WARNING: Version 5.x has passed its EOL date.
This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.
Highlighting Usage
editHighlighting Usage
editAllows to highlight search results on one or more fields.
The implementation uses either the lucene highlighter, fast-vector-highlighter or postings-highlighter.
See the Elasticsearch documentation on highlighting for more detail.
Fluent DSL example
edits => s
.Query(q => q
.Match(m => m
.Field(f => f.Name.Suffix("standard"))
.Query("Upton Sons Shield Rice Rowe Roberts")
)
)
.Highlight(h => h
.PreTags("<tag1>")
.PostTags("</tag1>")
.Encoder("html")
.Fields(
fs => fs
.Field(p => p.Name.Suffix("standard"))
.Type("plain")
.ForceSource()
.FragmentSize(150)
.Fragmenter(HighlighterFragmenter.Span)
.NumberOfFragments(3)
.NoMatchSize(150),
fs => fs
.Field(p => p.LeadDeveloper.FirstName)
.Type(HighlighterType.Fvh)
.PreTags("<name>")
.PostTags("</name>")
.BoundaryMaxScan(50)
.PhraseLimit(10)
.HighlightQuery(q => q
.Match(m => m
.Field(p => p.LeadDeveloper.FirstName)
.Query("Kurt Edgardo Naomi Dariana Justice Felton")
)
),
fs => fs
.Field(p => p.State.Suffix("offsets"))
.Type(HighlighterType.Postings)
.PreTags("<state>")
.PostTags("</state>")
.HighlightQuery(q => q
.Terms(t => t
.Field(f => f.State.Suffix("offsets"))
.Terms(
StateOfBeing.Stable.ToString().ToLowerInvariant(),
StateOfBeing.BellyUp.ToString().ToLowerInvariant()
)
)
)
)
)
Object Initializer syntax example
editnew SearchRequest<Project>
{
Query = new MatchQuery
{
Query = "Upton Sons Shield Rice Rowe Roberts",
Field = "name.standard"
},
Highlight = new Highlight
{
PreTags = new[] { "<tag1>" },
PostTags = new[] { "</tag1>" },
Encoder = "html",
Fields = new Dictionary<Field, IHighlightField>
{
{
"name.standard", new HighlightField
{
Type = HighlighterType.Plain,
ForceSource = true,
FragmentSize = 150,
Fragmenter = HighlighterFragmenter.Span,
NumberOfFragments = 3,
NoMatchSize = 150
}
},
{
"leadDeveloper.firstName", new HighlightField
{
Type = "fvh",
PhraseLimit = 10,
BoundaryMaxScan = 50,
PreTags = new[] { "<name>" },
PostTags = new[] { "</name>" },
HighlightQuery = new MatchQuery
{
Field = "leadDeveloper.firstName",
Query = "Kurt Edgardo Naomi Dariana Justice Felton"
}
}
},
{
"state.offsets", new HighlightField
{
Type = HighlighterType.Postings,
PreTags = new[] { "<state>" },
PostTags = new[] { "</state>" },
HighlightQuery = new TermsQuery
{
Field = "state.offsets",
Terms = new[] { "stable", "bellyup" }
}
}
}
}
}
}
Example json output.
