Elastic Search Query with # (at sign) bring the same as without - elasticsearch

Question

I'm trying to match text with an "#" prefix, e.g. "#stackoverflow" on ElasticSearch. I'm using a boolean query, and both these return the exact same results and actually ignore my # sign:
Query 1 with #:
{"query":{"bool":{"must":[{"query_string":{"default_field":"text","default_operator":"AND","query":"#stackoverflow"}}]}},"size":20}
Query 2 without:
{"query":{"bool":{"must":[{"query_string":{"default_field":"text","default_operator":"AND","query":"stackoverflow"}}]}},"size":20}
My Mapping:
{"posts":{"mappings":{"post":{"properties":{"upvotes":{"type":"long"},"created_time":{"type":"date","format":"strict_date_optional_time||epoch_millis"},"ratings":{"type":"long"},"link":{"type":"string"},"pic":{"type":"string"},"text":{"type":"string"},"id":{"type":"string"}}}}}}
I've tried encoding it to \u0040 but that didn't do any difference.

Answer 1

Your text field is of type text and is analyzed by default by the standard analyzer, which means that #stackoverflow will be indexed as stackoverflow after the analysis process, as can be seen below
GET /_analyze?analyzer=standard&text=#stackoverflow
{
"tokens": [
{
"token": "stackoverflow",
"start_offset": 1,
"end_offset": 14,
"type": "<ALPHANUM>",
"position": 0
}
]
}
You probably want to either use the keyword type if you need exact matching or specify a different analyzer, such as whitespace, which will preserve the # sign in your data:
GET /_analyze?analyzer=whitespace&text=#stackoverflow
{
"tokens": [
{
"token": "#stackoverflow",
"start_offset": 0,
"end_offset": 14,
"type": "word",
"position": 0
}
]
}
UPDATE:
Then I suggest using a custom analyzer for that field so you can control how the values are indexed. Recreate your index like this and then you should be able to do your searches:
PUT posts
{
"settings": {
"index": {
"analysis": {
"analyzer": {
"my_analyzer": {
"type": "custom",
"tokenizer": "whitespace",
"filter": [ "lowercase" ]
}
}
}
}
},
"mappings": {
"post": {
"properties": {
"upvotes": {
"type": "long"
},
"created_time": {
"type": "date",
"format": "strict_date_optional_time||epoch_millis"
},
"ratings": {
"type": "long"
},
"link": {
"type": "string"
},
"pic": {
"type": "string"
},
"text": {
"type": "string",
"analyzer": "my_analyzer"
},
"id": {
"type": "string"
}
}
}
}
}