Elasticsearch match_phrase_prefix change between 6.6.2 and 6.7.0

match_phrase_prefix.txt

# Start Elasticsearch 6.6.2
docker run -p 9200:9200 docker.elastic.co/elasticsearch/elasticsearch-oss:6.6.2

# 1. Create an index with a mapping
curl -X PUT "http://localhost:9200/my-index?pretty" -H 'Content-Type: application/json' -d'{
  "settings": {
    "index": {
      "number_of_shards": 1,
      "number_of_replicas": 0
    }
  },
  "mappings": {
    "_doc": {
      "properties": {
        "title": {
          "type": "keyword",
          "fields": {
            "fulltext": {
              "type": "text"
            }
          },
          "ignore_above": 255
        }
      }
    }
  }
}'
# Response
{
  "acknowledged" : true,
  "shards_acknowledged" : true,
  "index" : "my-index"
}

# ------------------
# 2. Create a document
#
curl -X PUT "http://localhost:9200/my-index/_doc/1" -H 'Content-Type: application/json' -d '{ "title": "UPPER CASE TITLE" }'
# Response
{"_index":"my-index","_type":"_doc","_id":"1","_version":1,"result":"created","_shards":{"total":1,"successful":1,"failed":0},"_seq_no":0,"_primary_term":1}

# ------------------
# 3. Search 
curl -XGET 'http://localhost:9200/my-index/_doc/_search?pretty' -H 'Content-Type: application/json' -d '{"from":0,"size":10,"query":{"match_phrase_prefix":{"title":{"query":"UPPER","slop":0,"max_expansions":50,"boost":1.0}}},"_source":{"includes":["_id"],"excludes":[]}}'
# Response in 6.6.2 -> No hit
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 0,
    "max_score" : null,
    "hits" : [ ]
  }
}

# Now stop elasticsearch and start a 6.7.0 
docker run -p 9200:9200 docker.elastic.co/elasticsearch/elasticsearch-oss:6.7.0

# Play command 1, 2 and 3, the search result contains a hit
{
  "took" : 90,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 0.2876821,
    "hits" : [
      {
        "_index" : "my-index",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 0.2876821,
        "_source" : { }
      }
    ]
  }
}