We have two documents that have merged and they now have one one ObjectId.
There exists a configuration document that may have references to the old ObjectId. The old ObjectID can exist all over this document which is full of nested arrays and lists.
We want to do a simple find and replace on this document, preferably without replacing the entire document itself.
Is there a generic way to set every field that has ObjectIdA as a value and replace it with ObjectIdB?
There's no way to do that, no. You need to perform updates on all possible paths explicitly.
Related
Example :[{
inst:"EVA",
std:"12th"
},
{
inst:"KSF",
std:"12th"
}]
As per the above example, In my case if "inst: "EVA" is already there in the "qualification" array so we need to update the object from the existing one.
Then "inst: "KSF" does not already exist in the "qualification" array so we need to add that one.
Help me if there is any way to upsert using firestore query.
There is no "upsert" operation for objects in arrays. If you need to make changes to that array, you will have to read the document, modify the contents of the array in memory, then update the document with the new contents of the array.
Arrays of objects usually do not work the way that people want, given their limitations on querying and updating. It's usually better to store data as documents in a nested subcollection, so they can be more easily queried and updated by the contents of their fields.
I would like to encode some meaning behinds first N characters of every document ID i.e. make first three characters determine a document type sensible to the system being used in.
You can have a custom _id when you insert the document. If the document to be inserted doesn't contain _id, then MongoDB will insert a ObejctId for you.
The _id can be of any type but keeping it uniform for all the documents makes sense if you are accessing from application layer.
You can refer one of the old questions at SO - How to generate unique object id in mongodb
In MongoDB, you can use db.collection.save({_id:'abc'}, objectToSave) to perform an upsert.
Let's define objectToSave as below
{_id:'abc', field1:1, field2:2};
In my collection, I have already have a document with same _id value as below:
{_id:'abc', field3:3};
The save function above will replace the existing document in collection to
{_id:'abc', field1:1, field2:2};
What I want is to perform a $set operation to produce some document in collection as below
{_id:'abc', field1:1, field2:2, field3:3};
Can this be achieved in the save function or I have to write separate update statements?
Note that objectToSave's fields are dynamic. The language I'm using is Node.JS.
db.collection.update({'_id':'abc'},{$set:{field1:1,field2:2}},{upsert:true})
should do what you want:
It upserts, so if the document does not exist yet, it is created as {_id:'abc',field1:1,field2:2} and efficiently so, since an index is used which must exist
If the document already exists, the fields field1 and field2 are set to the value in the update statement.
If either of the fields exist in the document, it will be overwritten.
Since you didn't state what language you use: in plain mongoDB, there is no save function. The explicit requirement to merge new and persisted versions of entities is quite an unusual one, so yes, I'd assume that you have to write a custom function.
I have collections with huge amount of Documents on which I need to do custom search with various different queries.
Each Document have boolean property. Let's call it "isInTop".
I need to show Documents which have this property first in all queries.
Yes. I can easy do sort in this field like:
.sort( { isInTop: -1 } );
And create proper index with field "isInTop" as last field in it. But this will be work slowly, as indexes in mongo works best with unique fields.
So is there is solution to show Documents with field "isInTop" on top of each query?
I see two solutions here.
First: set Documents wich need to be in top the _id from "future". As you know, ObjectId contains timestamp. So I can create ObjectId with timestamp from future and use natural order
Second: create separate collection for Ducuments wich need to be in top. And do queries in it first.
Is there is any other solutions for this problem? Which will work fater?
UPDATE
I have done this issue with sorting on custom field which represent rank.
Using the _id field trick you mention has the problem that at some point in time you will reach the special time, and you can't change the _id field (without inserting a new document and removing the old one).
Creating a special collection which just holds the ones you care about is probably the best option. It gives you the ability to logically (and to some extent, physically) separate the documents.
Newly introduced in mongodb there is also support for a "sparse" index which may fulfill your needs as well. You could only set the "isInTop" field when you want it to be special, and then create a sparse index on it which would not have the problems you would normally have with a single indexed boolean field (in btrees).
I want to do a batch insert in mongodb , but if the record exists already it should replace it with the new one.There is update command but its not possible to do it in batch.Any idea whether it is possible? I am using java api.
Thanks
Edit:
As my collection size is not very huge, i am renaming the collection with drop Target option set to true and creating a new collection with this data.As i cant risk deleting and creating a new collection this is better, but it will be awesome if there is replace into equivalent.
If you are having any primary key in your collection, then it will replace automatically.Make sure your documents have _id key.
Look at mongodb document:
Shorthand for insert/update is save - if _id value set, the record is updated if it exists or inserted if it does not; if the _id value is not set, then the record is inserted as a new one.
in http://mongodb.github.io/node-mongodb-native/markdown-docs/insert.html