mongodb update on JSON array

Question

I have this data in Mongo:

{'_id':1,
             'name':'Root',
             'taskId':1,
             'parentId':"",
             'path':[1],
             'tasks':[  {"taskId":3,parentId:1,name:'A',type:'task'},
                        {"taskId":4,parentId:1,name:'D',type:'task'},
                        {"taskId":5,parentId:4,name:'B',type:'task'},
                        {'type':'project' , 'proRef':2},
                        {"taskId":6,parentId:3,name:'E',type:'task'},
                        {"taskId":7,parentId:6,name:'C',type:'task'}]

            }

Now I want to update taskId 6 with new Json data .

var jsonData = {"taskId":6,"name":'Sumeet','newField1':'Val1','newField2':'Val2'}

query should update if field is available else add new key to existing .Output Like

{"taskId":6,parentId:3,name:'Sumeet',type:'task','newField1':'Val1','newField2':'Val2'}]

I have tried few query but it is completely replacing json .

 db.projectPlan.update({_id:1,'tasks.taskId':6},{$set :{'tasks.$':jsonData }});

Thanks in advance for your helps! Sumeet

That's strange. According to the documentation it should work. — Philipp
– Philipp, Commented Dec 12, 2013 at 20:50
Indeed this query will only replace the task with taskId 6. It will not merge the existing data with the new data. See my solution below for how the data can be merged. — user152468
– user152468, Commented Dec 12, 2013 at 21:17

Asya Kamsky · Accepted Answer · 2013-12-13 02:10:48Z

You need to transform the jsonData variable into something that can be passed to update. Here's an example that does exactly what you want with your sample document:

var updateData = {};
for (f in jsonData) {
    if (f != "taskId") updateData["tasks.$."+f]=jsonData[f]; 
};
db.projectPlan.update({_id:1, 'tasks.taskId':6}, {$set:updateData})

Result:

{ "_id" : 1, 
  "name" : "Root",
  "taskId" : 1,
  "parentId" : "",
  "path" : [  1 ],
  "tasks" : [
    {   "taskId" : 3,   "parentId" : 1,     "name" : "A",   "type" : "task" },
    {   "taskId" : 4,   "parentId" : 1,     "name" : "D",   "type" : "task" },
    {   "taskId" : 5,   "parentId" : 4,     "name" : "B",   "type" : "task" },
    {   "type" : "project",     "proRef" : 2 },
    {   "taskId" : 6,   "parentId" : 3,     "name" : "Sumeet",  "type" : "task",    "newField1" : "Val1",   "newField2" : "Val2" },
    {   "taskId" : 7,   "parentId" : 6,     "name" : "C",   "type" : "task" } 
] }

user152468 · Accepted Answer · 2013-12-13 08:04:43Z

1

You will need to merge the document manually:

var jsonData = {"taskId":5,"name":'Sumeet','newField1':'Val1','newField2':'Val2'};

db.projectPlan.find({ _id: 1 }).forEach(
  function(entry) {
    for (var taskKey in entry.tasks) {
      if (entry.tasks[taskKey].taskId === jsonData.taskId) {
        printjson(entry.tasks[taskKey]);
        for (var taskSubKey in jsonData) {
           entry.tasks[taskKey][taskSubKey] = jsonData[taskSubKey];
        }
        printjson(entry.tasks[taskKey]);
      }
    }
    db.projectPlan.save(entry);
  }
);

Obviously you can leave away the printjson statements. This is simply to see that the merging of the original tasks with the new tasks works. Note that this query will only update a single document as long as the _id field is unique.

edited Dec 13, 2013 at 8:04

answered Dec 12, 2013 at 21:06

user152468

3,2627 gold badges31 silver badges60 bronze badges

6 Comments

Asya Kamsky Over a year ago

this is completely unnecessary - why would you need to look at every single document?

user152468 Over a year ago

this solution only looks at documents with '_id: 1'. Usually this field has index support. So this query will be fast.

Asya Kamsky Over a year ago

then why have all the javascript to do the update when it can be done atomically and thread-safe on the server? If your code is run twice, it may lose one of the update's changes since your query and your save are not atomic.

user152468 Over a year ago

If the same code runs twice, the answer will be the same since the operation is idempotent (only if the input stays the same). Yet I agree that atomicity is a plus, and therefore I like your solution. This solution is, however, more extensible.

Asya Kamsky Over a year ago

I'm talking about two threads trying to update the same object (but different tasks of the same object). They will both read the document and then both save and the one that saves second will overwrite the changes of the first one.

|

Collectives™ on Stack Overflow

mongodb update on JSON array

2 Answers 2

Comments

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related