Highlighting

Highlighting #

Ask for matched fragments of your text fields back alongside each hit, with the matched terms wrapped in tags — ready to render as a search result list.

POST /my-collection/_search

How it works #

Highlighting is an engine-native enrich step that runs on the returned page only — after ranking and truncation, exactly like script fields. It has two phases (lib/engine/src/search/highlight/):

1. Term extraction. The engine walks the query tree and collects (field, term) pairs worth highlighting: term, terms, fuzzy, span_term, intervals, match, multi_match, match_phrase, and bool clauses. Text queries (match, multi_match, phrase) are re-tokenized through the field’s search analyzer (or the query’s explicit analyzer override), so the highlighted terms mirror what the query scored. must_not clauses never contribute — documents excluded by them get no tags from them. match_all, range, geo and vector queries carry nothing to highlight.