to the original thread named: "concurrent read access" (Oct
2008).
Included for convenience - here's the text of that problem description:
>>>>>>>>> BEGIN excerpt from [Sedna-discussion] concurrent read access
>>>>>>>>>>>>>>>
We have a setup where we have multiple threads using the Java API driver
- Each thread opens one connection to the DB
- In that connection it executes one read query repeatedly (say 200
times)
The document in the DB is the basic 'auctions' document.
The query is as follows:
==========
(:
Return the initial increases of all open auctions.
:)
for $b in document("auction")/site/open_auctions/open_auction
return <increase>{ $b/bidder[position()=1]/increase/text() }</increase>
==========
We find that with just 1 thread running - average times for execution of
each query are in the 16ms range
If we increase the thread count to 2/3 - the times for each query seem
to corresondingly double/triple.
Running 9 threads puts the time for each query in the 200ms range.
It appears that we are not truly getting concurrent access - and all the
querys are being executed sequentially.
We have tried the following:
- create different collections for each thread to query in - ie same
document replicated in N collections - one for each thread. That makes
no difference.
>>>>>>>>> END excerpt from [Sedna-discussion] concurrent read access
>>>>>>>>>>>>>>>
-----Original Message-----
From: Mark Waschkowski [mailto:[email protected]]
Sent: Monday, January 26, 2009 4:44 PM
To: [email protected]
Subject: Re: [Sedna-discussion] performance issues
Hi Ivan,
What do you mean by:
"Performance degrades in some situations when you run parallel
transactions which extensively use IO. "
Is it typical to see 25% performance with 2 threads? I wouldn't expect
2 threads to degrade in performance in typical usages.
Ming - what kinds of queries are these thread doing?
Thanks,
Mark
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