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The Ecto documentation describes the options available to references/2, but does not document what those options do. The options available are:
:nothing:delete_all:nilify_all:restrictWhat do they do?
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Migration behaviour (Ecto SQL v3. 8.3) Migrations are used to modify your database schema over time. This module provides many helpers for migrating the database, allowing developers to use Elixir to alter their storage in a way that is database independent.
Ecto is an official Elixir project providing a database wrapper and integrated query language. With Ecto we're able to create migrations, define schemas, insert and update records, and query them. Changesets. In order to insert, update or delete data from the database, Ecto. Repo.
This is actually a SQL question at root.
https://github.com/elixir-ecto/ecto_sql/blob/52f9d27a7ad86442f442bad2f7ebd19ba09ddc61/lib/ecto/adapters/myxql/connection.ex#L902-L905
The PostgreSQL documentation outlines these options clearly:
:nothing - if any referencing rows still exist when the constraint is checked, an error is raised; this is the default behavior if you do not specify anything.:delete_all - specifies that when a referenced row is deleted, row(s) referencing it should be automatically deleted as well:nilify_all - causes the referencing column(s) in the referencing row(s) to be set to nil when the referenced row is deleted:restrict - prevents deletion of a referenced row. It will fail if there is a referenced object.:nothing and :restrict are similar but:
the essential difference between these two choices is that [
:nothing] allows the check to be deferred until later in the transaction, whereas [:restrict] does not.
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