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.
Related
There is a document with array, which size is more than 16 MB. How to store this document to be able to query some data from this array.
When you have documents which exceed the 16MB limit then you are very likely taking the denormalization approach of MongoDB too far and should consider to create another collection with one document for each array entry (or one document for each sensible grouping of array entries).
Another option is to treat the content as binary data and store it as a file in GridFS, but then you won't be able to do any meaningful queries on its content (only on the metadata you write for it separately).
The 16MB limit is hardcoded. You can not change it through configuration. There was a bugtracker ticket for that and it was closed as "Won't fix". But considering that MongoDB is open source, you could always change it in the sourcecode. Just keep the license conditions in mind when you do that.
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.
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.
what I have ?
I have data of 'n' department
each department has more than 1000 datasets
each datasets has more than 10,000 csv files(size greater than 10MB) each with different schema.
This data even grow more in future
What I want to DO?
I want to map this data into mongodb
What approaches I used?
I can't map each datasets to a document in mongo since it has limit of 4-16MB
I cannot create collection for each datasets as max number of collection is also limited (<24000)
So finally I thought to create collection for each department , in that collection one document for each record in csv file belonging to that department.
I want to know from you :
will there be a performance issue if we map each record to document?
is there any max limit for number of documents?
is there any other design i can do?
will there be a performance issue if we map each record to document?
mapping each record to document in mongodb is not a bad design. You can have a look at FAQ at mongodb site
http://docs.mongodb.org/manual/faq/fundamentals/#do-mongodb-databases-have-tables .
It says,
...Instead of tables, a MongoDB database stores its data in collections,
which are the rough equivalent of RDBMS tables. A collection holds one
or more documents, which corresponds to a record or a row in a
relational database table....
Along with limitation of BSON document size(16MB), It also has max limit of 100 for level of document nesting
http://docs.mongodb.org/manual/reference/limits/#BSON Document Size
...Nested Depth for BSON Documents Changed in version 2.2.
MongoDB supports no more than 100 levels of nesting for BSON document...
So its better to go with one document for each record
is there any max limit for number of documents?
No, Its mention in reference manual of mongoDB
...Maximum Number of Documents in a Capped Collection Changed in
version
2.4.
If you specify a maximum number of documents for a capped collection
using the max parameter to create, the limit must be less than 232
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 ...
is there any other design i can do?
If your document is too large then you can think of document partitioning at application level. But it will have high computation requirement at application layer.
will there be a performance issue if we map each record to document?
That depends entirely on how you search them. When you use a lot of queries which affect only one document, it is likely even faster that way. When a higher document-granularity results in a lot of document-spanning queries, it will get slower because MongoDB can't do that itself.
is there any max limit for number of documents?
No.
is there any other design i can do?
Maybe, but that depends on how you want to query your data. When you are content with treating files as a BLOB which is retrieved as a whole but not searched or analyzed on the database level, you could consider storing them on GridFS. It's a way to store files larger than 16MB on MongoDB.
In General, MongoDB database design doesn't depend so much on what and how much data you have, but rather on how you want to work with it.
I understand that in MongoDB a BSON document can be no bigger than 16mb. Does this size limit account for embedded documents as well? I plan on having well over 16mb of documents inside the embedding document.
A single MongoDB document cannot be larger than 16 MB and all of a document's embedded documents count toward this limit, so what you're planning won't work.