private boolean shouldAssignFavoredNodes(RegionInfo region) {
    return this.shouldAssignRegionsWithFavoredNodes
      && FavoredNodesManager.isFavoredNodeApplicable(region);
  }
When called here, the merge has happened. The merged regions have been unassigned and the above
markRegionClosed has been called on each so they have been disassociated from a hosting Server.
The merged region will be open after this call. The merged regions are removed from hbase:meta
below. Later they are deleted from the filesystem by the catalog janitor running against
hbase:meta. It notices when the merged region no longer holds references to the old regions
(References are deleted after a compaction rewrites what the Reference points at but not until
the archiver chore runs, are the References removed).
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignmentManager.java