How to optimize this `for` loop update?

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    • Type: Question
    • Resolution: Done
    • Priority: Major - P3
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    • Affects Version/s: None
    • Component/s: JavaScript
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      I want to replace the collection field based on a map table, like

      old_src new_src
      1 448
      5 449
      ... ...

      So I write a very simple JavaScript.

      db_name = 'mydb'
collection_name = 'mycoll'

src_map = [
    [1,448],
    [5,449],
    [6,450],
    [8,451],
    [9,452],
    [10,453],
    [11,454],
    [12,455],
    [14,456],
    [15,457],
    [16,458],
    [17,459],
    [18,460],
    [20,461],
    [22,462],
    [23,463],
    [24,464],
    [25,465],
    [26,466],
    [27,467],
    [29,468]
]

db = db.getSiblingDB(db_name)
for (x in src_map) {
    old2new_map = src_map[x];
    print("Changing src: " + String(old2new_map[0]) + " --> " + String(old2new_map[1]) + " ... ");
    db[collection_name].update({"src":old2new_map[0]},{$set:{"src":old2new_map[1]}},{multi:true});
    print("Done.")
}

      I use update function within a for loop to do this. But it's so slow. This collection contains more than 1000000 objects, and each update will execute more than 10 mins(even if src field has a index).

      How to optimize this script? Is there any way to update the whole may in a single function? Or use multi thread way to let the update function parallelly?

            Assignee:
            Unassigned
            Reporter:
            Feng Yu
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              Created:
              Updated:
              Resolved: