The basic implementation of WiredTiger random cursors doesn't do a very good job if the tree is unbalanced.
There is an enhanced next_random implementation that gives a pseudo random set of keys distributed somewhat evenly across the file. In order to use the new functionality it's necessary to tell WiredTiger approximately how many samples are going to be taken.
- is related to
WT-2262 Random sampling is skewed by tree shape
- related to
SERVER-55821 remove next_random_sample_size=1000 configuration in the oplog sampling code