ElasticSearch--去重查询/根据字段去重--方法/方案

雨点打透心脏的1/2处 2022-09-16 03:51 1737阅读 0赞

原文网址：[ElasticSearch--去重查询/根据字段去重--方法/方案\_IT利刃出鞘的博客-CSDN博客][ElasticSearch--_--_IT_-CSDN]

# 简介 #

本文介绍如何根据某一个字段进行去重。包括：获取去重后的结果，统计去重后的数量。

在SQL中，我们可以用dinstinct语句进行去重，例如：

*  获取去重后的结果：SELECT DISTINCT name, sex FROM person;
 *  统计去重后的数量：SELECT COUNT(DISTINCT name, sex) FROM person;

Elasticsearch也可以做到获取去重后的结果，统计去重后的数量，例如：

*  获取去重后的结果
    
     *  方案1：collapse折叠功能(ES5.3之后支持)
        
         *  **推荐。**原因：性能高，占内存小
     *  方案2：字段聚合+top\_hits聚合
        
         *  **不推荐**。原因：性能差，占内存大
 *  统计去重后的数量
    
     *  聚合+cardinality聚合函数

# 索引结构及数据 #

**索引结构**

http://localhost:9200/  
PUT blog

{
        "mappings": {
            "properties": {
                "id":{
                    "type":"long"
                },
                "title": {
                    "type": "text"
                },
                "content": {
                    "type": "text"
                },
                "author":{
                    "type": "text",
                    "fields": {
                        "keyword": {
                            "type": "keyword"
                        }
                    }
                },
                "category":{
                    "type": "keyword"
                },
                "createTime": {
                    "type": "date",
                    "format":"yyyy-MM-dd HH:mm:ss.SSS||yyyy-MM-dd'T'HH:mm:ss.SSS||yyyy-MM-dd HH:mm:ss||epoch_millis"
                },
                "updateTime": {
                    "type": "date",
                    "format":"yyyy-MM-dd HH:mm:ss.SSS||yyyy-MM-dd'T'HH:mm:ss.SSS||yyyy-MM-dd HH:mm:ss||epoch_millis"
                },
                "status":{
                    "type":"integer"
                },
                "serialNum": {
                    "type": "keyword"
                }
            }
        }
    }

**数据**

*  每个文档必须独占一行，不能换行。
 *  此命令要放到postman中去执行，如果用head执行会失败

http://localhost:9200/  
POST \_bulk

{"index":{"_index":"blog","_id":1}}
    {"blogId":1,"title":"Spring Data ElasticSearch学习教程1","content":"这是批量添加的文档1","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"1","createTime":"2021-10-10 11:52:01.249","updateTime":null}
    {"index":{"_index":"blog","_id":2}}
    {"blogId":2,"title":"Spring Data ElasticSearch学习教程2","content":"这是批量添加的文档2","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"2","createTime":"2021-10-10 11:52:02.249","updateTime":null}
    {"index":{"_index":"blog","_id":3}}
    {"blogId":3,"title":"Spring Data ElasticSearch学习教程3","content":"这是批量添加的文档3","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"3","createTime":"2021-10-10 11:52:03.249","updateTime":null}
    {"index":{"_index":"blog","_id":4}}
    {"blogId":4,"title":"Spring Data ElasticSearch学习教程4","content":"这是批量添加的文档4","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"4","createTime":"2021-10-10 11:52:04.249","updateTime":null}
    {"index":{"_index":"blog","_id":5}}
    {"blogId":5,"title":"Spring Data ElasticSearch学习教程5","content":"这是批量添加的文档5","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"5","createTime":"2021-10-10 11:52:05.249","updateTime":null}
    {"index":{"_index":"blog","_id":6}}
    {"blogId":6,"title":"Java学习教程6","content":"这是批量添加的文档6","author":"Tony","category":"ElasticSearch","status":1,"serialNum":"6","createTime":"2021-10-10 11:52:06.249","updateTime":null}
    {"index":{"_index":"blog","_id":7}}
    {"blogId":7,"title":"Java学习教程7","content":"这是批量添加的文档7","author":"Pepper","category":"ElasticSearch","status":1,"serialNum":"7","createTime":"2021-10-10 11:52:07.249","updateTime":null}
    {"index":{"_index":"blog","_id":8}}
    {"blogId":8,"title":"Java学习教程8","content":"这是批量添加的文档8","author":"Pepper","category":"ElasticSearch","status":1,"serialNum":"8","createTime":"2021-10-10 11:52:08.249","updateTime":null}
    {"index":{"_index":"blog","_id":9}}
    {"blogId":9,"title":"Java学习教程9","content":"这是批量添加的文档9","author":"Pepper","category":"ElasticSearch","status":1,"serialNum":"9","createTime":"2021-10-10 11:52:09.249","updateTime":null}
    {"index":{"_index":"blog","_id":10}}
    {"blogId":10,"title":"Java学习教程10","content":"这是批量添加的文档10","author":"Pepper","category":"ElasticSearch","status":1,"serialNum":"10","createTime":"2021-10-10 11:52:10.249","updateTime":null}

执行之后的结果

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16][]

# 实例：手写DSL #

去重的字段不能是text类型。所以，author的mapping要有keyword，且通过author.keyword去重。

如果去重字段是其他可以直接去重的类型，比如：数字类型、keyword、日期等，则直接用字段名就可以。即：如果本处author是keyword，则author.keyword处写成author就行。

## collapse获取去重结果 ##

POST /blog/\_search

{
        "query": {
            "match": {
                "title":{
                    "query": "java"
                }
            }
        },
        "collapse":{
            "field": "author.keyword"
        }
    }

结果：

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 1][]

