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目前这个功能还是处于试验阶段。在未来的版本中可能会出现变化。基于 Vector（向量）的打分目前分为一下两种：
- Dense_vector
- Spare_vector
它们都是基于功能进行评分的。在实际的使用中，我们必须注意的是：向量函数的计算过程中，所有匹配的文档均被线性扫描。 因此，期望查询时间随匹配文档的数量线性增长。 因此，我们建议使用查询参数限制匹配文档的数量。
准备数据
我们首先创建一个叫做 books 的索引，并定义它的 mapping 如下：
代码语言：javascript复制PUT books{ "mappings": { "properties": { "author": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "category": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "format": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "isbn13": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "pages": { "type": "long" }, "price": { "type": "float" }, "publisher": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "rating": { "type": "float" }, "release_year": { "type": "date", "format": "strict_year" }, "title": { "type": "text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } }, "vector_recommendation": { "type": "dense_vector", "dims": 3 } } }}然后，我们使用 bulk API 接口来导入数据：
代码语言：javascript复制PUT books/_bulk{ "index" : { "_id" : "database-internals" } }{"isbn13":"978-1492040347","author":"Alexander Petrov", "title":"Database Internals: A deep-dive into how distributed data systems work","publisher":"O'Reilly","category":["databases","information systems"],"pages":350,"price":47.28,"format":"paperback","rating":4.5, "release_year" : "2019", "vector_recommendation" : [3.5, 4.5, 5.2]}{ "index" : { "_id" : "designing-data-intensive-applications" } }{"isbn13":"978-1449373320", "author":"Martin Kleppmann", "title":"Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems","publisher":"O'Reilly","category":["databases" ],"pages":590,"price":31.06,"format":"paperback","rating":4.4, "release_year" : "2017", "vector_recommendation" : [5.9, 4.4, 6.8]}{ "index" : { "_id" : "kafka-the-definitive-guide" } }{"isbn13":"978-1491936160","author":[ "Neha Narkhede", "Gwen Shapira", "Todd Palino"], "title":"Kafka: The Definitive Guide: Real-time data and stream processing at scale", "publisher":"O'Reilly","category":["databases" ],"pages":297,"price":37.31,"format":"paperback","rating":3.9, "release_year" : "2017", "vector_recommendation" : [2.97, 3.9, 6.2]}{ "index" : { "_id" : "effective-java" } }{"isbn13":"978-1491936160","author": "Joshua Block", "title":"Effective Java", "publisher":"Addison-Wesley", "category":["programming languages", "java" ],"pages":412,"price":27.91,"format":"paperback","rating":4.2, "release_year" : "2017", "vector_recommendation" : [4.12, 4.2, 7.2]}{ "index" : { "_id" : "daemon" } }{"isbn13":"978-1847249616","author":"Daniel Suarez", "title":"Daemon","publisher":"Quercus","category":["dystopia","novel"],"pages":448,"price":12.03,"format":"paperback","rating":4.0, "release_year" : "2011", "vector_recommendation" : [4.48, 4.0, 8.7]}{ "index" : { "_id" : "cryptonomicon" } }{"isbn13":"978-1847249616","author":"Neal Stephenson", "title":"Cryptonomicon","publisher":"Avon","category":["thriller", "novel" ],"pages":1152,"price":6.99,"format":"paperback","rating":4.0, "release_year" : "2002", "vector_recommendation" : [10.0, 4.0, 9.3]}{ "index" : { "_id" : "garbage-collection-handbook" } }{"isbn13":"978-1420082791","author": [ "Richard Jones", "Antony Hosking", "Eliot Moss" ], "title":"The Garbage Collection Handbook: The Art of Automatic Memory Management","publisher":"Taylor & Francis","category":["programming algorithms" ],"pages":511,"price":87.85,"format":"paperback","rating":5.0, "release_year" : "2011", "vector_recommendation" : [5.1, 5.0, 1.3] }{ "index" : { "_id" : "radical-candor" } }{"isbn13":"978-1250258403","author": "Kim Scott", "title":"Radical Candor: Be a Kick-Ass Boss Without Losing Your Humanity","publisher":"Macmillan","category":["human resources","management", "new work"],"pages":404,"price":7.29,"format":"paperback","rating":4.0, "release_year" : "2018", "vector_recommendation" : [4.0, 4.0, 9.2] }这样我们的索引 books 中有8个文档。我们仔细地查看一下我们输入的数据，它里面含有一个叫做 vecto_recommendation 的字段
代码语言：javascript复制"vector_recommendation" : [3.5, 4.5, 5.2]- 向量里的第一个数据3.5，实际上是我们的在这个文档里的 pages 除以100而得到的。如果这本书的页数越多，则表示这个数值越大。它的范围在0-10之间
- 向量里的第二个数据是这本书的 rating，也即评价。这个值在这个文档里的 rating 项可以查到。范围在0-5之间
- 向量里的第三个数据是书的价钱，这个值越低表明，价钱越贵，因为我们都喜欢便宜一点的书籍。0代表100元以上，10则表示10元以下的书
在上面的 mapping 中，我们是这样定义的：
代码语言：javascript复制 "vector_recommendation": { "type": "dense_vector", "dims": 3 }它定义了这个 vector_recommendation 的类型是 dense_vector，它是一个3维的向量。
现在我们的数据都已经准备好了。我们接下来做一些我们喜欢的搜索。
搜索短的，便宜的并且评价高的书
在上面我们已经建立了我们的向量模型。那么我们怎么能够找到那些书的页数比较少，便宜的而且评价非常高的书呢？我们可以采用如下的搜索方式：
