elastic, kibana 6.5.0
I have done some testing, in dev environment, and I have noticed something.
In kibana: management -> index management --> force merge.
It says, that default value is 1, but if I run this, then it actually does nothing, and number of segments per shard is still 9 (as it was before).
It seems to me that actually default value is:
Defaults to simply checking if a merge needs to execute, and if so, executes it.
So it will just check, if it needs to to something.
And for example, if I insert value lower than current_segment_per_shard and higher than 1, then it will actually still use 1, so for example:
current_segment_per_shard = 9
I do force merge through kibana on an specific index, and insert value 7
then after the force merge action, I have 1 segment per shard.
So the setting that I inserted, 7, does not make no difference.