ElasticSearch-返回唯一值

Question

如何从记录中获取所有语言的值并使它们唯一。

记录

PUT items/1
{ "language" : 10 }

PUT items/2
{ "language" : 11 }

PUT items/3
{ "language" : 10 }

查询

GET items/_search
{ ... }

# => Expected Response
[10, 11]

任何帮助都会很好。

Answer 1

如果您想获取每个语言字段唯一值的第一个文档，您可以这样做：

{
 "query": {
    "match_all": {
    }
  },
  "collapse": {
    "field": "language.keyword",
    "inner_hits": {
    "name": "latest",
      "size": 1
    }
  }
}

Answer 2

我也在为自己寻找这种解决方案。我在术语聚合中找到了引用。

因此，根据下面的说明，是正确的解决方案。

{
"aggs" : {
    "langs" : {
        "terms" : { "field" : "language",  
                    "size" : 500 }
    }
}}

但如果您遇到以下错误：

"error": {
        "root_cause": [
            {
                "type": "illegal_argument_exception",
                "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [fastest_method] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."
            }
        ]}

在这种情况下，您必须在请求中添加“关键字”，如下所示：

   {
    "aggs" : {
        "langs" : {
            "terms" : { "field" : "language.keyword",  
                        "size" : 500 }
        }
    }}

Answer 3

您可以使用术语聚合。

{
"size": 0,
"aggs" : {
    "langs" : {
        "terms" : { "field" : "language",  "size" : 500 }
    }
}}

聚合中的size参数指定聚合结果中包含的最大项数。如果需要所有结果，请将此值设置为大于数据中唯一项的数量。

搜索将返回类似以下内容：

{
"took" : 16,
"timed_out" : false,
"_shards" : {
  "total" : 2,
  "successful" : 2,
  "failed" : 0
},
"hits" : {
"total" : 1000000,
"max_score" : 0.0,
"hits" : [ ]
},
"aggregations" : {
  "langs" : {
    "buckets" : [ {
      "key" : "10",
      "doc_count" : 244812
    }, {
      "key" : "11",
      "doc_count" : 136794
 
    }, {
      "key" : "12",
      "doc_count" : 32312
       } ]
    }
  }
}