write
Write all fields, terms and postings. This the "pull" API, allowing you to iterate more than once over the postings, somewhat analogous to using a DOM API to traverse an XML tree.
Notes:
You must compute index statistics, including each Term's docFreq and totalTermFreq, as well as the summary sumTotalTermFreq, sumTotalDocFreq and docCount.
You must skip terms that have no docs and fields that have no terms, even though the provided Fields API will expose them; this typically requires lazily writing the field or term until you've actually seen the first term or document.
The provided Fields instance is limited: you cannot call any methods that return statistics/counts; you cannot pass a non-null live docs when pulling docs/positions enums.