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From Dan OConnor <>
Subject Re: is there a way to control when merges happen?
Date Fri, 15 May 2009 20:56:09 GMT
Thank for the reply. 

A follow up question. 
How can I tell the big merges from the small ones?  


----- Original Message -----
From: Michael McCandless <>
To: <>
Sent: Fri May 15 16:50:27 2009
Subject: Re: is there a way to control when merges happen?

I think you could subclass ConcurrentMergeScheduler, overriding
merge() to only call super.merge() if the time is right?  (And just
return right away if it's not the right time).

Though you might want to allow small merges to run in real-time, and
big merges to wait until after hours.


On Fri, May 15, 2009 at 4:41 PM, Dan OConnor <> wrote:
> All:
> I would like to be able to control when an index merge happens (by wall clock time) so
that merges do not occur in the middle of the business day.
> I have a lucene system based on v2.3.2 and we add a couple hundred thousand documents
per day - and we allow searching while documents are being added - we reopen an IndexReader
periodically to expose newly arrived contents.
> There are times when merging causes significant performance impacts on search results
- I've seen cases where merging will cause 200% load on a system (dual quad core x86_64 running
Centos) with a raid-5 disk subsystem of 15k drives.
> I've seen some info on the MergeScheduler and ConcurrentMergeScheduler but not necessarily
enough to attempt a coding effort.
> Looking through the code for, is it as straightforward
as over-riding the mergeScheduler.merge() method with a method that checks to see if a merge
is allowed (by wall clock time)?  If a merge is not allowed at that time, can I just return();?
Or do I have to sleep the thread until the merge is allowed?
> Thanks,
> Dan
> Dan O'Connor
> SVP, Engineering
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