数据聚合

一、聚合的种类

官方文档 => 聚合 https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations.html
聚合：对文档信息的统计、分类、运算。类似mysql sum、avg、count

桶（Bucket）聚合：用来对文档做分组
- TermAggregation：按照文档字段值分组（相当于mysql group by）
- Date Histogram：按照日期阶梯分组，例如一周一组，一月一组
度量（metric）聚合：用来计算一些值，最大值、平均值、最小值等。
- Avg：平均值
- Max：最大值
- Min：最小值
- Stats：同时求max、min、avg、sum等
管道（pipeline）聚合：以其他聚合结果为基础继续做集合

二、DSL实现聚合

1、Bucket（桶）聚合

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_count：默认是按照文档数量的降序排序

GET /hotel/_search
{"size": 0,"aggs": {"brandAgg": {"terms": {"field": "brand","size": 20,"order": {"_count": "asc"}}}}
}

上面使用的bucket聚合，会扫描索引库所有的文档进行聚合。可以限制扫描的范围：利用query条件即可。

GET /hotel/_search
{"query": {"range": {"price": {"lt": 200 # 只对价位低于200的聚合}}}, "size": 0,"aggs": {"brandAgg": {"terms": {"field": "brand","size": 20,"order": {"_count": "asc"}}}}
}

2、Metrics（度量）聚合

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聚合的嵌套，先对外层进行聚合，在对内存进行聚合
注意嵌套查询：写在外层查询括号内，而非并立。

GET /hotel/_search
{"size": 0,"aggs": {"brandAgg": {"terms": {"field": "brand","size": 10,"order": {"scoreAgg.avg": "asc"}},"aggs": {"scoreAgg": {"stats": {"field": "score"}}}}}
}

三、RestAPI实现聚合

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bucket trem聚合（group by），实现品牌、星级、城市聚合的方法

    public Map<String, List<String>> filters(RequestParam requestParam) {String[] aggNames = new String[]{"brand","city","starName"};Map<String, List<String>> resultMap = new HashMap<>();SearchRequest searchRequest = new SearchRequest("hotel");// 限定聚合范围BoolQueryBuilder boolQueryBuilder = getBoolQueryBuilder(requestParam);searchRequest.source().query(boolQueryBuilder);// 聚合字段searchRequest.source().size(0);searchRequest.source().aggregation(AggregationBuilders.terms(aggNames[0]).field("brand").size(100));searchRequest.source().aggregation(AggregationBuilders.terms(aggNames[1]).field("city").size(100));searchRequest.source().aggregation(AggregationBuilders.terms(aggNames[2]).field("starName").size(100));try {SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);Aggregations aggregations = searchResponse.getAggregations();for (String aggName : aggNames) {Terms terms =  aggregations.get(aggName);List<String> list = new ArrayList<>();for (Terms.Bucket bucket : terms.getBuckets()) {list.add(bucket.getKeyAsString());}resultMap.put(aggName,list);}return resultMap;} catch (IOException e) {e.printStackTrace();return null;}}

自动补全

一、拼音分词器

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下载拼音分词器：https://github.com/medcl/elasticsearch-analysis-pinyin/releases/tag/v8.6.0
解压放在plugins目录下（docker挂载的目录），然后重启es
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二、自定义分词器

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拼音分词器的过滤规则，参照上面下载的链接。
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创建一个自定义分词器（text index库），分词器名：my_analyzer

// 自定义拼音分词器 + mapping约束
PUT /test
{"settings": {"analysis": {"analyzer": {"my_analyzer": {"tokenizer": "ik_max_word","filter": "py"}},"filter": {"py": {"type": "pinyin","keep_full_pinyin": false,"keep_joined_full_pinyin": true,"keep_original": true,"limit_first_letter_length": 16,"remove_duplicated_term": true,"none_chinese_pinyin_tokenize": false}}}},"mappings": {"properties": {"name": {"type": "text","analyzer": "my_analyzer","search_analyzer": "ik_smart"}}}
}

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三、自动补全查询

completion suggester查询：

字段类型必须是completion
字段值是多词条的数组才有意义

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// 自动补全的索引库
PUT test2
{"mappings": {"properties": {"title":{"type": "completion"}}}
}
// 示例数据
POST test2/_doc
{"title": ["Sony", "WH-1000XM3"]
}
POST test2/_doc
{"title": ["SK-II", "PITERA"]
}
POST test2/_doc
{"title": ["Nintendo", "switch"]
}// 自动补全查询
POST /test2/_search
{"suggest": {"title_suggest": {"text": "s", // 关键字"completion": {"field": "title", // 补全字段"skip_duplicates": true, // 跳过重复的"size": 10 // 获取前10条结果}}}
}

四、实现搜索款自动补全（例酒店信息）

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构建索引库

// 酒店数据索引库
PUT /hotel
{"settings": {"analysis": {"analyzer": {"text_anlyzer": {"tokenizer": "ik_max_word","filter": "py"},"completion_analyzer": {"tokenizer": "keyword","filter": "py"}},"filter": {"py": {"type": "pinyin","keep_full_pinyin": false,"keep_joined_full_pinyin": true,"keep_original": true,"limit_first_letter_length": 16,"remove_duplicated_term": true,"none_chinese_pinyin_tokenize": false}}}},"mappings": {"properties": {"id":{"type": "keyword"},"name":{"type": "text","analyzer": "text_anlyzer","search_analyzer": "ik_smart","copy_to": "all"},"address":{"type": "keyword","index": false},"price":{"type": "integer"},"score":{"type": "integer"},"brand":{"type": "keyword","copy_to": "all"},"city":{"type": "keyword"},"starName":{"type": "keyword"},"business":{"type": "keyword","copy_to": "all"},"location":{"type": "geo_point"},"pic":{"type": "keyword","index": false},"all":{"type": "text","analyzer": "text_anlyzer","search_analyzer": "ik_smart"},"suggestion":{"type": "completion","analyzer": "completion_analyzer"}}}
}

查询测试

GET /hotel/_search
{"query": {"match_all": {}}
}GET /hotel/_search
{"suggest": {"YOUR_SUGGESTION": {"text": "s","completion": {"field": "suggestion","skip_duplicates": true // 跳过重复的}}}
}

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    public List<String> getSuggestion(String prefix) {SearchRequest request = new SearchRequest("hotel");ArrayList<String> list = new ArrayList<>();try {request.source().suggest(new SuggestBuilder().addSuggestion("OneSuggestion",SuggestBuilders.completionSuggestion("suggestion").prefix(prefix).skipDuplicates(true).size(10)));SearchResponse response = restHighLevelClient.search(request, RequestOptions.DEFAULT);Suggest suggest = response.getSuggest();CompletionSuggestion oneSuggestion = suggest.getSuggestion("OneSuggestion");List<CompletionSuggestion.Entry.Option> options = oneSuggestion.getOptions();for (CompletionSuggestion.Entry.Option option : options) {String text = option.getText().toString();list.add(text);}} catch (IOException e) {e.printStackTrace();}return list;}