Elasticsearch查詢常見問題

1、實現(xiàn)mysql中的like查詢效果

使用 NGram 分詞器作為字段的分詞器，可在索引創(chuàng)建時指定，也可以更新映射關(guān)系，以下展示如何在索引創(chuàng)建時指定 NGram 分詞器。

{
  "settings": {
    "analysis": {
      "analyzer": {
        "ngram_analyzer": {
          "tokenizer": "ngram_tokenizer"
        }
      },
      "tokenizer": {
        "ngram_tokenizer": {
          "type": "ngram",
          "min_gram": 1,
          "max_gram": 30,
          "token_chars": [
            "letter",
            "digit"
          ]
        }
      }
    }
  },
  "mappings": {
        "_default_": {
            "properties": {
                "Name": {
                    "type": "string",
                    "analyzer": "ngram_analyzer"
                }
            }
        }
    }
}

2、當(dāng)需要在一個字段上同時進行模糊查詢、排序時

可以指定2個分詞器

"mappings": {
        "_default_": {
            "properties": {
                "Name": {
                    "type": "string",
                    "analyzer": "ngram_analyzer",
                    "fields": {
                        "raw": {
                            "type": "keyword"                       }
                    }
                }
            }
        }
    }

對Name.raw進行排序

3、解決 Elasticsearch 超過 10000 條無法查詢的問題

方法一：重建索引，修改最大顯示數(shù)據(jù)大小

具體操作命令，如下（比如，設(shè)置可查詢 200000000 條數(shù)據(jù)，其中 alarm 是index名稱）：

PUT alarm/_settings
{ 
  "max_result_window" : 200000000
}

方法二：使用es自帶的scroll分頁支持

初始化查詢

    //構(gòu)建查詢條件(非必須)
    BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery();
    boolQueryBuilder.must(QueryBuilders.matchQuery("rate_object","item"));
    RangeQueryBuilder publishDateBuilder = QueryBuilders.rangeQuery("created_at");

    publishDateBuilder.from("2018-04-22 00:00:00");//格式需要同你創(chuàng)建索引時的格式匹配
    boolQueryBuilder.filter(publishDateBuilder);

    TransportClient client = factory.getClient();
    SearchResponse response = client.prepareSearch("index")//對應(yīng)索引
                .setTypes("type")//對應(yīng)索引type
                .setQuery(boolQueryBuilder)
                .setScroll(TimeValue.timeValueMinutes(10))//設(shè)置查詢context的存活時間
                .setSize(100)
                .execute()
                .actionGet();

迭代查詢

while (response.getHits().getHits().length>0) {
            String scrollId = response.getScrollId();
            response = client.prepareSearchScroll(scrollId)
                    .setScroll(TimeValue.timeValueMinutes(10))//設(shè)置查詢context的存活時間
                    .execute()
                    .actionGet();

            SearchHits hits = response.getHits();
            for (SearchHit hit:hits.getHits()) {
                String hitString = hit.getSourceAsString();
                System.out.println(hitString);//此處可進行業(yè)務(wù)邏輯
            }         
        }

clean scroll

ClearScrollRequest request = new ClearScrollRequest();
        request.addScrollId(response.getScrollId());
        client.clearScroll(request);