Mastering MongoDB 4.x - Second Edition

collMod

collMod is used to pass flags to a collection by modifying the underlying database's behavior.

Since version 3.2, the most interesting set of flags that we can pass to a collection is document validation.

Document validation can specify a set of rules to be applied to new updates and inserts into a collection. This means that current documents will be checked if they get modified.

We can only apply validations to documents that are already valid if we set validationLevel to moderate. By specifying validationAction, we can log documents that are invalid by setting it to warn or prevent updates from happening altogether by setting it to error.

For example, with the previous example of bookOrders we can set validator on the isbn and ...