Error validating check constraint
Let's discuss some of this extra functionality.Changesets allow working with both kinds of data: Ecto changesets provide both validations and constraints which are ultimately turned into errors in case something goes wrong.
Let's imagine that those tags exist upfront and are all persisted to the database.Taking the initial example of users having addresses imagine those addresses are set up to belong to a country.If you want to allow users to bulk edit all addresses that belong to a single country, you can do so by changing the preload query: Optimistic locking works by keeping a "version" counter for each record; this counter gets incremented each time a modification is made to a record.For those reasons, changesets include the concept of empty values, which are values that will be automatically converted to the field's default value on See the documentation for those functions for more information.When using any of those APIs, you may run into situations where Ecto sees data is being replaced.Assuming we have a with the list of comments given, and correctly insert the new comment to the database.
Note, however, Ecto is doing a lot of work just to figure out something we knew since the beginning, which is that there is only one new comment.
For example, imagine a Post has many Comments where the comments have IDs 1, 2 and 3.
If you call option in particular must be used carefully as it would allow users to delete any associated data by simply not sending any data for a given field.
Imagine we get the data in this format: is a great fit.
It will automatically remove any tag not given and properly associate all of the given tags with the post.
By moving constraints to the database, we also provide a safe, correct and data-race free means of checking the user input.