MongoDb update write error: Cannot create field 'category' in element {: null}

[Wz]

I am trying to update embedded document in mongodb using $set. Gives error write error Cannot create field 'category' in element {: null} if update array of json.

Initially document:

db.testdata.find().pretty()
{
    "_id" : ObjectId("5afe722a8a72eab1deb77a99"),   
    "device_type" : "pharmacy",
    "parameters" : [{
        "category" : "Azelastine and Fluticasone",
        "code" : "P7852334",
        "description" : "Seasonal allergic rhinitis",
        "subcategory" : ""
    },
    {
        "category" : "Azithromycin",
        "code" : "P7852336",
        "description" : "Bacterial infections of respiratory tract",
        "subcategory" : ""
    } ]
}

if replace and add few elements in parameter array it works:

db.testdata.update({ device_type: "pharmacy" }, { $set: { "parameters.0.code":"P7852342","parameters.0.category":"Azelastine and Fluticasone","parameters.0.subcategory":"","parameters.0.description":"Seasonal allergic rhinitis","parameters.1.code":"P7852343","parameters.1.category":"Azithromycin","parameters.1.subcategory":"","parameters.1.description":"Bacterial infections of respiratory tract","parameters.2.code":"P7852344","parameters.2.category":"Azilsartan Medoxomil","parameters.2.subcategory":"","parameters.2.description":"Hypertension","parameters.3.code":"P7852345","parameters.3.category":"Cetrizine Hydrochloride.","parameters.3.subcategory":"","parameters.3.description":"Cold and allergy","parameters.4.code":"P7852346","parameters.4.category":"Artemether and Lumefantrine","parameters.4.subcategory":"","parameters.4.description":"Malaria","parameters.5.code":"P7852347","parameters.5.category":"Aspirin","parameters.5.subcategory":"","parameters.5.description":"Pain and inflammation" } })

But unable to add larger array like 14 elements:

