Elasticsearch NEST – Examples for mapping between Query and C#

During my training with Elasticsearch I would like to map a query with GET/POST method to C# syntax of NEST. It’s very helpful for me to see how NEST composes its internal queries and sends to Elasticsearch server. I just post my sample project here, maybe it’ll help you too.

1. Indexing Employee Documents

PUT /megacorp/employee/1{ "about": "I love to go rock climbing", "age": 25, "firstName": "John", "id": 1, "interests": [ "sports", "music" ], "lastName": "Smith"}

Employee employee = new Employee(){ Id = 1, FirstName = "John", LastName = "Smith", Age = 25, About = "I love to go rock climbing", Interests = new List<string>() { "sports", "music" }};await client.IndexAsync(employee);

2. Retrieving a Document

GET /megacorp/employee/1{ "_index" : "megacorp", "_type" : "employee", "_id" : "1", "_version" : 9, "found" : true, "_source" : { "about" : "I love to go rock climbing", "age" : 25, "firstName" : "John", "id" : 1, "interests" : [ "sports", "music" ], "lastName" : "Smith" }}

public async Task<T> GetById(int id){ var response = await client.GetAsync<T>(new DocumentPath<T>(id), g => g.Index(defaultIndex).Type(defaultType)); return response.Source;}

3. Search Lite

We will search for all employees, with this request

POST http://localhost:9200/megacorp/employee/_search?pretty=true{}

public async Task<IEnumerable<T>> SearchAsync(){ var response = await client.SearchAsync<T>(s => s.Type(defaultType)); return response.Documents;}

4. Search with Query DSL

We can represent the search for all Smiths like so

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "query": { "match": { "lastName": { "query": "Smith" } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.Match(m => m.Field(f => f.LastName).Query("Smith")))); Result = result.Documents;}

5. Search with Query String

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "query": { "query_string": { "query": "Smith", "fields": [ "lastName" ] } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.QueryString(qs => qs.Fields(f => f.Field(fi => fi.LastName)) .Query("Smith")))); Result = result.Documents;}

6. More-Complicated Searches

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "query": { "bool": { "must": [ { "match": { "lastName": { "query": "smith" } } } ], "filter": [ { "range": { "age": { "gt": 30.0 } } } ] } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.Bool(b => b.Filter(f => f.Range(r => r.Field(fi => fi.Age).GreaterThan(30))) .Must(m => m.Match(ma => ma.Field(fie => fie.LastName).Query("smith"))) ))); Result = result.Documents;}

7. Full-Text Search

We are going to search for all employees who enjoy “rock climbing”, “rock” or “climbing”.

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "query": { "match": { "about": { "query": "rock climbing" } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.Match(m => m.Field(f => f.About).Query("rock climbing")) )); Result = result.Documents;}

8. Phrase Search

Finding individual words in a field is all well and good, but sometimes you want to
match exact sequences of words or phrases. For instance, we could perform a query
that will match only employee records that contain both “rock” and “climbing” and
that display the words are next to each other in the phrase “rock climbing.”

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "query": { "match": { "about": { "type": "phrase", "query": "rock climbing" } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.MatchPhrase(m => m.Field(f => f.About).Query("rock climbing")) )); Result = result.Documents;}

9. Highlighting Our Searches

Many applications like to highlight snippets of text from each search result so the user
can see why the document matched the query

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "highlight": { "fields": { "about": {} } }, "query": { "match": { "about": { "type": "phrase", "query": "rock climbing" } } }}

10. Analytics

Let’s find the most popular interests enjoyed by our employees

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "aggs": { "all_interests": { "terms": { "field": "interests" } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Aggregations(a => a.Terms("all_interests", t => t.Field(f => f.Interests))) ); Result = result.Aggregations;}

11. Analytics limit

If we want to know the popular interests of people called Smith, we can just add the appropriate query into the mix:

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "aggs": { "all_interests": { "terms": { "field": "interests" } } }, "query": { "match": { "lastName": { "query": "smith" } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Query(q => q.Match(m => m.Field(fi => fi.LastName).Query("smith"))) .Aggregations(a => a.Terms("all_interests", t => t.Field(f => f.Interests))) ); Result = result.Aggregations;}

12. Analytics with Average

POST http://localhost:9200/megacorp/employee/_search?pretty=true{ "aggs": { "all_interests": { "terms": { "field": "interests" }, "aggs": { "avg_age": { "avg": { "field": "age" } } } } }}

public async Task ExecuteAsync(){ var result = await client.SearchAsync<Employee>( s => s.Type(typeEmployee) .Aggregations(a => a.Terms("all_interests", t => t.Field(f => f.Interests) .Aggregations(ag => ag.Average("avg_age", av => av.Field(fi => fi.Age))) ) ) ); Result = result.Aggregations;}

13. Retrieving Part of a Document

GET http://localhost:9200/website/blog/123?pretty=true&fields=title%2Ctext

public async Task ExecuteAsync(){ var response = await client.GetAsync(new DocumentPath<Blog>(123), g => g.Fields(f => f.Title, f => f.Text)); Result = response.Fields;}

14. Updating a Whole Document

PUT http://localhost:9200/website/blog/123?pretty=true{ "date": "2014-01-01T00:00:00", "id": 123, "text": "I am staring to get the hang of this...", "title": "My first blog entry"}

public async Task ExecuteAsync(){ var blog = new Blog() { Id = 123, Title = "My first blog entry", Text = "I am staring to get the hang of this...", Date = new DateTime(2014, 1, 1) }; Result = await client.UpdateAsync(new DocumentPath<Blog>(123), u => u.Doc(blog));}

