Error updating group repository metadata input contained no data to chat dating
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.
If you need deletion, it is often preferred to add a separate boolean virtual field to the changeset function that will allow you to manually mark it for deletion, as in the example below: This means that when working with changesets that are not meant to be persisted to the database, such as schemaless changesets, you may need to explicitly set the action to one specific value.
Frameworks such as Phoenix use the action value to define how HTML forms should act.
The changeset would have the following errors: In this case, we haven't checked the unique constraint in the e-mail field because the data did not validate.
Let's fix the age and the name, and assume that the e-mail already exists in the database: Validations and constraints define an explicit boundary when the check happens.
Many times, the data given on cast needs to be further pruned, specially regarding empty values.
For example, if you are gathering data to be cast from the command line or through an HTML form or any other text-based format, it is likely those means cannot express nil values.
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.
The difference between them is that most validations can be executed without a need to interact with the database and, therefore, are always executed before attempting to insert or update the entry in the database.