An index merge policy controls how the Dgraph manages its index
files. A balanced index merge policy is used by default, and, in the majority
of deployments, you do not need to change it.
About an index merge policy
An index merge policy determines how frequently the Dgraph merges incremental update generations in its index files.
Manually forcing a merge
Manually forcing a merge is considered a one-time option, because after the merge operation is performed (via a temporary aggressive change to the merge policy), the merge policy reverts to its previous setting.
Linux ulimit settings for merges
For purposes of generation merging, it is recommended that you set the Linux option ulimit-v and -m parameters to unlimited.