Supporting typeahead autocomplete with ElasticSearch

Question

Is there a standard way to implement character-by-character typeahead autocomplete using ElasticSearch for small fields (e.g. place names).

(At the time of writing this, there are a number of discussions available via search, but nothing that seems definitive. (Also, I see there is talk of the effect of feature support for autocomplete/suggest in Apache Lucene 4.))

Thanks for thoughts.

Answer 1

You can use Edge NGram based analyzer, see http://www.elasticsearch.org/guide/reference/index-modules/analysis/edgengram-tokenizer.html

Or use the suggest plugin: https://github.com/spinscale/elasticsearch-suggest-plugin

HTH

Answer 2

As David wrote, you can use NGrams or the suggest plugin. With lucene 4 it will be possible to have better auto-suggestions out-of-the-box, without the need to mantain a separate index.

For now you can also just make a terms facet on your field and use a regex pattern to keep only the entries that start with the relevant prefix:

"facets" : {
    "tag" : {
        "terms" : {
            "field" : "field_name",
            "regex" : "prefix.*"
        }
    }
}

The regex is just an example, it can be improved and you can also make it case insensitive using the proper regex flag. Also, beware that making on a facet on a field that contains many unique terms is not a great idea, unless you have enough memory for it.