Elastic search - no hit though there should be result - elasticsearch

Question

I've encountered the following problem with Elastic search, does anyone know where should I troubleshoot?
I'm happily retrieving result with the following query:
{
"query" : {
"match" : { "name" : "A1212001" }
}
}
But when I refine the value of the search field "name" to a substring, i've not no hit?
{
"query" : {
"match" : { "name" : "A12120" }
}
}
"A12120" is a substring of already hit query "A1212001"

Answer 1

If you don't have too many documents, you can go with a regexp query
POST /index/_search
{
"query" :{
"regexp":{
"name": "A12120.*"
}
}
}
or even a wildcard one
POST /index/_search
{
"query": {
"wildcard" : { "name" : "A12120*" }
}
}
However, as #Waldemar suggested, if you have many documents in your index, the best approach for this is to use an EdgeNGram tokenizer since the above queries are not ultra-performant.
First, you define your index settings like this:
PUT index
{
"settings" : {
"analysis" : {
"analyzer" : {
"my_analyzer" : {
"type": "custom",
"tokenizer" : "edge_tokens",
"filter": ["lowercase"]
}
},
"tokenizer" : {
"edge_tokens" : {
"type" : "edgeNGram",
"min_gram" : "1",
"max_gram" : "10",
"token_chars": [ "letter", "digit" ]
}
}
}
},
"mappings": {
"my_type": {
"properties": {
"name": {
"type": "string",
"analyzer": "my_analyzer",
"search_analyzer": "standard"
}
}
}
}
}
Then, when indexing a document whose name field contains A1212001, the following tokens will be indexed: A, A1, A12, A121, A1212, A12120, A121200, A1212001. So when you'll search for A12120 you'll find a match.

Answer 2

Are you using a Match Query this query will check for terms inside lucene and your term is A1212001 if you need to find a part of your term do you can use a Regex Query but you need know that will be there some internal impacts using regex because the shard will check in all of your terms.
If you need a more "professional" way to search a part of a term do you can use NGrams