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From Shawn Heisey <>
Subject Re: Default merge policy
Date Fri, 12 Oct 2018 16:57:14 GMT
On 10/12/2018 8:32 AM, root23 wrote:
> We are on solr 6.  and as per the documentation i think solr 6 uses
> TieredMergePolicyFactory.
> However we have not specified it in the following way
> <mergePolicyFactory class="org.apache.solr.index.TieredMergePolicyFactory">
>    <int name="maxMergeAtOnce">10</int>
>    <int name="segmentsPerTier">10</int>
> </mergePolicyFactory>
> We still use <mergeFactor>25</mergeFactor>. which i understand is not used
> by TieredMergePolicyFactory.

Supplementing what Erick said.  Erick's info is completely valid.

For the version you are on, specifying a mergeFactor of 25 with no other 
merge-policy related config effectively results in this config:

<mergePolicyFactory class="org.apache.solr.index.TieredMergePolicyFactory">
   <int name="maxMergeAtOnce">25</int>
   <int name="segmentsPerTier">25</int>
   <int name="maxMergeAtOnceExplicit">30</int>

I would recommend replacing mergeFactor with an explicit merge policy 
config.  Since you are going with numbers higher than default, you 
should set maxMergeAtOnceExplicit to three times the value of the other 
two settings.  In this case, that would be 75.


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