這是ElasticSearch 2.4 版本系列的第五篇:
使用C#代碼實現(xiàn)對ElastiSearch的編程查詢,是十分方便的,通常情況下,開發(fā)者采用官方提供的NEST客戶端程序,通過封裝的方法向ElasticSearch引擎發(fā)送查詢請求,搜索數(shù)據(jù),最終獲取返回的查詢結(jié)果,實現(xiàn)預定的業(yè)務(wù)需求。在內(nèi)部,NEST客戶端通過格式化的數(shù)據(jù)結(jié)構(gòu),把C#代碼轉(zhuǎn)換成HTTP 請求(Request),減輕了用戶直接編寫Qeury DSL的麻煩。當然,用戶也可以直接把Query DSL封裝成HTTP請求,發(fā)送到ElasticSearch引擎;對開發(fā)者來說,不僅需要熟悉Query DSL的語法,而且需要手動編寫代碼,處理引擎返回的JSON結(jié)構(gòu)化的數(shù)據(jù)集,采用這種方式的優(yōu)點是不受限于NEST客戶端程序,能夠最大化使用ElasticSearch查詢的各種參數(shù),書寫自由。
本文簡單介紹使用C#代碼對ElasticSearch進行編程查詢的流程,具體的細節(jié),請參考官方文檔。
一,編程流程
1,創(chuàng)建客戶端
在搜索文檔之前,首先要連接到ElasticSearch引擎,創(chuàng)建客戶端對象
using Nest;var node = new Uri("http://myserver:9200");var settings = new ConnectionSettings(node).DefaultIndex("default");var client = new ElasticClient(settings);
2,創(chuàng)建查詢請求
連接到引擎之后,創(chuàng)建搜索請求(SearchRequest),用于封裝查詢類型和查詢條件
SearchRequest sr = new SearchRequest("meetup", "events");
3,指定查詢類型和查詢條件
為搜索請求指定查詢類型,可以是詞條搜索,或全文搜索
TermQuery tq = new TermQuery(); tq.Field = "eventname"; tq.Value = "azure"; sr.Query = tq;
4,調(diào)整查詢結(jié)果
為搜索請求設(shè)置參數(shù),排序,分頁,和選擇返回的字段等,在選擇查詢結(jié)果返回的字段時,推薦在查詢請求(SearchRequest)中使用Source Filter。
在查詢請求中,通過類RequestSearch的數(shù)組字段StoredFileds,把已存儲字段添加到該數(shù)組中,ElasticSearch引擎只返回特定的字段,而不是文檔的所有字段。在索引映射中,已存儲字段的store屬性為true,StoredFileds數(shù)組只能選擇已存儲字段(stored field)。
//windowssr.From = 0; sr.Size = 100;//sortISort sort = new SortField { Field = "eventid", Order = SortOrder.Ascending }; sr.Sort = new List<ISort>(); sr.Sort.Add(sort);//source filtersr.Source = new SourceFilter() { Includes = new string[] { "eventid", "eventname" }, Excludes = new string[] { "roginalid", "description" } };
5,執(zhí)行查詢請求
最后,客戶端執(zhí)行搜索請求,獲取搜索結(jié)果,并將查詢結(jié)果中的文檔集轉(zhuǎn)換成列表
var result = client.Search<MeetupEvents>(sr);return result.Documents.ToList<MeetupEvents>();
二,示例代碼,使用Nest客戶端搜索文檔
在該示例代碼中,本文簡單列舉詞條查詢,匹配查詢,布爾查詢和正則表達式查詢的示例代碼。
1,詞條查詢
public List<MeetupEvents>GetResult_TermQuery( ) { //create term query TermQuery tq = new TermQuery(); tq.Field = "eventname"; tq.Value = "azure"; //create search request SearchRequest sr = new SearchRequest("meetup", "events"); sr.Query = tq; //windows sr.From = 0; sr.Size = 100; //sort ISort sort = new SortField { Field = "eventid", Order = SortOrder.Ascending }; sr.Sort = new List<ISort>(); sr.Sort.Add(sort); //source filter sr.Source = new SourceFilter() { Includes = new string[] { "eventid", "eventname" }, Excludes = new string[] { "roginalid", "description" } }; var result = client.Search<MeetupEvents>(sr); return result.Documents.ToList<MeetupEvents>(); }
2,匹配查詢
public List<MeetupEvents> GetResult_MatchQuery() { SearchRequest sr = new SearchRequest("meetup", "events"); MatchQuery mq = new MatchQuery(); mq.Field = new Field("eventname"); mq.Query = "azure cloud"; mq.MinimumShouldMatch = 2; mq.Operator = Operator.Or; sr.Query = mq; sr.From = 0; sr.Size = 100; sr.Sort = new List<ISort>(); sr.Sort.Add(new SortField { Field = "eventid", Order = SortOrder.Ascending }); ISearchResponse<MeetupEvents> result = client.Search<MeetupEvents>(sr); return result.Documents.ToList<MeetupEvents>(); }
3,正則表達式查詢
public List<MeetupEvents>GetResult_RegexpQuery() { SearchRequest sr = new SearchRequest(); RegexpQuery rq = new RegexpQuery(); rq.Field = "description"; rq.Value = "azu.*"; rq.MaximumDeterminizedStates = 20000; sr.Query = rq; var result = client.Search<MeetupEvents>(sr); return result.Documents.ToList<MeetupEvents>(); }
4,布爾查詢
public List<MeetupEvents>GetResult_BoolQuery() { SearchRequest sr = new SearchRequest("meetup", "events"); BoolQuery bq = new BoolQuery(); bq.Filter = new QueryContainer[] { new MatchQuery() { Field="eventname", Query="azure cloud", Operator=Operator.Or, MinimumShouldMatch=1 }, new MatchQuery() { Field ="eventname", Query="aws google", Operator=Operator.Or, MinimumShouldMatch=1 } }; bq.Should = new QueryContainer[] { new TermQuery() { Field="description", Value="azure" }, new TermQuery() { Field="description", Value="cloud" } }; bq.MinimumShouldMatch = 1; sr.Query = bq; var result = client.Search<MeetupEvents>(sr); return result.Documents.ToList<MeetupEvents>(); }
三,把Query DSL封裝成HTTP Request
向ElasticSearch引擎發(fā)送Http請求,在http請求中指定查詢的類型和查詢條件,引擎在收到請求后執(zhí)行搜索,查詢結(jié)果以HTTP 響應(yīng)(Response)返回,開發(fā)者需要從Response返回的JSON結(jié)構(gòu)字符串中解析搜索結(jié)果。
1,封裝類庫
以下HTTP網(wǎng)絡(luò)編程代碼,是我們項目組一姐Amy的作品,謝謝Amy的分享,代碼可以進一步封裝,在此文中,僅僅作為演示:
View Code
2,執(zhí)行查詢
查詢的結(jié)果是JSON結(jié)構(gòu)的字符串,通常使用JObject和JToken類處理。
ESRequest es = new ElasticSearchNet.ESRequest("cia-sh-svr-sis3", "meetup", "events");string json_query = @"{ ""query"":{ ""match"":{ ""eventname"":""azure"" } } }";string strJsonResult=es.ExecuteQeury(json_query);
解析JSON的常用類庫是:
http://www.cnblogs.com/ljhdo/p/4550135.html