How to match on prefix in Elasticsearch

Question

let's say that in my elasticsearch index I have a field called "dots" which will contain a string of punctuation separated words (e.g. "first.second.third").

I need to search for e.g. "first.second" and then get all entries whose "dots" field contains a string being exactly "first.second" or starting with "first.second.".

I have a problem understanding how the text querying works, at least I have not been able to create a query which does the job.

Answer 1

Elasticsearch has Path Hierarchy Tokenizer that was created exactly for such use case. Here is an example of how to set it for your index:

# Create a new index with custom path_hierarchy analyzer 
# See http://www.elasticsearch.org/guide/reference/index-modules/analysis/pathhierarchy-tokenizer.html
curl -XPUT "localhost:9200/prefix-test" -d '{
    "settings": {
        "analysis": {
            "analyzer": {
                "prefix-test-analyzer": {
                    "type": "custom",
                    "tokenizer": "prefix-test-tokenizer"
                }
            },
            "tokenizer": {
                "prefix-test-tokenizer": {
                    "type": "path_hierarchy",
                    "delimiter": "."
                }
            }
        }
    },
    "mappings": {
        "doc": {
            "properties": {
                "dots": {
                    "type": "string",
                    "analyzer": "prefix-test-analyzer",
                    //"index_analyzer": "prefix-test-analyzer", //deprecated
                    "search_analyzer": "keyword"
                }
            }
        }
    }
}'
echo
# Put some test data
curl -XPUT "localhost:9200/prefix-test/doc/1" -d '{"dots": "first.second.third"}'
curl -XPUT "localhost:9200/prefix-test/doc/2" -d '{"dots": "first.second.foo-bar"}'
curl -XPUT "localhost:9200/prefix-test/doc/3" -d '{"dots": "first.baz.something"}'
curl -XPOST "localhost:9200/prefix-test/_refresh"
echo
# Test searches. 
curl -XPOST "localhost:9200/prefix-test/doc/_search?pretty=true" -d '{
    "query": {
        "term": {
            "dots": "first"
        }
    }
}'
echo
curl -XPOST "localhost:9200/prefix-test/doc/_search?pretty=true" -d '{
    "query": {
        "term": {
            "dots": "first.second"
        }
    }
}'
echo
curl -XPOST "localhost:9200/prefix-test/doc/_search?pretty=true" -d '{
    "query": {
        "term": {
            "dots": "first.second.foo-bar"
        }
    }
}'
echo
curl -XPOST "localhost:9200/prefix-test/doc/_search?pretty=true&q=dots:first.second"
echo

Answer 2

There is also a much easier way, as pointed out in elasticsearch documentation:

just use:

{
    "text_phrase_prefix" : {
        "fieldname" : "yourprefix"
    }
}

or since 0.19.9:

{
    "match_phrase_prefix" : {
        "fieldname" : "yourprefix"
    }
}

instead of:

{   
    "prefix" : { 
        "fieldname" : "yourprefix" 
}