15. Partial Updates to Documents

POST http://localhost:9200/website/blog/1/_update?pretty=true{ "doc": { "tags": [ "testing" ], "views": 0 }}

public async Task ExecuteAsync(){ var blog = new Blog() { Id = 1, Title = "My first blog entry", Text = "Just trying this out..." }; await client.IndexAsync(blog); dynamic dyn = new ExpandoObject(); dyn.Tags = new List<string>() { "testing" }; dyn.Views = 0; Result = await client.UpdateAsync<Blog, dynamic>(new DocumentPath<Blog>(1), u => u.Doc(dyn));}

16. Deleting a Document

DELETE http://localhost:9200/website/blog/123?pretty=true

public async Task ExecuteAsync(){ Result = await client.DeleteAsync(new DocumentPath<Blog>(123));}

17. Cluster Health

GET http://localhost:9200/_cluster/health?pretty=true

public async Task ExecuteAsync(){ Result = await client.ClusterHealthAsync();}

18. Add an Index

PUT http://localhost:9200/blogs?pretty=true{ "settings": { "index.number_of_replicas": 1, "index.number_of_shards": 3 }}

public async Task ExecuteAsync(){ Result = await client.CreateIndexAsync("blogs", c => c.Settings(s => s.NumberOfShards(3) .NumberOfReplicas(1)));}

19. Retrieving Part of a Document

GET http://localhost:9200/website/blog/123?pretty=true&_source_include=title%2Ctext

public async Task ExecuteAsync(){ Result = await client.GetAsync<Blog>(new DocumentPath<Blog>(123), g => g.SourceInclude("title", "text"));}

20. Using Versions from an External System

PUT http://localhost:9200/website/blog/2?pretty=true&version=25&version_type=external{ "date": "0001-01-01T00:00:00", "id": 0, "text": "Starting to get the hang of this...", "title": "My first external blog entry", "views": 0}

public async Task ExecuteAsync(){ var getResponse = (await client.GetAsync<Blog>(new DocumentPath<Blog>(2))); var blog = getResponse.Source; long version; if (blog == null) { blog = new Blog() { Title = "My first external blog entry", Text = "Starting to get the hang of this..." }; var result = await client.IndexAsync(blog, i => i.Id(2)); version = result.Version; } else version = getResponse.Version; Result = await client.IndexAsync(blog, i => i.Id(2).Version(version + 5).VersionType(VersionType.External));}

21. Using Scripts to Make Partial Updates

POST http://localhost:9200/website/blog/1/_update?pretty=true{ "script": "ctx._source.views += 1"}

public async Task ExecuteAsync(){ Result = await client.UpdateAsync(new DocumentPath<Blog>(1), u => u.Script("ctx._source.views += 1"));}

POST http://localhost:9200/website/blog/1/_update?pretty=true{ "script": "ctx._source.tags+=new_tag", "params": { "new_tag": "search" }}

public async Task ExecuteAsync(){ Result = await client.UpdateAsync(new DocumentPath<Blog>(1), u => u.Script("ctx._source.tags+=new_tag") .Params(p => p.Add("new_tag", "search")));}

POST http://localhost:9200/website/blog/1/_update?pretty=true{ "script": "ctx.op = ctx._source.views == count ? 'delete' : 'none'", "params": { "count": "1" }}

Result = await client.UpdateAsync(new DocumentPath<Blog>(1), u => u.Script("ctx.op = ctx._source.views == count ? 'delete' : 'none'") .Params(p => p.Add("count", "1")));

22. Updating a Document That May Not Yet Exist

Imagine that we need to store a page view counter in Elasticsearch. Every time that a user views a page, we increment the counter for that page. But if it is a new page, we can’t be sure that the counter already exists. If we try to update a nonexistent document, the update will fail.
In cases like these, we can use the upsert parameter to specify the document that should be created if it doesn’t already exist

POST http://localhost:9200/website/pageviews/1/_update?pretty=true{ "script": "ctx._source.views+=1", "upsert": { "id": 0, "views": 1 }}

public async Task ExecuteAsync(){ Result = await client.UpdateAsync(new DocumentPath<PageViews>(1), u => u.Script("ctx._source.views+=1") .Upsert(new PageViews() { Views = 1 }));}

23. Updates and Conflicts

POST http://localhost:9200/website/pageviews/1/_update?pretty=true&retry_on_conflict=5{ "script": "ctx._source.views+=1", "upsert": { "id": 1, "views": 0 }}

Result = await client.UpdateAsync(new DocumentPath<PageViews>(1), u => u.Script("ctx._source.views+=1") .Upsert(new PageViews { Id = 1, Views = 0 }) .RetryOnConflict(5));

24. Retrieving Multiple Documents

POST http://localhost:9200/_mget?pretty=true{ "docs": [ { "_index": "website", "_type": "blog", "_id": 2 }, { "_index": "website", "_type": "pageviews", "_id": 1 } ]}

public async Task ExecuteAsync(){ Result = await client.MultiGetAsync(m => m.Get<Blog>(g => g.Id(2)) .Get<PageViews>(ge => ge.Id(1)) );}

POST http://localhost:9200/website/blog/_mget?pretty=true{ "ids": [ 2, 1 ]}

Result = await client.MultiGetAsync(m => m.Index(indexWebsite) .Type(typeBlog) .GetMany<Blog>(new long[] { 2, 1 }));

100. Source code

Source code: https://bitbucket.org/hintdesk/dotnet-elasticsearch-nest-examples-for-mapping-between-query

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