code: func (mp *LogMergePolicy) SetMergeFactor(mergeFactor int) {
  	assert2(mergeFactor >= 2, "mergeFactor cannot be less than 2")
  	mp.mergeFactor = mergeFactor
  }
docs: /*
  Determines how often segment indices are merged by AdDocument(). With
  smaller values, less RAM is used while indexing, and searches are
  faster, but indexing speed is slower. With larger values, more RAM is
  used during indexing, and while searches is slower, indexing is
  faster. Thus larger values (> 10) are best for batch index creation,
  and smaller values (< 10) for indces that are interactively
  maintained.
  */