Scroll example in ElasticSearch NEST API
I am using .From() and .Size() methods to retrieve all documents from Elastic Search results.
Below is sample example -
ISearchResponse<dynamic> bResponse = ObjElasticClient.Search<dynamic>(s => s.From(0).Size(25000).Index("accounts").AllTypes().Query(Query));
Recently i came across scroll feature of Elastic Search. This looks better approach than From() and Size() methods specifically to fetch large data.
https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-scroll.html
I looking for example on Scroll feature in NEST API.
Can someone please provide NEST example?
Thanks, Sameer
Internal implementation of NEST Reindex uses scroll to move documents from one index to another.
It should be good starting point.
Below you can find interesting for you code from github.
var page = 0;
var searchResult = this.CurrentClient.Search<T>(
s => s
.Index(fromIndex)
.AllTypes()
.From(0)
.Size(size)
.Query(this._reindexDescriptor._QuerySelector ?? (q=>q.MatchAll()))
.SearchType(SearchType.Scan)
.Scroll(scroll)
);
if (searchResult.Total <= 0)
throw new ReindexException(searchResult.ConnectionStatus, "index " + fromIndex + " has no documents!");
IBulkResponse indexResult = null;
do
{
var result = searchResult;
searchResult = this.CurrentClient.Scroll<T>(s => s
.Scroll(scroll)
.ScrollId(result.ScrollId)
);
if (searchResult.Documents.HasAny())
indexResult = this.IndexSearchResults(searchResult, observer, toIndex, page);
page++;
} while (searchResult.IsValid && indexResult != null && indexResult.IsValid && searchResult.Documents.HasAny());
Also you can take a look at integration test for Scroll
[Test]
public void SearchTypeScan()
{
var scanResults = this.Client.Search<ElasticsearchProject>(s => s
.From(0)
.Size(1)
.MatchAll()
.Fields(f => f.Name)
.SearchType(SearchType.Scan)
.Scroll("2s")
);
Assert.True(scanResults.IsValid);
Assert.False(scanResults.FieldSelections.Any());
Assert.IsNotNullOrEmpty(scanResults.ScrollId);
var results = this.Client.Scroll<ElasticsearchProject>(s=>s
.Scroll("4s")
.ScrollId(scanResults.ScrollId)
);
var hitCount = results.Hits.Count();
while (results.FieldSelections.Any())
{
Assert.True(results.IsValid);
Assert.True(results.FieldSelections.Any());
Assert.IsNotNullOrEmpty(results.ScrollId);
var localResults = results;
results = this.Client.Scroll<ElasticsearchProject>(s=>s
.Scroll("4s")
.ScrollId(localResults.ScrollId));
hitCount += results.Hits.Count();
}
Assert.AreEqual(scanResults.Total, hitCount);
}
Here's an example of using scroll with NEST and C#. Works with 5.x and 6.x
public IEnumerable<T> GetAllDocumentsInIndex<T>(string indexName, string scrollTimeout = "2m", int scrollSize = 1000) where T : class
{
ISearchResponse<T> initialResponse = this.ElasticClient.Search<T>
(scr => scr.Index(indexName)
.From(0)
.Take(scrollSize)
.MatchAll()
.Scroll(scrollTimeout));
List<T> results = new List<T>();
if (!initialResponse.IsValid || string.IsNullOrEmpty(initialResponse.ScrollId))
throw new Exception(initialResponse.ServerError.Error.Reason);
if (initialResponse.Documents.Any())
results.AddRange(initialResponse.Documents);
string scrollid = initialResponse.ScrollId;
bool isScrollSetHasData = true;
while (isScrollSetHasData)
{
ISearchResponse<T> loopingResponse = this.ElasticClient.Scroll<T>(scrollTimeout, scrollid);
if (loopingResponse.IsValid)
{
results.AddRange(loopingResponse.Documents);
scrollid = loopingResponse.ScrollId;
}
isScrollSetHasData = loopingResponse.Documents.Any();
}
this.ElasticClient.ClearScroll(new ClearScrollRequest(scrollid));
return results;
}
It's from: http://telegraphrepaircompany.com/elasticsearch-nest-scroll-api-c/
链接地址: http://www.djcxy.com/p/86570.html