ElasticSearch Highlighting Not highlighting - elasticsearch

Question

I'm having difficulty understanding how to get highlighting to work.
My queries are returning the item, but I do not see the tags that would cause the highlight.
Here's the set up for the test index:
curl -XPUT 'http://localhost:9200/testfoo' -d '{
"mappings": {
"entry": {
"properties": {
"id": { "type": "integer" },
"owner": { "type": "string" },
"target": {
"properties": {
"id": { "type": "integer" },
"type": {
"type": "string",
"index": "not_analyzed"
}
}
},
"body": { "type": "string" },
"body_plain": { "type": "string"}
}
}
}
}'
Here's a couple of inserted documents:
curl -XPUT 'http://localhost:9200/testfoo/entry/1' -d'{
"id": 1,
"owner": "me",
"target": {
"type": "event",
"id": 100
},
"body": "<div>Message One has foobar in it</div>",
"body_plain": "Message One has foobar in it"
}'
curl -XPUT 'http://localhost:9200/testfoo/entry/2' -d'{
"id": 2,
"owner": "me",
"target": {
"type": "event",
"id": 200
},
"body": "<div>Message One has no bar in it</div>",
"body_plain": "Message One has no bar in it"
}'
A Simple search returns the expected document:
curl -XPOST 'http://localhost:9200/testfoo/_search?pretty' -d '{
"query": {
"simple_query_string": {
"query": "foobar"
}
}
}'
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 0.09492774,
"hits" : [ {
"_index" : "testfoo",
"_type" : "entry",
"_id" : "1",
"_score" : 0.09492774,
"_source" : {
"id" : 1,
"owner" : "me",
"target" : {
"type" : "event",
"id" : 100
},
"body" : "<div>Message One has foobar in it</div>",
"body_plain" : "Message One has foobar in it"
}
} ]
}
}
However, when I add "highlighting" I get the same JSON but body_plain is not "highlighted" with the matching term:
curl -XPOST 'http://localhost:9200/testfoo/_search?pretty' -d '{
"query":{
"query": {
"simple_query_string":{
"query":"foobar"
}
}
},
"highlight": {
"pre_tags": [ "<div class=\"highlight\">" ],
"post_tags": [ "</div>" ],
"fields": {
"_all": {
"fragment_size": 10,
"number_of_fragments": 1
}
}
},
"sort": [
"_score"
],
"_source": [ "target", "id", "body_plain", "body" ],
"min_score": 0.9,
"size":10
}'
{
"took" : 2,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 1.0,
"hits" : [ {
"_index" : "testfoo",
"_type" : "entry",
"_id" : "1",
"_score" : 1.0,
"_source" : {
"id" : 1,
"body" : "<div>Message One has foobar in it</div>",
"target" : {
"id" : 100,
"type" : "event"
},
"body_plain" : "Message One has foobar in it"
}
} ]
}
}
Where I was expecting body_plain to look like
Message One has <div class="highlight">foobar</div> in it
Wondering what I'm doing wrong. Thanks.

Answer 1

From the official documentation
In order to perform highlighting, the actual content of the field is
required. If the field in question is stored (has store set to true in
the mapping) it will be used, otherwise, the actual _source will be
loaded and the relevant field will be extracted from it.
The _all field cannot be extracted from _source, so it can only be
used for highlighting if it mapped to have store set to true.
You have two ways to solve this. Either you change your mapping to store the _all field:
{
"mappings": {
"entry": {
"_all": { <-- add this
"store": true
},
"properties": {
...
Or you change your query to this:
curl -XPOST 'http://localhost:9200/testfoo/_search?pretty' -d '{
"query":{
"query": {
"simple_query_string":{
"query":"foobar"
}
}
},
"highlight": {
"pre_tags": [ "<div class=\"highlight\">" ],
"post_tags": [ "</div>" ],
"require_field_match": false, <-- add this
"fields": {
"*": { <-- use this
"fragment_size": 10,
"number_of_fragments": 1
}
}
},
"sort": [
"_score"
],
"_source": [ "target", "id", "body_plain", "body" ],
"min_score": 0.9,
"size":10
}'