feat: add check_constraints, both for validation and migrations

.formatter.exs

@@ -2,8 +2,12 @@
 # DONT MODIFY IT BY HAND
 locals_without_parens = [
   base_filter_sql: 1,
+  check: 1,
+  check_constraint: 2,
+  check_constraint: 3,
   create?: 1,
   foreign_key_names: 1,
+  message: 1,
   migrate?: 1,
   name: 1,
   on_delete: 1,

lib/ash_postgres.ex

@@ -24,6 +24,11 @@ defmodule AshPostgres do
     Extension.get_entities(resource, [:postgres, :references])
   end
 
+  @doc "The configured check_constraints for a resource"
+  def check_constraints(resource) do
+    Extension.get_entities(resource, [:postgres, :check_constraints])
+  end
+
   @doc "The configured polymorphic_reference_on_delete for a resource"
   def polymorphic_on_delete(resource) do
     Extension.get_opt(resource, [:postgres, :references], :polymorphic_on_delete, nil, true)

lib/check_constraint.ex

@@ -0,0 +1,31 @@
+defmodule AshPostgres.CheckConstraint do
+  @moduledoc """
+  Contains configuration for database check constraints
+  """
+  defstruct [:attribute, :name, :message, :check]
+
+  def schema do
+    [
+      attribute: [
+        type: :any,
+        doc:
+          "The attribute or list of attributes to which an error will be added if the check constraint fails",
+        required: true
+      ],
+      name: [
+        type: :string,
+        required: true,
+        doc: "The name of the constraint"
+      ],
+      message: [
+        type: :string,
+        doc: "The message to be added if the check constraint fails"
+      ],
+      check: [
+        type: :string,
+        doc:
+          "The contents of the check. If this is set, the migration generator will include it when generating migrations"
+      ]
+    ]
+  end
+end

lib/data_layer.ex

@@ -96,6 +96,79 @@ defmodule AshPostgres.DataLayer do
     ]
   }
 
+  @check_constraint %Ash.Dsl.Entity{
+    name: :check_constraint,
+    describe: """
+    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"
+      """
+    ],
+    args: [:attribute, :name],
+    target: AshPostgres.CheckConstraint,
+    schema: AshPostgres.CheckConstraint.schema()
+  }
+
+  @check_constraints %Ash.Dsl.Section{
+    name: :check_constraints,
+    describe: """
+    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
+    """,
+    examples: [
+      """
+      check_constraints do
+        check_constraint :price, "price_must_be_positive", check: "price > 0", message: "price must be positive"
+      end
+      """
+    ],
+    entities: [@check_constraint]
+  }
+
+  @references %Ash.Dsl.Section{
+    name: :references,
+    describe: """
+    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.
+    """,
+    examples: [
+      """
+      references do
+        reference :post, on_delete: :delete, on_update: :update, name: "comments_to_posts_fkey"
+      end
+      """
+    ],
+    entities: [@reference],
+    schema: [
+      polymorphic_on_delete: [
+        type: {:one_of, [:delete, :nilify, :nothing, :restrict]},
+        doc:
+          "For polymorphic resources, configures the on_delete behavior of the automatically generated foreign keys to source tables."
+      ],
+      polymorphic_on_update: [
+        type: {:one_of, [:update, :nilify, :nothing, :restrict]},
+        doc:
+          "For polymorphic resources, configures the on_update behavior of the automatically generated foreign keys to source tables."
+      ],
+      polymorphic_name: [
+        type: {:one_of, [:update, :nilify, :nothing, :restrict]},
+        doc:
+          "For polymorphic resources, configures the on_update behavior of the automatically generated foreign keys to source tables."
+      ]
+    ]
+  }
+
   @postgres %Ash.Dsl.Section{
     name: :postgres,
     describe: """
@@ -103,7 +176,8 @@ defmodule AshPostgres.DataLayer do
     """,
     sections: [
       @manage_tenant,
-      @references
+      @references,
+      @check_constraints
     ],
     modules: [
       :repo
@@ -548,26 +622,23 @@ defmodule AshPostgres.DataLayer do
       record
       |> set_table(changeset, type)
       |> Ecto.Changeset.change(changeset.attributes)
+      |> add_configured_foreign_key_constraints(record.__struct__)
+      |> add_unique_indexes(record.__struct__, changeset.tenant, changeset)
+      |> add_check_constraints(record.__struct__)
 
     case type do
       :create ->
         ecto_changeset
-        |> add_unique_indexes(record.__struct__, changeset.tenant, changeset)
         |> add_my_foreign_key_constraints(record.__struct__)
-        |> add_configured_foreign_key_constraints(record.__struct__)
 
       type when type in [:upsert, :update] ->
         ecto_changeset
-        |> add_unique_indexes(record.__struct__, changeset.tenant, changeset)
         |> add_my_foreign_key_constraints(record.__struct__)
         |> add_related_foreign_key_constraints(record.__struct__)
-        |> add_configured_foreign_key_constraints(record.__struct__)
 
       :delete ->
         ecto_changeset
-        |> add_unique_indexes(record.__struct__, changeset.tenant, changeset)
         |> add_related_foreign_key_constraints(record.__struct__)
-        |> add_configured_foreign_key_constraints(record.__struct__)
     end
   end
 
