I had a collection with an embedMany attribute using strategy=set, so an ArrayCollection was stored. However we deleted some items from the array and now there are some documents with keys not sequential integers.
I need to solve this inconsistence, how can I do that?
You could use $type operator and query for all documents where your embedManyField is of type object. Once you have these documents, apply array_values to fields where array shall be stored and save them again. Also to avoid such situations in future you should change your collection's strategy to either setArray or atomicSetArray.
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.
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.
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 two type of documents in a mongodb collection:
one where key sessions has a simple value:
{"sessions": NumberLong("10000000000001")}
one where key sessions has an array of values.
{"sessions": [NumberLong("10000000000001")]}
Is there any way to retrieve all documents from the second category, ie. only documents whose value is an arary and not a simple value?
You can use this kind of query for that:
db.collectionName.find( { $where : "Array.isArray(this.sessions)" } );
but you'd better convert all the records to one type to keep the things consistent.
This code can be simple like this:
db.c.find({sessions:{$gte:[]}});
Explanation:
Because you only want to retrieve documents whose sessions data type is array, and by the feature of $gte (if data types are different between tow operands, it returns false; Double, Integer32, Integer64 are considered as same data type.), giving an empty array as the opposite operand will help to retrieve all results by required.
Also , $gt, $lt, $lte for standard query (attention: different behaviors to operaors with same name in expression of aggregation pipeline) have the same feature. I proved this by practice on MongoDB V2.4.8, V2.6.4.
I'm building a database with several collections. I have unique strings that I plan on using for all the documents in the main collection. Documents in other collections will reference documents in the main collection, which means I'll have to save said id's in the other collections. However, if _id's only need to be unique across a collection and not across an entire database, then I would just make the _id's in the other collections also use the aforementioned unique strings.
Also, I assume that in order to set my own _id's, all I have to do is have an "_id":"unique_string" property as part of the document that I insert, correct? I wouldn't need to convert the "unique_string" into another format, right?
Also, hypothetically speaking, would I be able to have a variable save the string "_id" and use that instead? Just to be clear, something as follows: var id = "_id" and then later on in the code (during an insert or a query for example) have id:"unique_string".
Best, and thanks,Sami
_ids have to be unique in a collection. You can quickly verify this by inserting two documents with the same _id in two different collections.
Your other assumptions are correct, just try them and see whether they work (they will). The proof of the pudding is in the eating.
Note: use _id directly, var id = "_id" just compilcates the code.