CODEWITHSUNDEEP
elasticsearch
Henley Wing Chiu
Henley Wing Chiu

Reputation: 22535

ElasticSearch: mappings for fields that are sorted often

Suppose I have a field "epoch_date" that will be sorted often when I do Elastic Search queries. How should I map this field? Right now, I just have stored: yes. Should I index it even though this field will not count towards the relevancy scoring? What should I add to this field if I intend to sort on this field often, so it will be more efficient?

{
    "tweet" : {
        "properties" : {
            "epoch_date" : {
                "type" : "integer",
                "store" : "yes"
            }
        }
    }
}

Upvotes: 3

Views: 1937

Answers (2)

javanna
javanna

Reputation: 60225

There's nothing you need to change to sort on the field given your mapping. You can only sort on a field if it's indexed, and the default is "index":"yes" for numeric or dates. You can not set a numeric type to analyzed, since there's no text to analyze. Also, better to use the date type for a date instead of the integer.

Sorting can be memory expensive if your field you are sorting on has a lot of unique terms. Just make sure you have enough memory for it. Also, keep in mind that sorting on a specific field you throw away the relevance ranking, which is a big part of what a search engine is all about.

Whether you want to store the field too doesn't have anything to do with sorting, but just with the way you retrieve it in order to return it together with your search results. If you use the _source field (default behaviour) there's no reason to store specific fields. If you ask for specific fields using the fields option when querying, then the stored fields would be retrieved directly from lucene rather than extracted from the _source field parsing the json.

Upvotes: 4

Geert-Jan
Geert-Jan

Reputation: 18915

An index is used for efficient sorting. So YES, you want to create an index for the field.

As to needing it to be "more efficient", I'd kindly advise you to first check your results and see if they're fast enough. I don't see a reason beforehand (with the limited info you provided) to think it wouldn't be efficient.

If you intend to filter on the field as well (date-ranges?) be sure to use filters instead of queries whenever you feel the filters used will be used often. This because filters can be efficiently cached.

Upvotes: 0

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