MongoDB JAVA-API执行mapreduce的几种方法

suncool

　　转载自：http://my.oschina.net/huzorro/blog/75210
1> db.version();21.6.31mongodb-2.0.jar0105db.runCommand(  06{  07    mapreduce : ,  08    map : ,  09    reduce :   10    [, query : ]  11    [, sort : ] for 12    [, limit : ] return 13    [, out : ]  14    [, keeptemp: < | >] true false 15    [, finalize : ]  16    [, 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3public MapReduceOutput mapReduce(String map, String reduce, 4                                String outputCollection, 5                                DBObject query) 6                                throws MongoException7//以下两个方法可以使用全部参数列表8public MapReduceOutput mapReduce(DBObject command) throws MongoException9public CommandResult command(DBObject cmd) throws MongoException0104res = 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("$lte", "20120824"));19    MapReduceOutput mro = dbc.mapReduce(mapfun, reducefun, 20                            "tmp_mo_spcode_consignid_region_serviceid_201208_1", query);0104res = db.runCommand({05    mapreduce:'mo_log_201208',06    query:{Logtime:{$gte:'20120823', $lte:'20120824'}},07    map:function() {08        emit({Spcode:this.Spcode, Spname:this.Spname, 09        Consignid:this.Consignid, Consname:this.Consname, 10        Region:this.Region, Regionname:this.Regionname, 11        Serviceid:this.Serviceid, Servicename:this.Servicename, 12        Srctermid:this.Srctermid}, {count:1});13    },14    reduce:function(key, value) {15        var ret = {count:0};16        ret.count++;17        return ret;18    },19    finalize:function(key, value){20        db.tmp_mo_spcode_consignid_region_serviceid_201208.insert({"_id":key, "value":value});21        return value;22    },23    out:'tmp_mo_spcode_consignid_region_serviceid_201208_1',24    verbose:true25})01//JAVA-API mapreduce02    Mongo db = new Mongo("host", "port");03    DBCollection dbc = db.getCollection("mo_log_201208");04    String mapfun = "function() {" +05        "emit({Spcode:this.Spcode, Spname:this.Spname, " +06                "Consignid:this.Consignid, Consname:this.Consname, " +07                "Region:this.Region, Regionname:this.Regionname, " +08                "Serviceid:this.Serviceid, " +   09                "Servicename:this.Servicename, " +10                "Srctermid:this.Srctermid}, {count:1});" +11                "}";12    String reducefun = "function(key, value) {" +13        "var ret = {count:0};" +14        "ret.count++;" +15        "return ret;" +16        "}";17    String finalizefun = "function(key, value){" +18        "db.tmp_mo_spcode_consignid_region_serviceid_201208.insert({"_id":key, "value":value});" +19        "return value;" +20        "}";21    DBObject query = new BasicDBObject("Logtime", 22                        new BasicDBObject("$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mapreduce32    MapReduceOutput mro = dbc.mapReduce(command);33    //在db上使用command执行mapreduce34    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