Support intervals query with Fast Vector Highlighter

[ZeusFSX]

I have a document, for example:

{
    "text": "Index Down Jones",
    "title": "Index Down Jones"
}

And my mapping for text and title the same:

  "mappings": {
    "properties": {
      "text": {
        "type": "text",
        "analyzer": "my_analyzer",
        "term_vector": "with_positions_offsets",
        "fields": {
          "exact": {
            "type": "text",
            "term_vector": "with_positions_offsets",
            "analyzer": "default"
          },
          "keyword": {
            "type": "keyword",
            "ignore_above": 256
          }
        }
      }

My query:

{
    "query": {
        "bool": {
            "should": [
                {
                    "intervals": {
                        "text": {
                            "all_of": {
                                "intervals": [
                                    {
                                        "match": {
                                            "query": "Down"
                                           }
                                    },
                                    {
                                        "match": {
                                            "analyzer": "default",
                                            "max_gaps": 0,
                                            "query": "Jones",
                                            "use_field": "text.exact"
                                        }
                                    }
                                ],
                                "max_gaps": 0,
                                "ordered": False}
                        }
                    }
                },
                {
                    "intervals": {
                        "title": {
                            "all_of": {
                                "intervals": [
                                    {
                                        "match": {
                                            "query": "Down"
                                         }
                                     },
                                    {
                                        "match": {
                                            "analyzer": "default",
                                            "max_gaps": 0,
                                            "query": "Jones",
                                            "use_field": "title.exact"
                                        }
                                    }
                                ],
                                "max_gaps": 0,
                                "ordered": False
                            }
                        }
                    }
                }
            ]
        }
    },
    "highlight": {
        "number_of_fragments": 0,
        "post_tags": ["</em>"],
        "pre_tags": ["<em>"]},
        "fields": {
            "text": {
                "matched_fields": ["text", "text.exact"],
                "type": "fvh"
            },
            "title": {
                "matched_fields": ["title", "title.exact"],
                "type": "fvh"
            }
        }
}

Can you add support to fast vector highlighter when use intervals query?
By the way, when I use unified highlighter elasticsearch highlights fields separately:

"highlight": {
    "text.exact": ["Index Down <em>Jones</em>"],
    "title.exact": ["Index Down <em>Jones</em>"],
    "text": ["Index <em>Down</em> Jones"],
    "title": ["Index <em>Down</em> Jones"]
}

[elasticmachine]

Pinging @elastic/es-search (Team:Search)

[jimczi]

The Fast vector highlighter is in maintenance mode so all developments are now made on the unified highlighter.
There are no more activities in Lucene for this highlighter as well so the chance that intervals are handled by this old highlighter are very small. For this reason I hope you don't mind if I close this issue, if something is missing or not working with the unified highlighter please open a new one.

[ZeusFSX]

@jimczi Do you have any advice for highlight, how to merge two fields into one: text and text.exact using unified highlighter?

[jimczi]

That's tracked in #5172 @ZeusFSX . The fact that the issue is still opened is a good indicator that we want to implement it, however this is a high hanging fruit and we never had the time, due to other prioritization, to address it properly. I am afraid that this will not change in the near future but we'll get to it eventually. The linked issue also provides some workaround in the meantime.

[ZeusFSX]

@jimczi Thanks)))