Elasticsearch search fo words having '#' character - elasticsearch

Question

For example, I am right now searching like this:
http://localhost:9200/posts/post/_search?q=content:%23sachin
But, I am getting all the results with 'sachin' and not '#sachin'. Also, I am writing a regular expression for getting the count of terms. The facet looks like this:
"facets": {
"content": {
"terms": {
"field": "content",
"size": 1000,
"all_terms": false,
"regex": "#sachin",
"regex_flags": [
"DOTALL",
"CASE_INSENSITIVE"
]
}
}
}
This is not returning any values. I think it has something to do with escaping the '#' inside the regular expression, but I am not sure how to do it. I have tried to escape it \ and \\, but it did not work. Can anyone help me in this regard?

Answer 1

This article gives information on how save # and # using custom analyzers:
https://web.archive.org/web/20160304014858/http://www.fullscale.co/blog/2013/03/04/preserving_specific_characters_during_tokenizing_in_elasticsearch.html
curl -XPUT 'http://localhost:9200/twitter' -d '{
"settings" : {
"index" : {
"number_of_shards" : 1,
"number_of_replicas" : 1
},
"analysis" : {
"filter" : {
"tweet_filter" : {
"type" : "word_delimiter",
"type_table": ["# => ALPHA", "# => ALPHA"]
}
},
"analyzer" : {
"tweet_analyzer" : {
"type" : "custom",
"tokenizer" : "whitespace",
"filter" : ["lowercase", "tweet_filter"]
}
}
}
},
"mappings" : {
"tweet" : {
"properties" : {
"msg" : {
"type" : "string",
"analyzer" : "tweet_analyzer"
}
}
}
}
}'
This isn't dealing with facets, but the redefining of the type of those special characters in the analyzer could help.

Answer 2

Another approach that worth to consider is to index a special (e.g. "reserved") word instead of hash symbol. For example: HASHSYMBOLCHAR. Make sure that you will replace '#' chars in query as well.