MongoDB JAVA-API执行mapreduce的几种方法

转载自：http://my.oschina.net/huzorro/blog/75210

1	> db.version();

2

1.6.3

1	mongodb-2.0.jar

01

<!--

02	#shell下完整的参数列表

03	#更高版本会多几个参数

04

//-->

05	db.runCommand(

06

{

07	mapreduce : <collection>,

08	map : <mapfunction>,

09	reduce : <reducefunction>

10	[, query : <query filter object>]

11	[, sort : <sort the query.  useful   optimization>] for

12	[, limit : <number of objects to   from collection>] return

13	[, out : <output-collection name>]

14	[, keeptemp: < | >] true false

15	[, finalize : <finalizefunction>]

16	[, scope : <object where fields go into javascript global scope >]

17	[, verbose :  ] true

18

});

1	//JAVA-API中可以执行mapreduce的方法

2	//该方法只允许携带4个参数

3	public MapReduceOutput mapReduce(String map, String reduce,

4	String outputCollection,

5	DBObject query)

6	throws MongoException

7	//以下两个方法可以使用全部参数列表

8	public MapReduceOutput mapReduce(DBObject command) throws MongoException

9	public CommandResult command(DBObject cmd) throws MongoException

 

01

<!--

02	#shell mapreduce

03

//-->

04	res = db.runCommand({

05	mapreduce:'mo_log_201208',

06	query:{Logtime:{$gte:'20120823', $lte:'20120824'}},

07	map:function() {

08	emit({Spcode:this.Spcode, Spname:this.Spname,

09	Consignid:this.Consignid, Consname:this.Consname,

10	Region:this.Region, Regionname:this.Regionname,

11	Serviceid:this.Serviceid,

12	Servicename:this.Servicename,

13	Srctermid:this.Srctermid}, {count:1});

14

},

15	reduce:function(key, value) {

16	var ret = {count:0};

17	ret.count++;

18	return ret;

19

},

20	out:'tmp_mo_spcode_consignid_region_serviceid_201208_1'

21

})

01	//JAVA-API mapreduce

02	Mongo db = new Mongo("host", "port");

03	DBCollection dbc = db.getCollection("mo_log_201208");

04	String mapfun = "function() {" +

05	"emit({Spcode:this.Spcode, Spname:this.Spname, " +

06	"Consignid:this.Consignid, Consname:this.Consname, " +

07	"Region:this.Region, Regionname:this.Regionname, " +

08	"Serviceid:this.Serviceid, " +

09	"Servicename:this.Servicename, " +

10	"Srctermid:this.Srctermid}, {count:1});" +

11

"}";

12	String reducefun = "function(key, value) {" +

13	"var ret = {count:0};" +

14	"ret.count++;" +

15	"return ret;" +

16

"}";

17	DBObject query = new BasicDBObject("Logtime",

18	new BasicDBObject("$gte", "20120823").append("$lte", "20120824"));

19	MapReduceOutput mro = dbc.mapReduce(mapfun, reducefun,

20	"tmp_mo_spcode_consignid_region_serviceid_201208_1", query);

01

<!--

02	#该mapreduce比上一个多了两个参数

03

//-->

04	res = db.runCommand({

05	mapreduce:'mo_log_201208',

06	query:{Logtime:{$gte:'20120823', $lte:'20120824'}},

07	map:function() {

08	emit({Spcode:this.Spcode, Spname:this.Spname,

09	Consignid:this.Consignid, Consname:this.Consname,

10	Region:this.Region, Regionname:this.Regionname,

11	Serviceid:this.Serviceid, Servicename:this.Servicename,

12	Srctermid:this.Srctermid}, {count:1});

13

},

14	reduce:function(key, value) {

15	var ret = {count:0};

16	ret.count++;

17	return ret;

18

},

19	finalize:function(key, value){

20	db.tmp_mo_spcode_consignid_region_serviceid_201208.insert({"_id":key, "value":value});

21	return value;

22

},

23	out:'tmp_mo_spcode_consignid_region_serviceid_201208_1',

24	verbose:true

25

})

01	//JAVA-API mapreduce

02	Mongo db = new Mongo("host", "port");

03	DBCollection dbc = db.getCollection("mo_log_201208");

04	String mapfun = "function() {" +

05	"emit({Spcode:this.Spcode, Spname:this.Spname, " +

06	"Consignid:this.Consignid, Consname:this.Consname, " +

07	"Region:this.Region, Regionname:this.Regionname, " +

08	"Serviceid:this.Serviceid, " +

09	"Servicename:this.Servicename, " +

10	"Srctermid:this.Srctermid}, {count:1});" +

11

"}";

12	String reducefun = "function(key, value) {" +

13	"var ret = {count:0};" +

14	"ret.count++;" +

15	"return ret;" +

16

"}";

17	String finalizefun = "function(key, value){" +

18	"db.tmp_mo_spcode_consignid_region_serviceid_201208.insert({"_id":key, "value":value});" +

19	"return value;" +

20

"}";

21	DBObject query = new BasicDBObject("Logtime",

22	new BasicDBObject("$gte", "20120823").append("$lte", "20120824"));

23	DBObject command = new BasicDBObject();

24	command.put("mapreduce", "mo_log_201208");

25	command.put("query", query);

26	command.put("map", mapfun);

27	command.put("reduce", reducefun);

28	command.put("finalize", finalizefun);

29	command.put("out", "tmp_mo_spcode_consignid_region_serviceid_201208_1");

30	command.put("verbose", true);

31	//在dbcollection上执行mapreduce

32	MapReduceOutput mro = dbc.mapReduce(command);

33	//在db上使用command执行mapreduce

34	CommandResult cr = db.command(command);

>>以上3种方法都可以执行mapreduce, 参数和返回结果各不相同, 根据自己的需要和使用习惯选择合适的方法
>>新版的Mongodb增加了新的聚合框架, 有更多的参数选择, 参见Aggregation Framework