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
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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
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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;
}
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3. Search Lite
We will search for all employees, with this request
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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;
}
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4. Search with Query DSL
We can represent the search for all Smiths like so
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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
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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
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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”.
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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
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POST http://localhost:9200/megacorp/employee/_search?pretty=true
{
"highlight": {
"fields": {
"about": {}
}
},
"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")))
.Highlight(h => h.Fields(fi => fi.Field(fie => fie.About)))
);
Result = result.Hits;
}
|
10. Analytics
Let’s find the most popular interests enjoyed by our employees
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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
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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
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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
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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"
}
|
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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));
}
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15. Partial Updates to Documents
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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));
}
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16. Deleting a Document
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DELETE http://localhost:9200/website/blog/123?pretty=true
|
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public async Task ExecuteAsync()
{
Result = await client.DeleteAsync(new DocumentPath<Blog>(123));
}
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17. Cluster Health
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GET http://localhost:9200/_cluster/health?pretty=true
|
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public async Task ExecuteAsync()
{
Result = await client.ClusterHealthAsync();
}
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18. Add an Index
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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
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GET http://localhost:9200/website/blog/123?pretty=true&_source_include=title%2Ctext
|
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public async Task ExecuteAsync()
{
Result =
await client.GetAsync<Blog>(new DocumentPath<Blog>(123), g =>
g.SourceInclude("title", "text"));
}
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20. Using Versions from an External System
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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));
}
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21. Using Scripts to Make Partial Updates
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POST http://localhost:9200/website/blog/1/_update?pretty=true
{
"script": "ctx._source.views += 1"
}
|
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public async Task ExecuteAsync()
{
Result = await client.UpdateAsync(new DocumentPath<Blog>(1), u =>
u.Script("ctx._source.views += 1"));
}
|
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POST http://localhost:9200/website/blog/1/_update?pretty=true
{
"script": "ctx._source.tags+=new_tag",
"params": {
"new_tag": "search"
}
}
|
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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")));
}
|
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POST http://localhost:9200/website/blog/1/_update?pretty=true
{
"script": "ctx.op = ctx._source.views == count ? ‘delete‘ : ‘none‘",
"params": {
"count": "1"
}
}
|
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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")));
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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
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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 }));
}
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23. Updates and Conflicts
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POST http://localhost:9200/website/pageviews/1/_update?pretty=true&retry_on_conflict=5
{
"script": "ctx._source.views+=1",
"upsert": {
"id": 1,
"views": 0
}
}
|
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Result = await client.UpdateAsync(new DocumentPath<PageViews>(1), u =>
u.Script("ctx._source.views+=1")
.Upsert(new PageViews { Id = 1, Views = 0 })
.RetryOnConflict(5));
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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))
);
}
|
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POST http://localhost:9200/website/blog/_mget?pretty=true
{
"ids": [
2,
1
]
}
|
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Result = await client.MultiGetAsync(m =>
m.Index(indexWebsite)
.Type(typeBlog)
.GetMany<Blog>(new long[] { 2, 1 }));
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100. Source code
Source code: https://bitbucket.org/hintdesk/dotnet-elasticsearch-nest-examples-for-mapping-between-query
My strongly recommended books to read. Choose one and enjoy yourself.
时间： 2024-12-08 13:12:32
