# DSL: AshPostgres.DataLayer A postgres data layer that leverages Ecto's postgres capabilities. ## postgres Postgres data layer configuration ### Nested DSLs * [custom_indexes](#postgres-custom_indexes) * index * [custom_statements](#postgres-custom_statements) * statement * [manage_tenant](#postgres-manage_tenant) * [references](#postgres-references) * reference * [check_constraints](#postgres-check_constraints) * check_constraint ### Examples ``` postgres do repo MyApp.Repo table "organizations" end ``` ### Options

Name	Type	Default	Docs
repo *	module | (any, any -> any)		The repo that will be used to fetch your data. See the `AshPostgres.Repo` documentation for more. Can also be a function that takes a resource and a type `:read | :mutate` and returns the repo
migrate?	boolean	true	Whether or not to include this resource in the generated migrations with `mix ash.generate_migrations`
migration_types	Keyword.t	[]	A keyword list of attribute names to the ecto migration type that should be used for that attribute. Only necessary if you need to override the defaults.
migration_defaults	Keyword.t	[]	A keyword list of attribute names to the ecto migration default that should be used for that attribute. The string you use will be placed verbatim in the migration. Use fragments like `fragment(\\"now()\\")`, or for `nil`, use `\\"nil\\"`.
base_filter_sql	String.t		A raw sql version of the base_filter, e.g `representative = true`. Required if trying to create a unique constraint on a resource with a base_filter
simple_join_first_aggregates	list(atom)	[]	A list of `:first` type aggregate names that can be joined to using a simple join. Use when you have a `:first` aggregate that uses a to-many relationship , but your `filter` statement ensures that there is only one result. Optimizes the generated query.
skip_unique_indexes	atom | list(atom)	false	Skip generating unique indexes when generating migrations
unique_index_names	list({list(atom), String.t} | {list(atom), String.t, String.t})	[]	A list of unique index names that could raise errors that are not configured in identities, or an mfa to a function that takes a changeset and returns the list. In the format `{[:affected, :keys], "name_of_constraint"}` or `{[:affected, :keys], "name_of_constraint", "custom error message"}`
exclusion_constraint_names	`any`	[]	A list of exclusion constraint names that could raise errors. Must be in the format `{:affected_key, "name_of_constraint"}` or `{:affected_key, "name_of_constraint", "custom error message"}`
identity_index_names	`any`	[]	A keyword list of identity names to the unique index name that they should use when being managed by the migration generator.
foreign_key_names	list({atom | String.t, String.t} | {atom | String.t, String.t, String.t})	[]	A list of foreign keys that could raise errors, or an mfa to a function that takes a changeset and returns a list. In the format: `{:key, "name_of_constraint"}` or `{:key, "name_of_constraint", "custom error message"}`
migration_ignore_attributes	list(atom)	[]	A list of attributes that will be ignored when generating migrations.
table	String.t		The table to store and read the resource from. If this is changed, the migration generator will not remove the old table.
schema	String.t		The schema that the table is located in. Schema-based multitenancy will supercede this option. If this is changed, the migration generator will not remove the old schema.
polymorphic?	boolean	false	Declares this resource as polymorphic. See the [polymorphic resources guide](/documentation/topics/polymorphic_resources.md) for more.

## postgres.custom_indexes A section for configuring indexes to be created by the migration generator. In general, prefer to use `identities` for simple unique constraints. This is a tool to allow for declaring more complex indexes. ### Nested DSLs * [index](#postgres-custom_indexes-index) ### Examples ``` custom_indexes do index [:column1, :column2], unique: true, where: "thing = TRUE" end ``` ## postgres.custom_indexes.index ```elixir index fields ``` Add an index to be managed by the migration generator. ### Examples ``` index ["column", "column2"], unique: true, where: "thing = TRUE" ``` ### Arguments

Name	Type	Default	Docs
fields	atom | String.t | list(atom | String.t)		The fields to include in the index.

### Options

Name	Type	Default	Docs
name	String.t		the name of the index. Defaults to "#{table}_#{column}_index".
unique	boolean	false	indicates whether the index should be unique.
concurrently	boolean	false	indicates whether the index should be created/dropped concurrently.
using	String.t		configures the index type.
prefix	String.t		specify an optional prefix for the index.
where	String.t		specify conditions for a partial index.
message	String.t		A custom message to use for unique indexes that have been violated
include	list(String.t)		specify fields for a covering index. This is not supported by all databases. For more information on PostgreSQL support, please read the official docs.

