ElasticSearch使用搜索功能

• 简单的搜索

一个 GET 是相当简单的，可以直接得到指定的文档。现在尝试点儿稍微高级的功能，比如一个简单的搜索！

第一个尝试的几乎是最简单的搜索了。我们使用下列请求来搜索所有雇员：

可以看到，我们仍然使用索引库 megacorp 以及类型 employee，但与指定一个文档 ID 不同，这次使用 _search 。返回结果包括了所有三个文档，放在数组 hits 中。一个搜索默认返回十条结果。

{
    "took": 9,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "failed": 0
    },
    "hits": {
        "total": 3,
        "max_score": 1.0,
        "hits": [
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "2",
                "_score": 1.0,
                "_source": {
                    "first_name": "Jane",
                    "last_name": "Smith",
                    "age": 32,
                    "about": "I like to collect rock albums",
                    "interests": [
                        "music"
                    ]
                }
            },
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "1",
                "_score": 1.0,
                "_source": {
                    "first_name": "John",
                    "last_name": "Smith",
                    "age": 26,
                    "about": "I love to go rock climbing",
                    "interests": [
                        "sports",
                        "music"
                    ]
                }
            },
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "3",
                "_score": 1.0,
                "_source": {
                    "first_name": "Douglas",
                    "last_name": "Fir",
                    "age": 35,
                    "about": "I like to build cabinets",
                    "interests": [
                        "forestry"
                    ]
                }
            }
        ]
    }
}

注意：返回结果不仅告知匹配了哪些文档，还包含了整个文档本身：显示搜索结果给最终用户所需的全部信息。

接下来，尝试下搜索姓氏为 Smith 的雇员。为此，我们将使用一个 高亮 搜索，很容易通过命令行完成。这个方法一般涉及到一个 查询字符串 （query-string） 搜索，因为我们通过一个URL参数来传递查询信息给搜索接口：

GET /megacorp/employee/_search?q=last_name:Smith

返回结果

{
    "took": 7,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 0.30685282,
        "hits": [
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "2",
                "_score": 0.30685282,
                "_source": {
                    "first_name": "Jane",
                    "last_name": "Smith",
                    "age": 32,
                    "about": "I like to collect rock albums",
                    "interests": [
                        "music"
                    ]
                }
            },
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "1",
                "_score": 0.30685282,
                "_source": {
                    "first_name": "John",
                    "last_name": "Smith",
                    "age": 26,
                    "about": "I love to go rock climbing",
                    "interests": [
                        "sports",
                        "music"
                    ]
                }
            }
        ]
    }
}

• 利用DSL搜索

Query-string 搜索通过命令非常方便地进行临时性的即席搜索 ，但它有自身的局限性（参见 轻量 搜索 ）。Elasticsearch提供一个丰富灵活的查询语言叫做 查询表达式 ， 它支持构建更加复杂和健壮的查询。

领域特定语言 （DSL）， 使用 JSON构造了一个请求。我们可以像这样重写之前的查询所有名为 Smith 的搜索 ：

GET /megacorp/employee/_search

{
    "query" : {
        "match" : {
            "last_name" : "Smith"
        }
    }
}

返回结果

{
    "took": 18,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 0.30685282,
        "hits": [
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "2",
                "_score": 0.30685282,
                "_source": {
                    "first_name": "Jane",
                    "last_name": "Smith",
                    "age": 32,
                    "about": "I like to collect rock albums",
                    "interests": [
                        "music"
                    ]
                }
            },
            {
                "_index": "megacorp",
                "_type": "employee",
                "_id": "1",
                "_score": 0.30685282,
                "_source": {
                    "first_name": "John",
                    "last_name": "Smith",
                    "age": 26,
                    "about": "I love to go rock climbing",
                    "interests": [
                        "sports",
                        "music"
                    ]
                }
            }
        ]
    }
}

好了，这节课讲了几本搜索功能和如何利用DSL搜索，下一节课讲一下如何排序？