NOTE
How Elasticsearch Indexing Works
Lucene inverted indexes, terms, postings, doc values, segments, and the distinction between search and aggregation data structures.
This is a historical learning note and may contain outdated or incomplete understanding.
Full-text search is powered primarily by Lucene’s inverted-index structures: analyzed terms map to postings describing matching documents and related information needed for scoring/positions depending on field configuration.
Column-oriented doc_values-style storage supports sorting/aggregations for many field types. Stored source/fields serve different retrieval purposes.
Lucene segments are immutable, which enables efficient search snapshots but requires new segments plus merges for updates/deletes. Field mapping choices directly affect which structures are built and therefore index size/performance.