In MongoDB there is the maximum size of 16 MByte per document. Does this size limit include sub-documents?
In other words: Are the 16 MByte per document including its sub-documents, or is it 16 MByte per document and each sub-document counts as an own document?
Yes, this is 16MB limit for the whole structure, including sub-documents.
Keep in mind that what you call sub-documents, MongoDB sees as regular values. From its perspective, they are no different than, say, strings. Just values.
Related
Is there any limit for fields count per single MongoDB document? Didn't find anything about that in documentation.
For example, if I have document that contains 1000 fields and fits 16Mb.
Yes, It will work.
Fields are part of Documents. Mongo has only document size limit of 16Mb. As long as it fits in 16Mb, it's good.
But I suggest you to look at the need for these many fields in single document.
Does MongoDB 16MB limit apply to a single denormalized db document, or to each embedded document in particular? In one-to-many relationships with embedded documents, do all the "many" documents have to be less than 16 MB in size altogether?
I'm asking this because I can't choose my data model yet - Its recommended for "contains" relationships (which is exactly my case) to stick to the denormalized strategy, but I believe the sub-documents will exceed 16 MB in sum. Will that work?
One whole doc, regardless of the complexity of the shape and level of embedding, if any, cannot exceed 16MB.
I am planning to save huge number of ids for foreignkey ids in this array. So, I am just checking what would be the max number of BSON::ObjectIds I can save in the field array. Lets say for example
department_ids: [BSON::OBjectId('57cf6d6e8315292136000001'), BSON::OBjectId('57cf6d6e8315292136000002') ...... ]
16MB is big enough to hold really large amount of ObjectId, ObjectIds aren't that heavy, they are 12 bytes and when you divide it by 16MB you get well beyond 1 million.
But in case you still aren't assured, you can benefit by the flexible schema design of Mongo and create one follow-up document to hold further arrays and store the _id of that document in the concerned document with a field named as "followedBy" or something.
downside is you will have to execute a follow-up query (or maybe not).
Hope that helps.
No such limit mentioned in documents of monogdb for it but a javascript array can have upto 2^32-1 = 4,294,967,295 = 4.29 billion elements.
And mongodb document could have upto 16MB.
Every ObjectID uses 12 bytes, if the limit is 16 MB you could have approximately 1398101 objectsID in a array per document.
Maybe the DBRefs could help you, or you could use a GridFS collection.
If you could avoid the joins that would be the best solution on mongo.
Edited 1st July 2021
Since the document that contains the array can not exceed 16 megabytes, the number of objects in an array is limited.
The other answers explain how to calculate this.
MongoDB Limits and Thresholds
I haven't found any information about this.
How many documents can a single collection have in MongoDB before it is necessary to use sharding?
There is no limitation as you can see here:
If you specify a maximum number of documents for a capped collection using the max parameter to create, the limit must be less than 2^32 documents. If you do not specify a maximum number of documents when creating a capped collection, there is no limit on the number of documents.
#M-A.Fernandes has right.
I can only add this information:
Maximum Number of Documents Per Chunk to Migrate
MongoDB cannot move a chunk if the number of documents in the chunk exceeds either 250000 documents or 1.3 times the result of dividing the configured chunk size by the average document size. db.collection.stats() includes the avgObjSize field, which represents the average document size in the collection.
This is about a recommendation on mongodb. I have a collection that always increase row by row (I mean the count of documents). It is about 5 billion now. When I make a request on this collection I sometimes get the error about 16 MB size.
The first thing that I want to ask is which structure is the best way of creating collections that increasing the rows hugely. What is the best approach? What should I do for this kind of structure and the performance?
Just to clarify, the 16MB limitation is on documents, not collections. Specifically, its the maximum BSON document size, as specified in this page in the documentation.
The maximum BSON document size is 16 megabytes.
If you're running into the 16MB limit in aggregation is because you are using MongoDB version 2.4 or older. In these, the aggregate() method returned a document, which is subject to the same limitation as all other documents. Starting in 2.6, the aggregate() method returns a cursor, which is not subject to the 16MB limit. For more information, you should consult this page in the documentation. Note that each stage in the aggregation pipeline is still limited to 100MB of RAM.