question about mergeFactor

[Marc Des Garets <ma...@192.com>]

Hello,

 

On the solr wiki, here:
http://wiki.apache.org/solr/SolrPerformanceFactors

 

It is written:

mergeFactor Tradeoffs

 

High value merge factor (e.g., 25):

Pro: Generally improves indexing speed

Con: Less frequent merges, resulting in a collection with more index
files which may slow searching

Low value merge factor (e.g., 2):

 

Pro: Smaller number of index files, which speeds up searching.

Con: More segment merges slow down indexing.

 

If I have a mergeFactor of 50 when I build the index and then I optimize
the index, I end up with 1 index file so I have a small number of index
files and having used mergeFactor of 50 won't slow searching? Or my
supposition is wrong and the mergeFactor used when building the index
has an impact on speed searching anyway?

 

 

Thanks.
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RE: question about mergeFactor

[Marc Des Garets <ma...@192.com>]

Perfect. Thank you for your help.

-----Original Message-----
From: Shalin Shekhar Mangar [mailto:shalinmangar@gmail.com] 
Sent: 08 March 2010 12:57
To: solr-user@lucene.apache.org
Subject: Re: question about mergeFactor

On Mon, Mar 8, 2010 at 5:31 PM, Marc Des Garets
<ma...@192.com>wrote:

>
> If I have a mergeFactor of 50 when I build the index and then I
optimize
> the index, I end up with 1 index file so I have a small number of
index
> files and having used mergeFactor of 50 won't slow searching? Or my
> supposition is wrong and the mergeFactor used when building the index
> has an impact on speed searching anyway?
>
>
If you optimize then mergeFactor does not matter and your searching
speed
will not be slowed down. On the other hand, the optimize may take the
bulk
of the indexing time, so you won't get any benefit from using a
mergeFactor
of 50.

-- 
Regards,
Shalin Shekhar Mangar.
----------------------------------------------------------
This transmission is strictly confidential, possibly legally privileged, and intended solely for the 
addressee.  Any views or opinions expressed within it are those of the author and do not necessarily 
represent those of 192.com, i-CD Publishing (UK) Ltd or any of it's subsidiary companies.  If you 
are not the intended recipient then you must not disclose, copy or take any action in reliance of this 
transmission. If you have received this transmission in error, please notify the sender as soon as 
possible.  No employee or agent is authorised to conclude any binding agreement on behalf of 
i-CD Publishing (UK) Ltd with another party by email without express written confirmation by an 
authorised employee of the Company. http://www.192.com (Tel: 08000 192 192).  i-CD Publishing (UK) Ltd 
is incorporated in England and Wales, company number 3148549, VAT No. GB 673128728.

Re: question about mergeFactor

[Shalin Shekhar Mangar <sh...@gmail.com>]

On Mon, Mar 8, 2010 at 5:31 PM, Marc Des Garets <ma...@192.com>wrote:

>
> If I have a mergeFactor of 50 when I build the index and then I optimize
> the index, I end up with 1 index file so I have a small number of index
> files and having used mergeFactor of 50 won't slow searching? Or my
> supposition is wrong and the mergeFactor used when building the index
> has an impact on speed searching anyway?
>
>
If you optimize then mergeFactor does not matter and your searching speed
will not be slowed down. On the other hand, the optimize may take the bulk
of the indexing time, so you won't get any benefit from using a mergeFactor
of 50.

-- 
Regards,
Shalin Shekhar Mangar.