Elasticsearch: Search for substring with index values in input value

Question

I have a special case for searching inside the elasticsearch. I also had a deep look into the documentation, tokenizer (n-gram, edge-ngram), queries etc. and the stackoverflow search, but without result.

Background I have a small index with some string fields (eq. name, street, city, email).

And a query like

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What I want is to search with the values from the index inside the query.

So if I have an entry in the index with name = "My-Name" or street = "My-Street" this entry should be returned.

The closest post which I could found was Search ElasticSearch field contained in a value, but the tokenizer just split the values from the index, i need more like a substring-search in the query.

Thanks and best regards Simon

Simon Simon · Accepted Answer · 2017-01-12T16:38:19

Found a possible (but not high-performance) solution:

1.) Set an n-gram filter only for the search-analyzer. Index-analyzer is still "standard":

setting:

"analysis": {
    "filter": {
        "desc_ngram": {
            "type": "ngram",
            "min_gram": 3,
            "max_gram": 50
        }
    },
    "analyzer": {
        "search_ngram": {
            "type": "custom",
            "tokenizer": "keyword",
            "filter": [ "desc_ngram", "lowercase" ]
        }
    }
}

mapping

"user": {
    "properties": {
        "street": {
            "type": "string",
            "analyzer": "standard",
            "search-analyzer": "search_ngram"
        }
    }...
}

2.)Split the input-text into small blocks (about 47 chars)

String subtext = request.post.getText().substring(startIndex, offset);

3.) Fire-up an ordinary query to the elasticsearch for each block (Do this in an asynchronous manner)

        return CompletableFuture.supplyAsync(() -> {

        SearchRequestBuilder search = this.prepareSearch()
                .setQuery(QueryBuilders.queryStringQuery(textToAnalyze))
                .setSize(100);

        SearchResponse response = search.get();
        UserHit result = transformToHitFrom(response, UserHit.class);
        return result;
    }).exceptionally(e -> {
        logger.error("Error occurred while searching for user", e);
        UserHit result = new UserHit();
        return result;
    });

I did not perform a performance-test yet, but I hope that this solution has a better performance than the standard substring method. We will test this in the following days.

Elasticsearch: Search for substring with index values in input value

1 Answers