### Introspection Target: `AshPostgres.CustomIndex` ## postgres.custom_statements A section for configuring custom statements to be added to migrations. Changing custom statements may require manual intervention, because Ash can't determine what order they should run in (i.e if they depend on table structure that you've added, or vice versa). As such, any `down` statements we run for custom statements happen first, and any `up` statements happen last. Additionally, when changing a custom statement, we must make some assumptions, i.e that we should migrate the old structure down using the previously configured `down` and recreate it. This may not be desired, and so what you may end up doing is simply modifying the old migration and deleting whatever was generated by the migration generator. As always: read your migrations after generating them! ### Nested DSLs * [statement](#postgres-custom_statements-statement) ### Examples ``` custom_statements do # the name is used to detect if you remove or modify the statement statement :pgweb_idx do up "CREATE INDEX pgweb_idx ON pgweb USING GIN (to_tsvector('english', title || ' ' || body));" down "DROP INDEX pgweb_idx;" end end ``` ## postgres.custom_statements.statement ```elixir statement name ``` Add a custom statement for migrations. ### Examples ``` statement :pgweb_idx do up "CREATE INDEX pgweb_idx ON pgweb USING GIN (to_tsvector('english', title || ' ' || body));" down "DROP INDEX pgweb_idx;" end ``` ### Arguments

Name	Type	Default	Docs
name *	atom		The name of the statement, must be unique within the resource

### Options

Name	Type	Default	Docs
up *	String.t		How to create the structure of the statement
down *	String.t		How to tear down the structure of the statement
code?	boolean	false	By default, we place the strings inside of ecto migration's `execute/1` function and assume they are sql. Use this option if you want to provide custom elixir code to be placed directly in the migrations

### Introspection Target: `AshPostgres.Statement` ## postgres.manage_tenant Configuration for the behavior of a resource that manages a tenant ### Examples ``` manage_tenant do template ["organization_", :id] create? true update? false end ``` ### Options

Name	Type	Default	Docs
template *	String.t | atom | list(String.t | atom)		A template that will cause the resource to create/manage the specified schema.
create?	boolean	true	Whether or not to automatically create a tenant when a record is created
update?	boolean	true	Whether or not to automatically update the tenant name if the record is udpated

## postgres.references A section for configuring the references (foreign keys) in resource migrations. This section is only relevant if you are using the migration generator with this resource. Otherwise, it has no effect. ### Nested DSLs * [reference](#postgres-references-reference) ### Examples ``` references do reference :post, on_delete: :delete, on_update: :update, name: "comments_to_posts_fkey" end ``` ### Options

Name	Type	Default	Docs
polymorphic_on_delete	:delete | :nilify | :nothing | :restrict		For polymorphic resources, configures the on_delete behavior of the automatically generated foreign keys to source tables.
polymorphic_on_update	:update | :nilify | :nothing | :restrict		For polymorphic resources, configures the on_update behavior of the automatically generated foreign keys to source tables.
polymorphic_name	:update | :nilify | :nothing | :restrict		For polymorphic resources, configures the on_update behavior of the automatically generated foreign keys to source tables.

## postgres.references.reference ```elixir reference relationship ``` Configures the reference for a relationship in resource migrations. Keep in mind that multiple relationships can theoretically involve the same destination and foreign keys. In those cases, you only need to configure the `reference` behavior for one of them. Any conflicts will result in an error, across this resource and any other resources that share a table with this one. For this reason, instead of adding a reference configuration for `:nothing`, its best to just leave the configuration out, as that is the default behavior if *no* relationship anywhere has configured the behavior of that reference. ### Examples ``` reference :post, on_delete: :delete, on_update: :update, name: "comments_to_posts_fkey" ``` ### Arguments

Name	Type	Default	Docs
relationship *	atom		The relationship to be configured

### Options

Name	Type	Default	Docs
ignore?	boolean		If set to true, no reference is created for the given relationship. This is useful if you need to define it in some custom way
on_delete	:delete | :nilify | :nothing | :restrict		What should happen to records of this resource when the referenced record of the *destination* resource is deleted.
on_update	:update | :nilify | :nothing | :restrict		What should happen to records of this resource when the referenced destination_attribute of the *destination* record is update.
deferrable	false | true | :initially	false	Wether or not the constraint is deferrable. This only affects the migration generator.
name	String.t		The name of the foreign key to generate in the database. Defaults to __fkey match_with Keyword.t Defines additional keys to the foreign key in order to build a composite foreign key. The key should be the name of the source attribute (in the current resource), the value the name of the destination attribute. match_type :simple | :partial | :full select if the match is `:simple`, `:partial`, or `:full` ### Introspection Target: `AshPostgres.Reference` ## postgres.check_constraints A section for configuring the check constraints for a given table. This can be used to automatically create those check constraints, or just to provide message when they are raised ### Nested DSLs * [check_constraint](#postgres-check_constraints-check_constraint) ### Examples ``` check_constraints do check_constraint :price, "price_must_be_positive", check: "price > 0", message: "price must be positive" end ``` ## postgres.check_constraints.check_constraint ```elixir check_constraint attribute, name ``` Add a check constraint to be validated. If a check constraint exists on the table but not in this section, and it produces an error, a runtime error will be raised. Provide a list of attributes instead of a single attribute to add the message to multiple attributes. By adding the `check` option, the migration generator will include it when generating migrations. ### Examples ``` check_constraint :price, "price_must_be_positive", check: "price > 0", message: "price must be positive" ``` ### Arguments Name Type Default Docs attribute * `any` The attribute or list of attributes to which an error will be added if the check constraint fails name * String.t The name of the constraint ### Options Name Type Default Docs message String.t The message to be added if the check constraint fails check String.t The contents of the check. If this is set, the migration generator will include it when generating migrations ### Introspection Target: `AshPostgres.CheckConstraint`