google app引擎数据存储区使用“ in”运算符进行查询

问题描述：

Using Query in App Engine Datastore, how do I specify to fetch keys that match a property with variable values?

var Person struct {
   name string
   department string  
}

//Query
q := datastore.NewQuery("Person").Filter("department = ", "department1").KeysOnly()

In the above query, instead of "=" operator, I want "IN" operator to specify more than 1 department value i.e fetch all person keys who belong to department1, department2, department3 etc.

Is this possible with 1 Query? Or do I need to make 1 query for each department?

在App Engine数据存储区中使用查询，如何指定获取与具有可变值的属性匹配的键？ p>

  var Person结构{
名称字符串
部门字符串
} 
 
 // Query 
q：= datastore.NewQuery（“ Person”）。Filter（“  department =“，” department1“）。KeysOnly（）
  code>  pre> 
 
 在上面的查询中，我要使用” =“  strong>运算符 “ IN”运算符可指定多个1部门值，即获取属于部门1，部门2，部门3等的所有人员密钥。 p> 
 
 
使用1个查询是否可行？ 还是我需要为每个部门查询1个？ p> 
  div>

答

Other runtimes allow "IN" operator for datastore queries. It is, however, just a convenience: under the hood, the datastore makes individual queries for each element in the list.

If you have a relatively small number of entities, it may be more efficient to retrieve all of them and then filter the results based on the "department" property, rather than issues N queries to search for N possible departments.

google app引擎数据存储区使用“ in”运算符进行查询

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