java - Objectify:排序查询结果 ("no matching index found"错误)

Question

我在执行下面查询的浏览器上收到此错误，但没有 ".order("position") 它工作(但结果显然没有排序)。

Uncaught com.google.web.bindery.event.shared.UmbrellaException: Exception caught: Server Error: no matching index found.
The suggested index for this query is:
    <datastore-index kind="Box" ancestor="false" source="manual">
        <property name="diagram_id" direction="asc"/>
        <property name="position" direction="asc"/>
    </datastore-index>

BoxDao.java

public List<Box> listFromDiagram(String diagramId)
{
    Objectify ofy = ObjectifyService.begin();
    // List of boxes of that diagram ordered by position asc
    Query<Box> q=ofy.query(Box.class).filter("diagram_id",diagramId).order("position");
    List<Box> results = q.list();

    return results;
}

Box.java

import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Indexed;

@Entity
public class Box extends DatastoreObject{
    @Indexed private String boxId;
    @Indexed private String diagram_id;
    private String title;
    @Indexed private int position;
[...]
}

文件“datastore-indexes.xml”是空的……有什么想法吗？谢谢

Answer 1

您需要一个多属性索引(您按一个属性过滤并按另一个属性排序)。错误消息告诉您需要在 datastore-indexes.xml 中放入什么。有关概念性概述，请参阅:

https://code.google.com/p/objectify-appengine/wiki/Concepts#Indexes

我建议您也点击 Google 文档的链接。