Elasticsearch Postings highlighter Error - cannot highlight - elasticsearch

Question

I got the following errors when trying to search with posting highlighter:
{
"error": {
"root_cause": [
{
"type": "illegal_argument_exception",
"reason": "field 'author_name' was indexed without offsets, cannot highlight"
}
],
"type": "search_phase_execution_exception",
"reason": "all shards failed",
"phase": "query_fetch",
"grouped": true,
"failed_shards": [
{
"shard": 1,
"index": "post",
"node": "abc",
"reason": {
"type": "illegal_argument_exception",
"reason": "field 'author_name' was indexed without offsets, cannot highlight"
}
}
],
"caused_by": {
"type": "illegal_argument_exception",
"reason": "field 'author_name' was indexed without offsets, cannot highlight"
}
},
"status": 400
}
And here's my mapping:
{
"post": {
"mappings": {
"page": {
"_routing": {
"required": true
},
"properties": {
"author_name": {
"type": "text",
"store": true,
"index_options": "offsets",
"fields": {
"keyword": {
"type": "keyword"
}
},
"analyzer": "the_analyzer",
"search_analyzer": "the_search_analyzer"
},
"editor": {
"properties": {
"author_name": {
"type": "keyword"
}
}
}
}
},
"blog_post": {
"_routing": {
"required": true
},
"properties": {
"author_name": {
"type": "text",
"store": true,
"index_options": "offsets",
"fields": {
"keyword": {
"type": "keyword"
}
},
"analyzer": "the_analyzer",
"search_analyzer": "the_search_analyzer"
},
"editor": {
"properties": {
"author_name": {
"type": "keyword"
}
}
}
}
},
"comments": {
"_routing": {
"required": true
},
"_parent": {
"type": "blog_post"
},
"properties": {
"author_name": {
"type": "text",
"store": true,
"index_options": "offsets",
"fields": {
"keyword": {
"type": "keyword"
}
},
"analyzer": "the_analyzer",
"search_analyzer": "the_search_analyzer"
}
}
}
}
}
}
And my query:
GET post/article/_search?routing=cat
{
"query": {
"bool": {
"filter": {
"term": {
"category": "cat"
}
},
"must": [
{
"query_string": {
"query": "bill",
"fields": ["author_name"]
}
}]
}
},
"highlight": {
"fields": {
"author_name": {}
}
}
}
Elasticsearch version: 5.1.1
Lucence version: 6.3.0
When I did _update_by_query it works for a while, before failing again (after more data added).
I did some Googling, and found this issue on Elasticsearch repo:
https://github.com/elastic/elasticsearch/issues/8558, cmiiw, basically said that I need to have the same mapping for the same field name, on the same index. But I already did that, but I didn't know if my editor object, that has author_name can cause that issue.
Lucence code that throws that error:
https://github.com/apache/lucene-solr/blob/e2521b2a8baabdaf43b92192588f51e042d21e97/lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/FieldOffsetStrategy.java#L92
https://github.com/apache/lucene-solr/blob/e2521b2a8baabdaf43b92192588f51e042d21e97/lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/FieldHighlighter.java#L162
Question: how do I fix this error? thanks