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More clarifications on the unified highlighter being the new default (#25668) 

* More clarifications on the unified highlighter being the new default
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Jim Ferenczi 2017-07-13 15:38:58 +02:00 committed by GitHub
parent 13da3eb53e
commit fe383b7c27
1 changed files with 6 additions and 8 deletions
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docs/reference/search/request/highlighting.asciidoc
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@ -60,7 +60,7 @@ index and re-runs the original query criteria through Lucene's query execution
planner to get access to low-level match information for the current document.
This is repeated for every field and every document that needs to be highlighted.
If you want to highlight a lot of fields in a lot of documents with complex
queries, we recommend using one of the other highlighters.
queries, we recommend using the `unified` highlighter on `postings` or `term_vector` fields.
[[fast-vector-highlighter]]
==== Fast vector highlighter
@ -68,8 +68,7 @@ The `fvh` highlighter uses the Lucene Fast Vector highlighter.
This highlighter can be used on fields with `term_vector` set to
`with_positions_offsets` in the mapping. The fast vector highlighter:
* Is faster especially for large fields (> `1MB`)
* Can be customized with a <<boundary-scanners,`boundary_scanner`>>.
* Can be customized with a <<boundary-scanners,`boundary_scanner`>>.
* Requires setting `term_vector` to `with_positions_offsets` which
increases the size of the index
* Can combine matches from multiple fields into one result. See
@ -95,12 +94,11 @@ disk space than using `term_vectors`.
* Term vectors. If `term_vector` information is provided by setting
`term_vector` to `with_positions_offsets` in the mapping, the `unified`
highlighter automatically uses the `term_vector` to highlight the field.
Term vector highlighting is faster for highlighting multi-term queries like
`prefix` or `wildcard` because it can access the dictionary of terms for
each document, but it can be slower than using the postings list. The `fvh`
highlighter always uses term vectors.
It's fast especially for large fields (> `1MB`) and for highlighting multi-term queries like
`prefix` or `wildcard` because it can access the dictionary of terms for each document.
The `fvh` highlighter always uses term vectors.
* Plain highlighting. This mode is used when there is no other alternative.
* Plain highlighting. This mode is used by the `unified` when there is no other alternative.
It creates a tiny in-memory index and re-runs the original query criteria through
Lucene's query execution planner to get access to low-level match information on
the current document. This is repeated for every field and every document that