Question

从MongoDB Java驱动程序版本2.10.1设置分片键的语法是什么？

或者换句话说，我如何使用Java驱动程序执行此操作？

sh.shardCollection("test.a", {"_id": "hashed"}})

Answer 1

简短回答：您应该发出shardCollection命令。

答案很长：

MongoDB shell中的sh.shardCollection只是在admin db上调用命令的辅助方法。

如果在MongoDB shell中输入sh.shardCollection，您将看到此函数实际执行的操作：

> sh.shardCollection
function ( fullName , key , unique ) {
    sh._checkFullName( fullName )
    assert( key , "need a key" )
    assert( typeof( key ) == "object" , "key needs to be an object" )

    var cmd = { shardCollection : fullName , key : key }
    if ( unique )
        cmd.unique = true;

    return sh._adminCommand( cmd );
}

然后，您可以在MongoDB shell中调用sh._adminCommand：

> sh._adminCommand
function ( cmd , skipCheck ) {
    if ( ! skipCheck ) sh._checkMongos();
    return db.getSisterDB( "admin" ).runCommand( cmd );
}

当你把所有这些放在一起时，所有sh.shardCollection命令都在检查参数并调用这个命令：

db.getSisterDB( "admin" ).runCommand({ 
    shardCollection : "test.a" , 
    key : {"_id": "hashed"}
});

Java语法：

DBObject cmd = new BasicDBObject("shardCollection", "test.a").
  append("key",new BasicDBObject("_id", "hashed"));
CommandResult r = db.getSisterDB("admin").command(cmd);

Answer 2

通过Java api设置分片：

CommandResult result=null; 

// The only way to shard this is via executing a command. If this is not
// done the collection will becreated but it will not be 
// sharded. The first arg is the key and the second one is the logic to be used
final BasicDBObject shardKey = new BasicDBObject("_id", "hashed"); 

final BasicDBObject cmd = new BasicDBObject("shardCollection", "test."+collectionName); 
cmd.put("key", shardKey); 

// RUnning the command to create the sharded collection
result = mongoClient.getDB("admin").command(cmd); 
System.out.println("Collection created successfully");

// loading the collection and then will be insterting the data
final DBCollection shardCollection = mongoClient.getDB("test").getCollection(collectionName); 

// Here i am using a arraylist values which has all the data
shardCollection.insert(values);
System.out.println("Collection added");

Answer 3

没有API。您必须发出命令来设置该分片键。

使用MongoDB Java Driver以编程方式设置分片键

3 个答案: