Question

我在mongodb java驱动程序中使用地理空间查询，使用以下代码获取给定位置周围的位置：

BasicDBObject myCmd = new BasicDBObject(); 

myCmd.append("geoNear", collectionName); 
double[] loc = {5,5}; 
myCmd.append("near", loc); 
myCmd.append("spherical", true); 
myCmd.append("distanceMultiplier", 6378000);
myCmd.append("maxDistance", 200); 

BasicDBList results = (BasicDBList)myResults.get("results");
for( Iterator< Object > it = results.iterator(); it.hasNext(); )
{
    BasicDBObject result  = (BasicDBObject) it.next();
    BasicDBObject dbo = (BasicDBObject) result.get("obj");
    System.out.println(dbo.getString("name"));
}

到目前为止，此工作正常。我遇到麻烦的地方是增加额外的选择标准。即我的集合有一个名为category的字段，我想将该类别添加到查询中。例如给我属于给定类别的所有位置。

期待收到您的答案和提示！

BR 马丁

Answer 1

根据geoNear docs限制地理空间查询某些其他属性，您可以将文档添加为查询参数。

BasicDBObject myCmd = new BasicDBObject(); 
BasicDBObject myQuery = new BasicDBObject();    

myCmd.append("geoNear", collectionName); 
double[] loc = {5,5}; 
myCmd.append("near", loc); 
myCmd.append("spherical", true); 
myCmd.append("distanceMultiplier", 6378000);
myCmd.append("maxDistance", 200); 

//construct a query document from another BasicDBOject
myQuery.append("category":"some category");
//add this as a query document
myCmd.append("query", myQuery);

BasicDBList results = (BasicDBList)myResults.get("results");
for( Iterator< Object > it = results.iterator(); it.hasNext(); )
{
    BasicDBObject result  = (BasicDBObject) it.next();
    BasicDBObject dbo = (BasicDBObject) result.get("obj");
    System.out.println(dbo.getString("name"));
}

MongoDB Java Geospatial Query where子句

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