Question

如何使用mongoose对一个100万+的mongodb的表进行遍历操作

Answer 1

var MongoClient = require('mongodb').MongoClient;
var url='mongodb://localhost/sample';
MongoClient.connect(url, function(err, db) {
if(err) { return console.log("connection failed: %s",err); }
console.log('connected to mongo, ready for duty work');
var collection=db.collection('files');
//setInterval(function(){ console.log('memroy usage : %j',process.memoryUsage());},10000);
/** fetch all records **/
var stream=collection.find().stream(),cache=[];
stream.on('data',function(item){
cache.push(item);
if(cache.length==10){
/** signal mongo to pause reading **/
stream.pause();
process.nextTick(function(){
doLotsWork(cache,function(){
cache=[];
/** signal mongo to continue, fetch next record **/
stream.resume();
});
});
}
});
stream.on('end',function(){ console.log('query ended'); });
stream.on('close',function(){ console.log('query closed'); });
});

function doLotsWork(records,callback){
//.....do lots of work
//.....
//all done, ready to deal with next 10 records
process.nextTick(function(){
callback();
});
}