MongoDB $ in by _id查詢的速度

Question

我想收集1,000個文檔，我通過向單個find（）查詢的$ in操作符傳遞1,000個唯一_id鍵來指定這些文檔。

這比我運行1,000 find（{_ id：}）查詢要快多少？

Answer 1

像這樣的東西應該幫助

//create some data (100k documents) 
for(i=0; i<=100000; i++){ 
    db.foo.insert({"_id":i}); 
} 

//generate some ids to search for 
var ids = []; 
for(i=0; i<=1000; i++){ 
    ids.push(i); 
} 

//now let's try the two queries 

//#1 - 1000 separate find queries 

var timer1Start = new Date().getTime(); //start the stopwatch 

ids.forEach(function(i){ 
    var result = db.foo.find({"_id":i}); 
}); 

var timer1End = new Date().getTime(); //stop the stopwatch 

//#2 $in query 
var timer2Start = new Date().getTime(); //start the stopwatch 
var result = db.foo.find({"_id": {$in: ids}}); 
var timer2End = new Date().getTime(); //stop the stopwatch 

print("Function #1 = " + (timer1Start - timer1End)); 
print("Function #2 = " + (timer2Start - timer2End));