>The hierarchy breakdown in the article is misleading. Lucene indexes fields, not documents. Understanding this is key. More fields == more files. Segments are per field not per ES index. A lucene index is not the same as an Elasticsearch index.
Unless I'm mistaken, segments are not per field.
A lucene index might be broken into segments depending on your merge policy, but the segment file structure allows it to be an effectively separate lucene index that you can search on and contains data for all the index fields.
And I too find the fact that the term "index" is reused by ES to mean a collection of lucene indexes. Once someone wants to dive deeper it only creates ambiguity.
Unless I'm mistaken, segments are not per field. A lucene index might be broken into segments depending on your merge policy, but the segment file structure allows it to be an effectively separate lucene index that you can search on and contains data for all the index fields.
And I too find the fact that the term "index" is reused by ES to mean a collection of lucene indexes. Once someone wants to dive deeper it only creates ambiguity.