使用 NEST 使用 linq 查询弹性搜索

Question

Is there any way to query Elasticsearch with NEST client using linq or lambda expressions.

I Want to do somthing like this:

client.Search<MyClass>(s => s.MyProperty.Contains("value") &&
                            (s.MySecondProperty == 123 ||
                             s.ThirdProperty > 12)) ;

Or

var query = from m in MyContext.MyClass
            where ...
            select m

I read a little about ElasticLinq but it seems that it is no more active. the last nuget package were published on october 2015

What i want to do is to create a method that get an Expression as parameter from the caller and search on elastic with it. the caller should not depend on ES or NEST API

Answer 1

In short, no.

The longer answer is, ElasticLINQ is the closest to a LINQ provider that I'm aware of but does not expose all of the capabilities of the Elasticsearch API.

Whilst there is some overlap between LINQ , IQueryable<T> et. al, and the search capabilities exposed by the Elasticsearch query DSL and REST API, there are many queries that cannot be easily expressed with LINQ eg what would a completion suggester query look like, or a function score query or a moving average aggregation using Holt-Winters ?

You would need to extend the methods available in LINQ and write a non-trivial query provider, all for the desire to fit a well defined query DSL into the LINQ paradigm.

Personally, I would be inclined to embrace the query DSL and REST API and look to transform your Expression into something that you can send with NEST, Elasticsearch.Net or HttpClient . The caller still doesn't need to know how the request is made.

If you do end up writing a LINQ query provider, I'd be very interested :)

Answer 2

The exact query you write there today works just great in ElasticLINQ.

The project is still alive - just sometimes there is no reason for a new release. There was a point release today to fix a corner case in generating Queries (not filters) using OR's nested within an AND.

Answer 3

I am currently working on the LINQ query provider library to generate NEST method calls. If someone is interested - here is the link to the GitHub repository - https://github.com/VladislavRybnikov/NEST.Linq