db.testdata.update({ "device_type" : "pharmacy" }, { $set: {"parameters.0.code":"P7852342","parameters.0.category":"Azelastine and Fluticasone","parameters.0.subcategory":"","parameters.0.description":"Seasonal allergic rhinitis","parameters.1.code":"P7852343","parameters.1.category":"Azithromycin","parameters.1.subcategory":"","parameters.1.description":"Bacterial infections of respiratory tract","parameters.2.code":"P7852344","parameters.2.category":"Azilsartan Medoxomil","parameters.2.subcategory":"","parameters.2.description":"Hypertension","parameters.3.code":"P7852345","parameters.3.category":"Cetrizine Hydrochloride.","parameters.3.subcategory":"","parameters.3.description":"Cold and allergy","parameters.4.code":"P7852346","parameters.4.category":"Artemether and Lumefantrine","parameters.4.subcategory":"","parameters.4.description":"Malaria","parameters.5.code":"P7852347","parameters.5.category":"Aspirin","parameters.5.subcategory":"","parameters.5.description":"Pain and inflammation","parameters.6.code":"P7852348","parameters.6.category":"Aripiprazole","parameters.6.subcategory":"","parameters.6.description":"Schizophrenia and depression","parameters.7.code":"P7852349","parameters.7.category":"Bambuterol","parameters.7.subcategory":"","parameters.7.description":"Chronic bronchial asthma","parameters.8.code":"P7852350","parameters.8.category":"Beclomethasone Dipropionate","parameters.8.subcategory":"","parameters.8.description":"Corticosteroid and anti-inflammatory","parameters.9.code":"P7852351","parameters.9.category":"Benazepril","parameters.9.subcategory":"","parameters.9.description":"High blood pressure","parameters.10.code":"P7852352","parameters.10.category":"Desipramine","parameters.10.subcategory":"","parameters.10.description":"Antidepressant","parameters.11.code":"P7852353","parameters.11.category":"Diazepam","parameters.11.subcategory":"","parameters.11.description":"Anti anxiety","parameters.12.code":"P7852354","parameters.12.category":"Dicycloverine Hydrochloride","parameters.12.subcategory":"","parameters.12.description":"Gastrointestinal tract spasm","parameters.13.code":"P7852355","parameters.13.category":"Dilazep","parameters.13.subcategory":"","parameters.13.description":"Coronary heart disease","parameters.14.code":"P7852356","parameters.14.category":"Metaraminol","parameters.14.subcategory":"","parameters.14.description":"Spinal anesthesia","parameters.15.code":"P7852357","parameters.15.category":"Methenamine Hippurate","parameters.15.subcategory":"","parameters.15.description":"Urinary tract infections","parameters.16.code":"P7852358","parameters.16.category":"Valbenazine","parameters.16.subcategory":"","parameters.16.description":"Nervous system disorder","parameters.17.code":"P7852359","parameters.17.category":"Vasopressin","parameters.17.subcategory":"","parameters.17.description":"Control of variceal bleeding","parameters.18.code":"P7852360","parameters.18.category":"Warfarin","parameters.18.subcategory":"","parameters.18.description":"Deep venous thrombosis and pulmonary embolism","parameters.19.code":"P7852361","parameters.19.category":"Zolmitriptan","parameters.19.subcategory":"","parameters.19.description":"Migraine","parameters.20.code":"P7852362","parameters.20.category":"Zuclopenthixol","parameters.20.subcategory":"","parameters.20.description":"Mental health disorder","parameters.21.code":"P7852363","parameters.21.category":"Papaverine","parameters.21.subcategory":"","parameters.21.description":"Smooth muscle spasm, cerebral and peripheral ischemia","parameters.22.code":"P7852364","parameters.22.category":"Perindopril","parameters.22.subcategory":"","parameters.22.description":"High blood pressure, heart attack and heart failure","parameters.23.code":"P7852365","parameters.23.category":"Phenazoppyridine","parameters.23.subcategory":"","parameters.23.description":"Urinay tract analgesic" } })
WriteResult({
    "nMatched" : 0,
    "nUpserted" : 0,
    "nModified" : 0,
    "writeError" : {
        "code" : 28,
        "errmsg" : "Cannot create field 'category' in element {: null}"
    }
})

[Kevin Adistambha]

Hi

For the update operation you’re doing, it’s best not to depend on the dot notation syntax for the $set operation, because it can create ambiguity.

For example, if the document doesn’t have the named field:

> db.test2.find()
{
  "_id": 0
}

> db.test2.update({_id:0}, {$set: {"parameters.0.code": "123", "parameters.0.category": "456"}})
Updated 1 existing record(s) in 2ms
WriteResult({"nMatched": 1, "nUpserted": 0, "nModified": 1})

> db.test2.find()
{
  "_id": 0,
  "parameters": {
    "0": {
      "category": "456",
      "code": "123"
    }
  }
}

Note that instead of creating an array inside the parameters field, it created a sub-document with 0 as key instead.

This would be quite different if the parameters field exists with an empty array:

> db.test3.find()
{
  "_id": 0,
  "parameters": [ ]
}

> db.test3.update({_id:0}, {$set: {"parameters.0.code": "123", "parameters.0.category": "456"}})
Updated 1 existing record(s) in 2ms
WriteResult({"nMatched": 1, "nUpserted": 0, "nModified": 1})

> db.test3.find()
{
  "_id": 0,
  "parameters": [
    {
      "category": "456",
      "code": "123"
    }
  ]
}

In terms of your query, the following syntax should work:

