Elasticsearch之Nested Sorting，elasticsearch
（这是一个小系列：请戳：Elasticsearch之Nested(嵌套)系列，查看其他nested相关文章）
It is possible to sort by the value of a nested field, even though the value exists in a separate nested document. To make the result
more interesting, we will add another record:
尽管存在于独立的nested文本内，基于nested字段的值排序还是可行的。为了让结果更有意思，让我们增加其他的记录：
curl -XPUT 'localhost:9200/my_index/blog/2' -d '
{
"title": "Investment secrets",
"body": "What they don't tell you ...",
"tags": [ "shares", "equities" ],
"comments": [
{
"name": "Mary Brown",
"comment": "Lies, lies, lies",
"age": 42,
"stars": 1,
"date": "2014-10-18"
},
{
"name": "John Smith",
"comment": "You're making it up!",
"age": 28,
"stars": 2,
"date": "2014-10-16"
}
]
}
Imagine that we want to retrieve blog posts that received comments in October, ordered by the lowest number of stars that each blog
post received. The search request would look like this:
设想我们想要检索在10月份被评论的博客文章，同时按每篇文章收到的最低星级排序。检索请求应该类似如下：
curl -XPUT 'localhost:9200/_search' -d '
{
"query":{
"nested":{
"path":"comments",
"filter":{
"range":{
"comments.date":{
"gte":"2014-10-01",
"lt":"2014-11-01"
}
}
}
}
},
"sort":{
"comments.stars":{
"order":"asc",
"mode": "min",
"nested_filter":{
"range":{
"comments.date":{
"gte":"2014-10-01",
"lt":"2014-11-01"
}
}
}
}
}
}Why do we need to repeat the query conditions in the nested_filter? The reason is that sorting happens after the query has been executed.
The query matches blog posts that received comments in October, but it returns blog post documents as the result. If we didn’t include the
nested_filter clause, we would end up sorting based on any comments that the blog post has ever received, not just those received in October.
为什么我们要在nested_filter内重复查询条件？原因是排序发生在查询执行结束后。查询匹配10月收到评论的博客文章，但是它返回博客文章
文本作为结果。如果我们不包括nested_filter语块，那么最终会基于返回的博客文章的所有评论进行排序，而不是在10月份收到的评分。
（！！！根据自己有限的elasticsearch使用经验，这点非常值得各位读者重视！！！）
原文：http://www.elastic.co/guide/en/elasticsearch/guide/current/nested-sorting.html