# 索引->别名/是否存在/类型存在

## 索引->别名/是否存在/是否类型存在

## Indices Exists /索引是否存在

用来检查如果 index ( indics )是否存在。例如:

```
curl -XHEAD 'localhost:9200/twitter?pretty'
```

HTTP状态码表示index存在与否。404意味着它不存在，200即存在。

## Types Exists/类型是否存在

用于检查是否一个类型存在于索引。

```
HEAD twitter/_mapping/tweet
```

HTTP状态码表示type存在与否。404意味着它不存在，200即存在。

## Index Aliases /索引别名

这是一个示例将别名`alias1`指定索引`test1`:

```
POST /_aliases
{
    "actions" : [
        { "add" : { "index" : "test1", "alias" : "alias1" } }
    ]
}
```

这是删除相同的别名:

```
POST /_aliases
{
    "actions" : [
        { "remove" : { "index" : "test1", "alias" : "alias1" } }
    ]
}
```

重命名一个别名是一个简单的删除然后添加操作在同一个API。这个操作是原子的,不需要担心短时间内的别名不指向索引:

```
POST /_aliases
{
    "actions" : [
        { "remove" : { "index" : "test1", "alias" : "alias1" } },
        { "add" : { "index" : "test2", "alias" : "alias1" } }
    ]
}
```

将别名指向一个以上的索引只是几个添加操作:

```
POST /_aliases
{
    "actions" : [
        { "add" : { "index" : "test1", "alias" : "alias1" } },
        { "add" : { "index" : "test2", "alias" : "alias1" } }
    ]
}
```

可以指定多个索引的操作,采用索引数组的语法:

```
POST /_aliases
{
    "actions" : [
        { "add" : { "indices" : ["test1", "test2"], "alias" : "alias1" } }
    ]
}
```

在一个动作指定多个别名,相应的别名数组语法也存在。

在上面的示例中,正则匹配模式还可以用于别名关联到多个索引共享一个共同的名字:

```
POST /_aliases
{
    "actions" : [
        { "add" : { "index" : "test*", "alias" : "all_test_indices" } }
    ]
}
```

更多复杂操作请看官方文档:[Index Aliases](https://www.elastic.co/guide/en/elasticsearch/reference/5.2/indices-aliases.html)


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