code: func NewIndexWriterConfig(matchVersion util.Version, analyzer analysis.Analyzer) *IndexWriterConfig {
  	return &IndexWriterConfig{
  		LiveIndexWriterConfigImpl: newLiveIndexWriterConfig(analyzer, matchVersion),
  		writer: util.NewSetOnce(),
  	}
  }
docs: /*
  Creates a new config that with defaults that match the specified
  Version as well as the default Analyzer. If matchVersion is >= 3.2,
  TieredMergePolicy is used for merging; else LogByteSizeMergePolicy.
  Note that TieredMergePolicy is free to select non-contiguous merges,
  which means docIDs may not remain monotonic over time. If this is a
  problem, you should switch to LogByteSizeMergePolicy or
  LogDocMergePolicy.
  */