我有一份教育机构文件,如下所示:
{
name: ...,
addresses: [...],
courses: [ {name: ... , duration: ..., tags[...]} ]
}
标签有一个String数组。
我正在尝试找到一个内部有一些标签的课程,例如: java , eclipse , struts 等...... < / p>
我的搜索方法如下:
public BasicDBList coordinates(List tags){
BasicDBObject cmdBody = new BasicDBObject("aggregate", "EducationalInstitution");
List<BasicDBObject> pipeline = new ArrayList<BasicDBObject>();
BasicDBObject projectParams = new BasicDBObject();
projectParams.put("name", 1);
projectParams.put("addresses.state", 1);
projectParams.put("addresses.locs", 1);
projectParams.put("courses", 1);
pipeline.add(new BasicDBObject("$project", projectParams));
pipeline.add(new BasicDBObject("$match", new BasicDBObject("courses.tags", new BasicDBObject("$all", tags))));
pipeline.add(new BasicDBObject("$unwind", "$addresses"));
cmdBody.put("pipeline", pipeline);
if( !getDatastore().getDB().command(cmdBody).ok() ){
throw new MongoException(getDatastore().getDB().command(cmdBody).getErrorMessage());
}
return (BasicDBList) getDatastore().getDB().command(cmdBody).get("result");
}
BasicDBObject cmdBody = new BasicDBObject("aggregate", "EducationalInstitution");
List<BasicDBObject> pipeline = new ArrayList<BasicDBObject>();
BasicDBObject projectParams = new BasicDBObject();
projectParams.put("name", 1);
projectParams.put("addresses.state", 1);
projectParams.put("addresses.locs", 1);
projectParams.put("courses", 1);
pipeline.add(new BasicDBObject("$project", projectParams));
pipeline.add(new BasicDBObject("$match", new BasicDBObject("courses.tags", new BasicDBObject("$all", tags))));
pipeline.add(new BasicDBObject("$unwind", "$addresses"));
cmdBody.put("pipeline", pipeline);
if( !getDatastore().getDB().command(cmdBody).ok() ){
throw new MongoException(getDatastore().getDB().command(cmdBody).getErrorMessage());
}
return (BasicDBList) getDatastore().getDB().command(cmdBody).get("result");
}
这个实现有2个问题:
1-如果一门课程符合某些参数,此查询将返回所有院校课程。例如,如果我搜索 java 并且该机构有一些Java课程,则所有课程都将返回
2-似乎 $ all 效果不佳。 看起来我的查询正在搜索一些教育机构,在其课程中有这些标签,而不是某些课程里面有那些标签
有人可以告诉我我做错了什么吗?
答案 0 :(得分:1)
你必须首先解开课程,否则它将被视为一个数组,查询将尝试找到整个文件(机构)而不是列表元素(课程)
pipeline.add(new BasicDBObject("$project", projectParams));
pipeline.add(new BasicDBObject("$unwind", "$courses"));
pipeline.add(new BasicDBObject("$match", new BasicDBObject("courses.tags", new BasicDBObject("$all", tags))));
pipeline.add(new BasicDBObject("$unwind", "$addresses"));