Menu
In my database I have to store an array of object ids. What should I use? Something like this:
[ObjectId("50350e12a36feb1be6000364"), ObjectId("57350e12a37fef1be6000922"), ObjectId("10350e17d34ffb1be6200925")]
or something like this:
["50350e12a36feb1be6000364", "57350e12a37fef1be6000922", "10350e17d34ffb1be6200925"]
I could save space with the second, and then cast to ObjectId, but am I loosing anything by using this approach? Do ObjectIds behave like foreign keys in relational databases?
283
One of the benefits of MongoDB's rich schema model is the ability to store arrays as document field values. Storing arrays as field values allows you to model one-to-many or many-to-many relationships in a single document, instead of across separate collections as you might in a relational database.
ArrayList<String> stringArray = new ArrayList<String>(); BasicDBObject document = new BasicDBObject(); document. put("master", stringArray); db. getCollection("master"). insert(document);
To search the array of object in MongoDB, you can use $elemMatch operator. This operator allows us to search for more than one component from an array object.
I would definitely go with the first approach, storing the ObjectIds directly. This saves space, as ObjectId is 12 bytes whereas the second approach string is 24 bytes.
Also, if the ObjectIds are used to fetch the objects later, storing as ObjectId saves some hassle.
126
Unless you have a good reason not to, store them as an array of ObjectIds. It's more compact (12 bytes vs. 24) and it more accurately reflects what's stored. It can also enable driver-level support for following ObjectId references.
42
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