我把结果全部贴出来

{
        "took": 2,
        "timed_out": false,
        "_shards": {
            "total": 5,
            "successful": 5,
            "skipped": 0,
            "failed": 0
        },
        "hits": {
            "total": {
                "value": 5,
                "relation": "eq"
            },
            "max_score": null,
            "hits": [{
                    "_index": "blog",
                    "_type": "_doc",
                    "_id": "9",
                    "_score": 1.0596458,
                    "_source": {
                        "blogId": 9,
                        "title": "Java学习教程9",
                        "content": "这是批量添加的文档9",
                        "author": "Pepper",
                        "category": "ElasticSearch",
                        "status": 1,
                        "serialNum": "9",
                        "createTime": "2021-10-10 11:52:09.249",
                        "updateTime": null
                    },
                    "fields": {
                        "author.keyword": [
                            "Pepper"
                        ]
                    }
                }, {
                    "_index": "blog",
                    "_type": "_doc",
                    "_id": "6",
                    "_score": 0.7361701,
                    "_source": {
                        "blogId": 6,
                        "title": "Java学习教程6",
                        "content": "这是批量添加的文档6",
                        "author": "Tony",
                        "category": "ElasticSearch",
                        "status": 1,
                        "serialNum": "6",
                        "createTime": "2021-10-10 11:52:06.249",
                        "updateTime": null
                    },
                    "fields": {
                        "author.keyword": [
                            "Tony"
                        ]
                    }
                }
            ]
        }
    }

## 聚合获取去重结果 ##

POST /blog/\_search

{
        "query": {
            "match": {
                "title": {
                    "query": "java"
                }
            }
        },
        "size": 0,
        "aggs": {
            "author_aggs": {
                "terms": {
                    "field": "author.keyword",
                    "size": 10
                },
                "aggs": {
                    "author_top": {
                        "top_hits": {
                            "sort": [{
                                    "author.keyword": {
                                        "order": "desc"
                                    }
                                }
                            ],
                            "size": 1
                        }
                    }
                }
            }
        }
    }

结果

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 2][]

我把结果全部贴出来

{
        "took": 2,
        "timed_out": false,
        "_shards": {
            "total": 5,
            "successful": 5,
            "skipped": 0,
            "failed": 0
        },
        "hits": {
            "total": {
                "value": 5,
                "relation": "eq"
            },
            "max_score": null,
            "hits": []
        },
        "aggregations": {
            "author_aggs": {
                "doc_count_error_upper_bound": 0,
                "sum_other_doc_count": 0,
                "buckets": [{
                        "key": "Pepper",
                        "doc_count": 4,
                        "author_top": {
                            "hits": {
                                "total": {
                                    "value": 4,
                                    "relation": "eq"
                                },
                                "max_score": null,
                                "hits": [{
                                        "_index": "blog",
                                        "_type": "_doc",
                                        "_id": "9",
                                        "_score": null,
                                        "_source": {
                                            "blogId": 9,
                                            "title": "Java学习教程9",
                                            "content": "这是批量添加的文档9",
                                            "author": "Pepper",
                                            "category": "ElasticSearch",
                                            "status": 1,
                                            "serialNum": "9",
                                            "createTime": "2021-10-10 11:52:09.249",
                                            "updateTime": null
                                        },
                                        "sort": [
                                            "Pepper"
                                        ]
                                    }
                                ]
                            }
                        }
                    }, {
                        "key": "Tony",
                        "doc_count": 1,
                        "author_top": {
                            "hits": {
                                "total": {
                                    "value": 1,
                                    "relation": "eq"
                                },
                                "max_score": null,
                                "hits": [{
                                        "_index": "blog",
                                        "_type": "_doc",
                                        "_id": "6",
                                        "_score": null,
                                        "_source": {
                                            "blogId": 6,
                                            "title": "Java学习教程6",
                                            "content": "这是批量添加的文档6",
                                            "author": "Tony",
                                            "category": "ElasticSearch",
                                            "status": 1,
                                            "serialNum": "6",
                                            "createTime": "2021-10-10 11:52:06.249",
                                            "updateTime": null
                                        },
                                        "sort": [
                                            "Tony"
                                        ]
                                    }
                                ]
                            }
                        }
                    }
                ]
            }
        }
    }

## 聚合获取去重数量 ##

POST /blog/\_search

{
        "query": {
            "match": {
                "title": {
                    "query": "java"
                }
            }
        },
        "size": 0,
        "aggs": {
            "author_aggs": {
                "cardinality": {
                    "field": "author.keyword"
                }
            }
        }
    }

结果

# ![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 3][]实例：Java代码 #

## collapse获取去重结果 ##

见：[Spring Data Elasticsearch--ElasticsearchRestTemplate--使用/用法/教程/实例\_IT利刃出鞘的博客-CSDN博客][Spring Data Elasticsearch--ElasticsearchRestTemplate--_IT_-CSDN]

在这个网址里搜索“去重”

# 其他网址 #

[Elasticsearch去重查询\_jacklife的博客-CSDN博客\_es去重查询][Elasticsearch_jacklife_-CSDN_es]

[ElasticSearch--_--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/120773450
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/86b981737cdd4de5aabdb43f327965ef.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220828/8c7f0be1adba49a98fa5a540a3ef7a78.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 2]: /images/20220828/afdd0682c5d44511a1c680c332c8fc9d.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16 3]: /images/20220828/1ed151e577f84f8ea2005006da317f5b.png
[Spring Data Elasticsearch--ElasticsearchRestTemplate--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/120706299
[Elasticsearch_jacklife_-CSDN_es]: https://blog.csdn.net/wslyk606/article/details/84315862