On 7/2/2019 10:53 PM, Rahul Goswami wrote:
Hi Shawn,
Thank you for the detailed suggestions. Although, I would like to
understand the maxMergeCount and maxThreadCount params better. The
documentation
<https://lucene.apache.org/solr/guide/7_3/indexconfig-in-solrconfig.html#mergescheduler>
mentions
that
maxMergeCount : The maximum number of simultaneous merges that are allowed.
maxThreadCount : The maximum number of simultaneous merge threads that
should be running at once
Since one thread can only do 1 merge at any given point of time, how does
maxMergeCount being greater than maxThreadCount help anyway? I am having
difficulty wrapping my head around this, and would appreciate if you could
help clear it for me.
The maxMergeCount setting controls the number of merges that can be
*scheduled* at the same time. As soon as that number of merges is
reached, the indexing thread(s) will be paused until the number of
merges in the schedule drops below this number. This ensures that no
more merges will be scheduled.
By setting maxMergeCount higher than the number of merges that are
expected in the schedule, you can ensure that indexing will never be
paused. It would require very atypical merge policy settings for the
number of scheduled merges to ever reach six. On my own indexing, I
reached three scheduled merges quite frequently. The default setting
for maxMergeCount is three.
The maxThreadCount setting controls how many of the scheduled merges
will be simultaneously executed. With index data on standard spinning
disks, you do not want to increase this number beyond 1, or you will
have a performance problem due to thrashing disk heads. If your data is
on SSD, you can make it larger than 1.
Thanks,
Shawn
