Improve Elasticsearch Performance

Contents

Overview

Some tips on how to improve / ensure good Elasticsearch performance.

Customize Field Mappings

If you don't need to search a field, don't index it:

{
    "field_name": {
        "type":     "string",
        "index":    "no"
    }
}

For fields you want to index, use the simplest analyzer, or maybe don't analyze at all. By default, string fields are analyzed as are the strings in any queries on this fields. The other option is not_analyzed - the field is indexed so it is searchable, but the value is indexed, as a single string, exactly as specified.

{
    "field_name": {
        "type":     "string",
        "index":    "not_analyzed"
    }
}

The other simple types (long, double, date, etc.) also accept the index parameter, but the only relevant values are no and not_analyzed because their values are never analyzed.

Alternately specify analyzer: For analyzed string fields specify which analyzer to apply both at search time and index time. By default, Elasticsearch uses the standard analyzer, but you can change this by specifying one of the built-in analyzers, such as whitespace, simple, or english.

{
    "tweet": {
        "type":     "string",
        "analyzer": "english"
    }
}

Disable The _source Field

_source contains the original JSON document alongside the indexed fields. This can be removed when creating the index:

PUT index_name -d '
{
    "mappings": {
        "_source": {
            "enabled": false
        }
    }
}

However, without _source we cannot:

  • View the source field (string) which matched a query, we can only identify the doc _id for the match.

  • Do on the fly highlighting.

  • Use the update, update_by_query and reindex APIs.

  • Upgrade an index to a new major version or repair index corruption automatically.

An expert-only feature is the ability to prune the contents of the _source field after the document has been indexed, but before the _source field is stored. Removing fields from the _source has similar downsides to disabling _source.

Disable the _all Field