代码语言：javascript复制GET books/_search{ "query": { "script_score": { "query": { "match_all": {} }, "script": { "source": "cosineSimilarity(params.query_vector, doc['vector_recommendation']) 1.0", "params": { "query_vector": [ 1, 5, 10 ] } } } }}在这里，我们使用 script_score。如果你对这个不是很了解的话，可以参阅我之前的文章 “Elasticsearch：使用function_score及soft_score定制搜索结果的分数”来做更进一步的了解。
在上面的搜索中，我们通过脚本：
代码语言：javascript复制cosineSimilarity(params.query_vector, doc['vector_recommendation']) 1.0来计算我们的搜索的分数。这里加上1的作用是为了避免我们最后的分数是负数。
在上面的表达式中：
代码语言：javascript复制 "params": { "query_vector": [ 1, 5, 10 ] }我们想寻找的书是最好是100页的书，因为第一项是1；我们也同时想找一个评价好的书，因为第二项是5；同时我们想找最便宜的书，因为第三项是10。按照上面的要求，我们可以得到如下的搜索结果：
代码语言：javascript复制/*
* 提示：该行代码过长，系统自动注释不进行高亮。一键复制会移除系统注释
* "hits" : [ { "_index" : "books", "_type" : "_doc", "_id" : "radical-candor", "_score" : 1.9568613, "_source" : { "isbn13" : "978-1250258403", "author" : "Kim Scott", "title" : "Radical Candor: Be a Kick-Ass Boss Without Losing Your Humanity", "publisher" : "Macmillan", "category" : [ "human resources", "management", "new work" ], "pages" : 404, "price" : 7.29, "format" : "paperback", "rating" : 4.0, "release_year" : "2018", "vector_recommendation" : [ 4.0, 4.0, 9.2 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "kafka-the-definitive-guide", "_score" : 1.9520907, "_source" : { "isbn13" : "978-1491936160", "author" : [ "Neha Narkhede", "Gwen Shapira", "Todd Palino" ], "title" : "Kafka: The Definitive Guide: Real-time data and stream processing at scale", "publisher" : "O'Reilly", "category" : [ "databases" ], "pages" : 297, "price" : 37.31, "format" : "paperback", "rating" : 3.9, "release_year" : "2017", "vector_recommendation" : [ 2.97, 3.9, 6.2 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "daemon", "_score" : 1.9394372, "_source" : { "isbn13" : "978-1847249616", "author" : "Daniel Suarez", "title" : "Daemon", "publisher" : "Quercus", "category" : [ "dystopia", "novel" ], "pages" : 448, "price" : 12.03, "format" : "paperback", "rating" : 4.0, "release_year" : "2011", "vector_recommendation" : [ 4.48, 4.0, 8.7 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "effective-java", "_score" : 1.9305289, "_source" : { "isbn13" : "978-1491936160", "author" : "Joshua Block", "title" : "Effective Java", "publisher" : "Addison-Wesley", "category" : [ "programming languages", "java" ], "pages" : 412, "price" : 27.91, "format" : "paperback", "rating" : 4.2, "release_year" : "2017", "vector_recommendation" : [ 4.12, 4.2, 7.2 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "database-internals", "_score" : 1.9005439, "_source" : { "isbn13" : "978-1492040347", "author" : "Alexander Petrov", "title" : "Database Internals: A deep-dive into how distributed data systems work", "publisher" : "O'Reilly", "category" : [ "databases", "information systems" ], "pages" : 350, "price" : 47.28, "format" : "paperback", "rating" : 4.5, "release_year" : "2019", "vector_recommendation" : [ 3.5, 4.5, 5.2 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "designing-data-intensive-applications", "_score" : 1.8525991, "_source" : { "isbn13" : "978-1449373320", "author" : "Martin Kleppmann", "title" : "Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems", "publisher" : "O'Reilly", "category" : [ "databases" ], "pages" : 590, "price" : 31.06, "format" : "paperback", "rating" : 4.4, "release_year" : "2017", "vector_recommendation" : [ 5.9, 4.4, 6.8 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "cryptonomicon", "_score" : 1.7700485, "_source" : { "isbn13" : "978-1847249616", "author" : "Neal Stephenson", "title" : "Cryptonomicon", "publisher" : "Avon", "category" : [ "thriller", "novel" ], "pages" : 1152, "price" : 6.99, "format" : "paperback", "rating" : 4.0, "release_year" : "2002", "vector_recommendation" : [ 10.0, 4.0, 9.3 ] } }, { "_index" : "books", "_type" : "_doc", "_id" : "garbage-collection-handbook", "_score" : 1.528916, "_source" : { "isbn13" : "978-1420082791", "author" : [ "Richard Jones", "Antony Hosking", "Eliot Moss" ], "title" : "The Garbage Collection Handbook: The Art of Automatic Memory Management", "publisher" : "Taylor & Francis", "category" : [ "programming algorithms" ], "pages" : 511, "price" : 87.85, "format" : "paperback", "rating" : 5.0, "release_year" : "2011", "vector_recommendation" : [ 5.1, 5.0, 1.3 ] } } ]
*/我们可以看出来 “Radical Candor: Be a Kick-Ass Boss Without Losing Your Humanity” 是最贴近的书。我们可以看一下它的recommendation_vector:
代码语言：javascript复制 "vector_recommendation" : [ 4.0, 4.0, 9.2 ]这是所有的书里最贴近我们搜索要求的书了。
参考：
【1】https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-script-score-query.html#vector-functions
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