{
"query": {
"match": {
"name.standard": {
"query": "Upton Sons Shield Rice Rowe Roberts"
}
}
},
"highlight": {
"pre_tags": [
"<tag1>"
],
"post_tags": [
"</tag1>"
],
"encoder": "html",
"fields": {
"name.standard": {
"type": "plain",
"force_source": true,
"fragment_size": 150,
"fragmenter": "span",
"number_of_fragments": 3,
"no_match_size": 150
},
"leadDeveloper.firstName": {
"type": "fvh",
"phrase_limit": 10,
"boundary_max_scan": 50,
"pre_tags": [
"<name>"
],
"post_tags": [
"</name>"
],
"highlight_query": {
"match": {
"leadDeveloper.firstName": {
"query": "Kurt Edgardo Naomi Dariana Justice Felton"
}
}
}
},
"state.offsets": {
"type": "postings",
"pre_tags": [
"<state>"
],
"post_tags": [
"</state>"
],
"highlight_query": {
"terms": {
"state.offsets": [
"stable",
"bellyup"
]
}
}
}
}
}
}
Handling Responses
editresponse.ShouldBeValid();
foreach (var highlightsInEachHit in response.Hits.Select(d => d.Highlights))
{
foreach (var highlightField in highlightsInEachHit)
{
if (highlightField.Key == "name.standard")
{
foreach (var highlight in highlightField.Value.Highlights)
{
highlight.Should().Contain("<tag1>");
highlight.Should().Contain("</tag1>");
}
}
else if (highlightField.Key == "leadDeveloper.firstName")
{
foreach (var highlight in highlightField.Value.Highlights)
{
highlight.Should().Contain("<name>");
highlight.Should().Contain("</name>");
}
}
else if (highlightField.Key == "state.offsets")
{
foreach (var highlight in highlightField.Value.Highlights)
{
highlight.Should().Contain("<state>");
highlight.Should().Contain("</state>");
}
}
else
Assert.True(false, $"highlights contains unexpected key {highlightField.Key}");
}
}
Unified highlighter
editThe unified highlighter can extract offsets from either postings, term vectors, or via re-analyzing text. Under the hood it uses Lucene UnifiedHighlighter which picks its strategy depending on the field and the query to highlight.
Unified highlighter is available only in Elasticsearch 5.3.0+
This functionality is experimental and may be changed or removed completely in a future release. Elastic will take a best effort approach to fix any issues, but experimental features are not subject to the support SLA of official GA features.
Fluent DSL example
edits => s
.Query(q => q
.Match(m => m
.Field(f => f.Name.Suffix("standard"))
.Query("Upton Sons Shield Rice Rowe Roberts")
)
)
.Highlight(h => h
.Fields(
fs => fs
.Field(p => p.LeadDeveloper.LastName)
.Type(HighlighterType.Unified)
.PreTags("<name>")
.PostTags("</name>")
.HighlightQuery(q => q
.Match(m => m
.Field(p => p.LeadDeveloper.LastName)
.Query(LastNameSearch)
)
)
)
)
Object Initializer syntax example
editnew SearchRequest<Project>
{
Query = new MatchQuery
{
Query = "Upton Sons Shield Rice Rowe Roberts",
Field = "name.standard"
},
Highlight = new Highlight
{
Fields = new Dictionary<Field, IHighlightField>
{
{
"leadDeveloper.lastName", new HighlightField
{
Type = HighlighterType.Unified,
PreTags = new[] { "<name>" },
PostTags = new[] { "</name>" },
HighlightQuery = new MatchQuery
{
Field = "leadDeveloper.lastName",
Query = LastNameSearch
}
}
}
}
}
}
Example json output.
{
"query": {
"match": {
"name.standard": {
"query": "Upton Sons Shield Rice Rowe Roberts"
}
}
},
"highlight": {
"fields": {
"leadDeveloper.lastName": {
"type": "unified",
"pre_tags": [
"<name>"
],
"post_tags": [
"</name>"
],
"highlight_query": {
"match": {
"leadDeveloper.lastName": {
"query": "Stokes"
}
}
}
}
}
}
}
Handling Responses
editresponse.ShouldBeValid();
foreach (var highlightsInEachHit in response.Hits.Select(d => d.Highlights))
{
foreach (var highlightField in highlightsInEachHit)
{
if (highlightField.Key == "leadDeveloper.lastName")
{
foreach (var highlight in highlightField.Value.Highlights)
{
highlight.Should().Contain("<name>");
highlight.Should().Contain("</name>");
}
}
else
Assert.True(false, $"highlights contains unexpected key {highlightField.Key}");
}
}