Elasticsearch Function Score Query 分数差异

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最近接手搜索引擎后，精简调优代码后，测试同学发现个问题，就是最终_score的计算和最初不同了，多了2分。

经过explain后，查看发现的新增的两个字段造成的分值变化，默认的boost是1，两个自然是多了2。

那么这个分是怎么来的呢？经过调试发现，我增加的筛选是类似如下的方式：

$this->query['function_score']['query']['bool']['must'][] = [
	'term' => [ 'hdsd' => 1 ]
];

而类比之前的代码，改为

$this->query['function_score']['query']['bool']['filter'][] = [
	'term' => [ 'hdsd' => 1 ]
];

之后，就不会累加默认的boost分数了。分数至此，恢复了最初的状态。

翻阅了下官方的文档，找到了说明，至此问题明了了。

表格说明摘录如下：

Occur	Description
`must`	The clause (query) must appear in matching documents and will contribute to the score.
`filter`	The clause (query) must appear in matching documents. However unlike `must` the score of the query will be ignored. Filter clauses are executed in filter context, meaning that scoring is ignored and clauses are considered for caching.
`should`	The clause (query) should appear in the matching document. If the `bool` query is in a query context and has a `must` or `filter` clause then a document will match the `bool` query even if none of the `should` queries match. In this case these clauses are only used to influence the score. If the `bool` query is a filter context or has neither `must` or `filter` then at least one of the `should` queries must match a document for it to match the `bool` query. This behavior may be explicitly controlled by setting the `minimum_should_match` parameter.
`must_not`	The clause (query) must not appear in the matching documents. Clauses are executed in filter context meaning that scoring is ignored and clauses are considered for caching. Because scoring is ignored, a score of `0` for all documents is returned.

以上文档整理自： Bool Query

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