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1. 数据构造
索引2个文档到 hotel 索引中:
PUT /hotel/_doc/1 { "title": "文雅酒店", "city": "青岛", "price": 556, "create_time": "20200418120000", "amenities": "浴池,普通停车场/充电停车场", "full_room": false, "location": { "lat": 36.083078, "lon": 120.37566 }, "praise": 10 } PUT /hotel/_doc/2 { "title": "金都嘉怡假日酒店", "city": "北京", "price": 337, "create_time": "20210315200000", "amenities": "wifi,充电停车场/可升降停车场", "full_room": false, "location": { "lat": 39.915153, "lon": 116.403 }, "praise": 60 } PUT /hotel/_doc/1 { "title": "文雅酒店", "city": "青岛", "price": 556, "create_time": "20200418120000", "amenities": "浴池,普通停车场/充电停车场", "full_room": false, "location": { "lat": 36.083078, "lon": 120.37566 }, "praise": 10 } PUT /hotel/_doc/2 { "title": "金都嘉怡假日酒店", "city": "北京", "price": 337, "create_time": "20210315200000", "amenities": "wifi,充电停车场/可升降停车场", "full_room": false, "location": { "lat": 39.915153, "lon": 116.403 }, "praise": 60 }
2. ElasticSearch 查询集群中所有索引中的所有文档
GET /hotel/_search
{ "took" : 499, "timed_out" : false, "_shards" : { "total" : 5, "successful" : 5, "skipped" : 0, "failed" : 0 }, "hits" : { "total" : { "value" : 2, "relation" : "eq" }, "max_score" : 1.0, "hits" : [ { "_index" : "hotel", "_type" : "_doc", "_id" : "2", "_score" : 1.0, "_source" : { "title" : "金都嘉怡假日酒店", "city" : "北京", "price" : 337, "create_time" : "20210315200000", "amenities" : "wifi,充电停车场/可升降停车场", "full_room" : false, "location" : { "lat" : 39.915153, "lon" : 116.403 }, "praise" : 60 } }, { "_index" : "hotel", "_type" : "_doc", "_id" : "1", "_score" : 1.0, "_source" : { "title" : "文雅酒店", "city" : "青岛", "price" : 556, "create_time" : "20200418120000", "amenities" : "浴池,普通停车场/充电停车场", "full_room" : false, "location" : { "lat" : 36.083078, "lon" : 120.37566 }, "praise" : 10 } } ] } }
3. ElasticSearch 搜索结果字段解析
1. took 搜索请求耗费了多少毫秒
took值告诉我们执行整个搜索请求耗费了多少毫秒。
2. shards 查询中参与分片的总数
_shards部分告诉我们在查询中参与分片的总数,以及这些分片成功了多少个失败了多少个。正常情况下我们不希望分片失败,但是分片失败是可能发生的。如果我们遭遇到一种灾难级别的故障,在这个故障中丢失了相同分片的原始数据和副本,那么对这个分片将没有可用副本来对搜索请求作出响应。假若这样,Elasticsearch 将报告这个分片是失败的,但是会继续返回剩余分片的结果。
3. timed_out 查询是否超时
timed_out值告诉我们查询是否超时。默认情况下,搜索请求不会超时。
4. hits 表示搜索结果
返回结果中最重要的部分是
hits,它包含
total字段来表示匹配到的文档总数,并且一个
hits数组包含所查询结果的前十个文档。在解析搜索结果时,我们通常需要关注以下几个字段:
hits.total.value:匹配的文档总数。
hits.max_score:与查询所匹配文档的_score的最大值。
hits.hits:匹配的文档列表。
hits.hits._source:匹配的文档的原始数据。
hits.hits._score:匹配的文档的分数。它衡量了文档与查询的匹配程度,默认情况下,首先返回最相关的文档结果,就是说,返回的文档是按照score 降序排列的。
hits.hits.highlight:匹配的文档的高亮显示信息。
4. SpringBoot 整合ElasticSearch获取搜索结果
@Slf4j @Service public class ElasticSearchImpl { @Autowired private RestHighLevelClient restHighLevelClient; public void searchUser() throws IOException { SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder(); SearchRequest searchRequest = new SearchRequest(new String[]{"hotel"},searchSourceBuilder); SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT); TimeValue took = searchResponse.getTook(); System.out.println("took = " + took); // 搜索结果 SearchHits searchHits = searchResponse.getHits(); // hits.total.value:匹配的文档总数 TotalHits totalHits = searchHits.getTotalHits(); long value = totalHits.value; System.out.println("value = " + value); // hits.max_score:与查询所匹配文档的_score的最大值 float maxScore = searchHits.getMaxScore(); System.out.println("maxScore = " + maxScore); // hits.hits:匹配的文档列表 SearchHit[] hits = searchHits.getHits(); for (SearchHit hit : hits) { // hits.hits._source:匹配的文档的原始数据 String sourceAsString = hit.getSourceAsString(); System.out.println("sourceAsString = " + sourceAsString); // hits.hits._id:匹配的文档的id String id = hit.getId(); System.out.println("id = " + id); Map<String, DocumentField> fields = hit.getFields(); System.out.println("fields = " + fields); String index = hit.getIndex(); System.out.println("index = " + index); float score = hit.getScore(); System.out.println("score = " + score); } System.out.println(searchResponse); } } @Slf4j @Service public class ElasticSearchImpl { @Autowired private RestHighLevelClient restHighLevelClient; public void searchUser() throws IOException { SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder(); SearchRequest searchRequest = new SearchRequest(new String[]{"hotel"},searchSourceBuilder); SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT); TimeValue took = searchResponse.getTook(); System.out.println("took = " + took); // 搜索结果 SearchHits searchHits = searchResponse.getHits(); // hits.total.value:匹配的文档总数 TotalHits totalHits = searchHits.getTotalHits(); long value = totalHits.value; System.out.println("value = " + value); // hits.max_score:与查询所匹配文档的_score的最大值 float maxScore = searchHits.getMaxScore(); System.out.println("maxScore = " + maxScore); // hits.hits:匹配的文档列表 SearchHit[] hits = searchHits.getHits(); for (SearchHit hit : hits) { // hits.hits._source:匹配的文档的原始数据 String sourceAsString = hit.getSourceAsString(); System.out.println("sourceAsString = " + sourceAsString); // hits.hits._id:匹配的文档的id String id = hit.getId(); System.out.println("id = " + id); Map<String, DocumentField> fields = hit.getFields(); System.out.println("fields = " + fields); String index = hit.getIndex(); System.out.println("index = " + index); float score = hit.getScore(); System.out.println("score = " + score); } System.out.println(searchResponse); } }
took=2ms value = 2 maxScore = 1.0 sourceAsString = {"title":"金都嘉怡假日酒店","city":"北京","price":337,"create_time":"20210315200000","amenities":"wifi,充电停车场/可升降停车场","full_room":false,"location":{"lat":39.915153,"lon":116.403},"praise":60} id = 2 fields = {} index = hotel score = 1.0 sourceAsString = {"title":"文雅酒店","city":"青岛","price":556,"create_time":"20200418120000","amenities":"浴池,普通停车场/充电停车场","full_room":false,"location":{"lat":36.083078,"lon":120.37566},"praise":10} id = 1 fields = {} index = hotel score = 1.0
{ "took": 2, "timed_out": false, "_shards": { "total": 5, "successful": 5, "skipped": 0, "failed": 0 }, "hits": { "total": { "value": 2, "relation": "eq" }, "max_score": 1.0, "hits": [ { "_index": "hotel", "_type": "_doc", "_id": "2", "_score": 1.0, "_source": { "title": "金都嘉怡假日酒店", "city": "北京", "price": 337, "create_time": "20210315200000", "amenities": "wifi,充电停车场/可升降停车场", "full_room": false, "location": { "lat": 39.915153, "lon": 116.403 }, "praise": 60 } }, { "_index": "hotel", "_type": "_doc", "_id": "1", "_score": 1.0, "_source": { "title": "文雅酒店", "city": "青岛", "price": 556, "create_time": "20200418120000", "amenities": "浴池,普通停车场/充电停车场", "full_room": false, "location": { "lat": 36.083078, "lon": 120.37566 }, "praise": 10 } } ] } }
5 .ElasticSearch 搜索结果的面试题
1. ElasticSearch 搜索结果中的 _score 字段是什么意思?
答:_score 字段表示匹配文档的相关度得分,分数越高表示匹配度越高。
2. ElasticSearch 搜索结果中的 highlight 字段是什么意思?
答:highlight 字段表示匹配文档中被高亮显示的字段及其高亮显示的内容。
3. 如何获取 ElasticSearch 搜索结果中的总文档数?
答:可以通过 hits.total.value 字段获取匹配的文档总数。
4. 如何获取 ElasticSearch 搜索结果中的匹配文档列表?
答:可以通过 hits.hits 字段获取匹配的文档列表。
5. 如何获取 ElasticSearch 搜索结果中匹配文档的原始数据?
答:可以通过 hits.hits._source 字段获取匹配文档的原始数据。
6. 如何获取 ElasticSearch 搜索结果中匹配文档的高亮显示信息?
答:可以通过 hits.hits.highlight 字段获取匹配文档的高亮显示信息。
7. ElasticSearch 搜索结果中的 _shards 字段是什么意思?
答:_shards 字段表示搜索涉及的分片信息,包括总分片数、成功的分片数、跳过的分片数和失败的分片数。
8. ElasticSearch 搜索结果中的 took 字段是什么意思?
答:took 字段表示搜索耗时,单位为毫秒。