push an array element if certain element not exists or update in mongodb

Question

I have to update an array inside a document on the basis of a string which i get from the req.value.

My collection

[
  {
    "_id": 1,
    "key": [
      "1-value-1",
      "1-value-2"
    ]
  },
  {
    "_id": 2,
    "key": [
      "2-value-1",
      "2-value-2"
    ]
  }
]

I have another string newString. Let's assume two conditions:

when req.value is in the array in that case replace the array value with newString.
else rew.value is not present simple push the newString in the array.

Eg: I have a newString = 1-value-3 and req.value = 1-value-2 in that case replace array value 1-value-2 to 1-value-3. Else if req.value isn't in array push newString value to array.

This is the collection on which i want to perform operations on.

Thanks for answering in advance.

Please copy the input data directly into this question instead of linking to mongoplayground; it makes it easier for both new readers and answerers. Second: you write update to 1-value-3 if 1-value-2 exists else push 1-value-3 if 1-value-4 doesn't exist That is unclear. Please edit the question to show exactly what the desired output shape should be. — Buzz Moschetti
– Buzz Moschetti, Commented Apr 15, 2022 at 18:01

Takis · Accepted Answer · 2022-04-15 18:52:10Z

3

Update with pipeline

Query

if 1-value-2 exists change to 1-value-3
else `push 1-value-3 in the end of the array (i think you want this)
filter to check if it exists
if exists map to update
else concat to add in the end of the array

Playmongo(update,exists)
Playmongo(push(concat), missing)

update(
{"_id": {"$eq": 1}},
[{"$set": 
   {"v2-exists": 
     {"$ne": 
       [{"$filter": 
           {"input": "$key", "cond": {"$eq": ["$$this", "1-value-2"]}}},
         []]}}},
 {"$set": 
   {"key": 
     {"$cond": 
       ["$v2-exists",
         {"$map": 
           {"input": "$key",
            "in": 
             {"$cond": 
               [{"$eq": ["$$this", "1-value-2"]}, "1-value-3", "$$this"]}}},
         {"$concatArrays": ["$key", ["1-value-3"]]}]}}},
 {"$unset": ["v2-exists"]}])

Update operators

Query1(check if exists)

find({"_id": {"$eq": 1}, "key": {"$elemMatch": {"$eq": "1-value-2"}}})

If query1 empty result send this(push at the end)

update(
{"_id": {"$eq": 1}},
{"$push": {"key": "1-value3"}})

else send this (set to replace the old value)

update(
{"_id": {"$eq": 1}},
{"$set": {"key.$[m]": "1-value-3"}},
{"arrayFilters": [{"m": {"$eq": "1-value-2"}}]})

edited Apr 15, 2022 at 18:52

answered Apr 15, 2022 at 18:08

Takis

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8 Comments

Buzz Moschetti Over a year ago

Where's the update...?

Takis Over a year ago

its ok i fixed that, it was update with pipeline, and i forgot to change the method, the problem is that i am not sure if this is what he wants, if you understand what he wants maybe try to answer i am confused, and just tried.

Buzz Moschetti Over a year ago

What happened to a condition to check for 1-value-4? @ShubhamMaheshwari Expand the question to explain what is going on with the candidate string that is sent to the update.

Takis Over a year ago

i added alternative way, without aggregation update, that you will find probably simpler.Bu t its not atomic. And its 2 queries.

Takis Over a year ago

ok this answer does what you want i think, try one of those 2 ways, and i think you will be ok. if works accept it as solution also, this helps me and others to know if question has working answer.

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