why elasticsearch can not search a document contains one word? - elasticsearch

Question

I am using default settings for one index, follow DSL is how to create the documents and searching.
### create index
PUT /mk_test
{
"settings": {
"number_of_shards": 1,
"number_of_replicas": 1
},
"mappings": {
"_doc": {
"properties": {
"nickName": {
"type": "text"
}
}
}
}
}
### get index
GET /mk_test/_mapping
### create document
POST /mk_test/_doc
{
"nickName": "C.BP"
}
### create document
POST /mk_test/_doc
{
"nickName": "BP"
}
### create document
POST /mk_test/_doc
{
"nickName": "C.B"
}
### create document
POST /mk_test/_doc
{
"nickName": "你好，中国"
}
now I have 4 document in mk_test index,
and I have 2 search query, give me different answers.
I want to query docs contains "中国"
GET /mk_test/_search
{
"query": {
"bool": {
"must": [
{"match_phrase": {"nickName": "中国"}}
]
}
}
}
server responses:
{
"took" : 0,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 1.5779729,
"hits" : [
{
"_index" : "mk_test",
"_type" : "_doc",
"_id" : "c2gwwX0BTkUG9klh1b8k",
"_score" : 1.5779729,
"_source" : {
"nickName" : "你好，中国"
}
}
]
}
}
I want to query docs contains "BP", I can't get "C.BP",
GET /mk_test/_search
{
"query": {
"bool": {
"must": [
{"match_phrase": {"nickName": "BP"}}
]
}
}
}
server give me only "BP", but "C.BP" not found
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 1.4599355,
"hits" : [
{
"_index" : "mk_test",
"_type" : "_doc",
"_id" : "TmguwX0BTkUG9klhAJ_S",
"_score" : 1.4599355,
"_source" : {
"nickName" : "BP"
}
}
]
}
}
How can I find both "BP" and "C.BP" ?