elasticsearch function_score Query——文档排序结果的最后一道墙
function_score Query Thefunction_scorequeryis the ultimate tool for taking control of the scoring process.It allows you to apply a function to each document that matches the main query in order to alter or completely replace the original query_score. In fact, you can apply different functions tosubsetsof the main result set by using filters, which gives you the best of both worlds: efficient scoring with cacheable filters. It supports several predefined functions out of the box: weight Apply a simple boost to each document without the boost being normalized: a weightof 2results in 2 * _score. field_value_factor Use the value of a field in the document to alter the _score, such as factoring in a popularitycount or number of votes. random_score Use consistently random scoring to sort results differently for every user, while maintaining the same sort order for a single user. Decay functions—linear,exp,gauss Incorporate sliding-scale values like publish_date, geo_location, or priceinto the _scoreto prefer recently published documents, documents near a latitude/longitude (lat/lon) point, or documents near a specified price point. script_score Use a custom script to take complete control of the scoring logic. If your needs extend beyond those of the functions in this list, write a custom script to implement the logic that you need. Without thefunction_scorequery, we would not be able to combine the score from a full-text query with a factor like recency. We would have to sort either by_scoreor bydate; the effect of one would obliterate the effect of the other. This query allows you to blend the two together: to still sort by full-text relevance, but giving extra weight to recently published documents, or popular documents, or products that are near the user’s price point. As you can imagine, a query that supports all of this can look fairly complex. We’ll start with a simple use case and work our way up the complexity ladder. 转自：https://www.elastic.co/guide/en/elasticsearch/guide/current/function-score-query.html 本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/bonelee/p/6480761.html，如需转载请自行联系原作者
