為了營造大批量數據,我們可以這樣寫javascript腳本
for (var i=1;i<=10000;i++) { if(i%2==1) { db.cursortest.insert({_id:i,name:'程勁'+i,age:19,major:['泰拳','散打','巴西柔術','和saintding大哥玩SM']}); } else if(i%2==0) { db.cursortest.insert({_id:i,name:'陳培昌'+i,age:21,major:['泰拳','散打','巴西柔術','和saintding大哥一起廝混']}); } }
顯然,這樣海量的數據,需要cursor幫助我們完成查詢
可以指定只顯示前10行
var mycursor = db.cursortest.find({_id:{$lte:10}})
mycursor.next()依次取下一條
當然mongodb為我們封裝了forEach函數來循環打印結果注意大小寫:
mycursor.forEach(function(obj){printjson(obj)})
效果如下:
還有分頁的功能:
var duwa = db.cursortest.find().skip(9990)
duwa.forEach(function(obj){printjson(obj)})
1 var tianwadi = db.cursortest.find().skip(9990).limit(5) 2 tianwadi.forEach(function(obj){printjson(obj)})
跨過前9990行,只顯示5條
下面使用游標的toArray()方法,結果卧操~
注意!無論在命令行還是類似studio3T這樣的IDE,在每次執行完游標的操作后,游標已經窮盡了數據集,所以要通過再聲明一次游標的方法,以確保游標的forEach操作能繼續進行。
var tianwadi = db.cursortest.find().skip(9990).limit(5) tianwadi.toArray()
輸出結果會返回一個列表,如下:
[ { "_id" : 9991, "name" : "程勁9991", "age" : 19, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥玩SM" ] }, { "_id" : 9992, "name" : "陳培昌9992", "age" : 21, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥一起廝混" ] }, { "_id" : 9993, "name" : "程勁9993", "age" : 19, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥玩SM" ] }, { "_id" : 9994, "name" : "陳培昌9994", "age" : 21, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥一起廝混" ] }, { "_id" : 9995, "name" : "程勁9995", "age" : 19, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥玩SM" ] } ]
如果只取列表中的第4條操作如下:
var tianwadi = db.cursortest.find().skip(9990).limit(5)
tianwadi.toArray()[4]
返回結果如下;
{ "_id" : 9995, "name" : "程勁9995", "age" : 19, "major" : [ "泰拳", "散打", "巴西柔術", "和丁大哥玩SM" ] }