When a document is indexed the ES keep it in 2 ways:
1)_all : used for searching
2)_source : used for reindexing
When we index a document in Lucene, the values for each field are added to the inverted index for the associated field. Optionally, the original values may also be stored unchanged so that they can be retrieved later.
Here _all and _source is done by LUCENE . So, the inverted index is used for _all . Original values are stored in _source.
Correct me if my understanding is wrong?