ES设置查询的相似度算法
similarity Elasticsearch allows you to configure a scoring algorithm orsimilarityper field. Thesimilaritysetting provides a simple way of choosing a similarity algorithm other than the defaultBM25, such asTF/IDF. Similarities are mostly useful fortextfields, but can also apply to other field types. Custom similarities can be configured by tuning the parameters of the built-in similarities. For more details about this expert options, see thesimilarity module. The only similarities which can be used out of the box, without any further configuration are: BM25 The Okapi BM25 algorithm. The algorithm used by default in Elasticsearch and Lucene. See Pluggable Similarity Algorithmsfor more information. classic The TF/IDF algorithm which used to be the default in Elasticsearch and Lucene. See Lucene’s Practical Scoring Functionfor more information. boolean A simple boolean similarity, which is used when full-text ranking is not needed and the score should only be based on whether the query terms match or not. Boolean similarity gives terms a score equal to their query boost. Thesimilaritycan be set on the field level when a field is first created, as follows: PUT my_index { "mappings": { "my_type": { "properties": { "default_field": { "type": "text" }, "classic_field": { "type": "text", "similarity": "classic" }, "boolean_sim_field": { "type": "text", "similarity": "boolean" } } } } } COPY AS CURL VIEW IN CONSOLE Thedefault_fielduses theBM25similarity. Theclassic_fielduses theclassicsimilarity (ie TF/IDF). Theboolean_sim_fielduses thebooleansimilarity. Default and Base Similarities By default, Elasticsearch will use whatever similarity is configured asdefault. However, the similarity functionsqueryNorm()andcoord()are not per-field. Consequently, for expert users wanting to change the implementation used for these two methods, while not changing thedefault, it is possible to configure a similarity with the namebase. This similarity will then be used for the two methods. You can change the default similarity for all fields in an index when it iscreated: PUT /my_index { "settings": { "index": { "similarity": { "default": { "type": "classic" } } } } } If you want to change the default similarity after creating the index you mustcloseyour index, send the follwing request andopenit again afterwards: PUT /my_index/_settings { "settings": { "index": { "similarity": { "default": { "type": "classic" } } } } } from:https://www.elastic.co/guide/en/elasticsearch/reference/5.4/index-modules-similarity.html 本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/bonelee/p/7451929.html，如需转载请自行联系原作者