db.testdata.update({ "device_type" : "pharmacy" }, { $set: {"parameters": [{"code": "P7852342", "category": "Azelastine and Fluticasone", "subcategory": "", "description": "Seasonal allergic rhinitis"}, {"code": "P7852343", "category": "Azithromycin", "subcategory": "", "description": "Bacterial infections of respiratory tract"}, {"code": "P7852344", "category": "Azilsartan Medoxomil", "subcategory": "", "description": "Hypertension"}, {"code": "P7852345", "category": "Cetrizine Hydrochloride.", "subcategory": "", "description": "Cold and allergy"}, {"code": "P7852346", "category": "Artemether and Lumefantrine", "subcategory": "", "description": "Malaria"}, {"code": "P7852347", "category": "Aspirin", "subcategory": "", "description": "Pain and inflammation"}, {"code": "P7852348", "category": "Aripiprazole", "subcategory": "", "description": "Schizophrenia and depression"}, {"code": "P7852349", "category": "Bambuterol", "subcategory": "", "description": "Chronic bronchial asthma"}, {"code": "P7852350", "category": "Beclomethasone Dipropionate", "subcategory": "", "description": "Corticosteroid and anti-inflammatory"}, {"code": "P7852351", "category": "Benazepril", "subcategory": "", "description": "High blood pressure"}, {"code": "P7852352", "category": "Desipramine", "subcategory": "", "description": "Antidepressant"}, {"code": "P7852353", "category": "Diazepam", "subcategory": "", "description": "Anti anxiety"}, {"code": "P7852354", "category": "Dicycloverine Hydrochloride", "subcategory": "", "description": "Gastrointestinal tract spasm"}, {"code": "P7852355", "category": "Dilazep", "subcategory": "", "description": "Coronary heart disease"}, {"code": "P7852356", "category": "Metaraminol", "subcategory": "", "description": "Spinal anesthesia"}, {"code": "P7852357", "category": "Methenamine Hippurate", "subcategory": "", "description": "Urinary tract infections"}, {"code": "P7852358", "category": "Valbenazine", "subcategory": "", "description": "Nervous system disorder"}, {"code": "P7852359", "category": "Vasopressin", "subcategory": "", "description": "Control of variceal bleeding"}, {"code": "P7852360", "category": "Warfarin", "subcategory": "", "description": "Deep venous thrombosis and pulmonary embolism"}, {"code": "P7852361", "category": "Zolmitriptan", "subcategory": "", "description": "Migraine"}, {"code": "P7852362", "category": "Zuclopenthixol", "subcategory": "", "description": "Mental health disorder"}, {"code": "P7852363", "category": "Papaverine", "subcategory": "", "description": "Smooth muscle spasm, cerebral and peripheral ischemia"}, {"code": "P7852364", "category": "Perindopril", "subcategory": "", "description": "High blood pressure, heart attack and heart failure"}, {"code": "P7852365", "category": "Phenazoppyridine", "subcategory": "", "description": "Urinay tract analgesic"} ]}})

Having said that, is there a reason why you’re using such a large array?

For schema design considerations, you may find the following links helpful:

• 6 Rules of Thumb for MongoDB Schema Design: Part 1, Part 2, Part 3
• Data Models
• Use Cases

Best regards
Kevin

​

[Whiznets Application]

Hi Kelvin,

In my case, a user who inserted document into mongodb, will take care of schema for document whether its have embedded document of objects or array. If value for a field is an array it must then use array at the time of insertion either empty array or having object of what ever structure he trying to update.

I am using "path" using dot notation with there value to update documents because i do not know what is the schema at my end. A user must know what he inserted before and trying to update now.

Problem:

> db.test3.find()
{ "_id": 0, "parameters": [{ "code": "1", "category": "category 1" }, { "code": "2", "category": "category 2" } ] }

And

> db.test3.update({ _id:0 }, { $set: { parameters: [{ "code": "3", "category": "3" }] }})
{ "_id": 0, "parameters": [{ "code": "3", "category": "3" } ] }

Here is previously parameters field having two element and after update its having one  element that replace previous one.

My requirement is not to replace whole array instead replace element and if number of elements in array is more then add new element is acceptable that's why i used dot notation with path and value to update embedded document.

But when trying to update using path gives error mongodb write error cannot create field category of null.

Please let me know if any thing more need to be share from my side. 

Thanks

 

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[Kevin Adistambha]

Hi

But when trying to update using path gives error mongodb write error cannot create field category of null.

Regarding that error, I have submitted SERVER-35220. Please watch the ticket for updates on this issue.

Best regards
Kevin

​