@@ -585,6 +656,21 @@ defmodule AshPostgres.DataLayer do
     end
   end
 
+  defp add_check_constraints(changeset, resource) do
+    resource
+    |> AshPostgres.check_constraints()
+    |> Enum.reduce(changeset, fn constraint, changeset ->
+      constraint.attribute
+      |> List.wrap()
+      |> Enum.reduce(changeset, fn attribute, changeset ->
+        Ecto.Changeset.check_constraint(changeset, attribute,
+          name: constraint.name,
+          message: constraint.message || "is invalid"
+        )
+      end)
+    end)
+  end
+
   defp add_related_foreign_key_constraints(changeset, resource) do
     # TODO: this doesn't guarantee us to get all of them, because if something is related to this
     # schema and there is no back-relation, then this won't catch it's foreign key constraints

lib/migration_generator/migration_generator.ex

@@ -841,9 +841,26 @@ defmodule AshPostgres.MigrationGenerator do
     name in keys || (multitenancy.attribute && name == multitenancy.attribute)
   end
 
+  defp after?(
+         %Operation.AddCheckConstraint{
+           constraint: %{attribute: attribute_or_attributes},
+           table: table,
+           multitenancy: multitenancy
+         },
+         %Operation.AddAttribute{table: table, attribute: %{name: name}}
+       ) do
+    name in List.wrap(attribute_or_attributes) ||
+      (multitenancy.attribute && multitenancy.attribute in List.wrap(attribute_or_attributes))
+  end
+
   defp after?(%Operation.AddUniqueIndex{table: table}, %Operation.RemoveUniqueIndex{table: table}),
     do: true
 
+  defp after?(%Operation.AddCheckConstraint{table: table}, %Operation.RemoveCheckConstraint{
+         table: table
+       }),
+       do: true
+
   defp after?(
          %Operation.AddUniqueIndex{identity: %{keys: keys}, table: table},
          %Operation.AlterAttribute{table: table, new_attribute: %{name: name}}
@@ -858,6 +875,26 @@ defmodule AshPostgres.MigrationGenerator do
     name in keys
   end
 
+  defp after?(
+         %Operation.AddCheckConstraint{
+           constraint: %{attribute: attribute_or_attributes},
+           table: table
+         },
+         %Operation.AlterAttribute{table: table, new_attribute: %{name: name}}
+       ) do
+    name in List.wrap(attribute_or_attributes)
+  end
+
+  defp after?(
+         %Operation.AddCheckConstraint{
+           constraint: %{attribute: attribute_or_attributes},
+           table: table
+         },
+         %Operation.RenameAttribute{table: table, new_attribute: %{name: name}}
+       ) do
+    name in List.wrap(attribute_or_attributes)
+  end
+
   defp after?(
          %Operation.RemoveUniqueIndex{identity: %{keys: keys}, table: table},
          %Operation.RemoveAttribute{table: table, attribute: %{name: name}}
@@ -872,6 +909,20 @@ defmodule AshPostgres.MigrationGenerator do
     name in keys
   end
 
+  defp after?(
+         %Operation.RemoveCheckConstraint{constraint: %{attribute: attributes}, table: table},
+         %Operation.RemoveAttribute{table: table, attribute: %{name: name}}
+       ) do
+    name in List.wrap(attributes)
+  end
+
+  defp after?(
+         %Operation.RemoveCheckConstraint{constraint: %{attribute: attributes}, table: table},
+         %Operation.RenameAttribute{table: table, old_attribute: %{name: name}}
+       ) do
+    name in List.wrap(attributes)
+  end
+
   defp after?(%Operation.AlterAttribute{table: table}, %Operation.DropForeignKey{
          table: table,
          direction: :up
@@ -960,6 +1011,10 @@ defmodule AshPostgres.MigrationGenerator do
     true
   end
 
+  defp after?(%Operation.AddCheckConstraint{table: table}, %Operation.CreateTable{table: table}) do
+    true
+  end
+
   defp after?(%Operation.AlterAttribute{new_attribute: %{references: references}}, _)
        when not is_nil(references),
        do: true
@@ -982,6 +1037,7 @@ defmodule AshPostgres.MigrationGenerator do
     empty_snapshot = %{
       attributes: [],
       identities: [],
+      check_constraints: [],
       table: snapshot.table,
       repo: snapshot.repo,
       multitenancy: %{
@@ -1039,7 +1095,42 @@ defmodule AshPostgres.MigrationGenerator do
         }
       end)
 
-    [unique_indexes_to_remove, attribute_operations, unique_indexes_to_add, acc]
+    constraints_to_add =
+      snapshot.check_constraints
+      |> Enum.reject(fn constraint ->
+        Enum.find(old_snapshot.check_constraints, fn old_constraint ->
+          old_constraint.check == constraint.check && old_constraint.name == constraint.name
+        end)
+      end)
+      |> Enum.map(fn constraint ->
+        %Operation.AddCheckConstraint{
+          constraint: constraint,
+          table: snapshot.table
+        }
+      end)
+
+    constraints_to_remove =
+      old_snapshot.check_constraints
+      |> Enum.reject(fn old_constraint ->
+        Enum.find(snapshot.check_constraints, fn constraint ->
+          old_constraint.check == constraint.check && old_constraint.name == constraint.name
+        end)
+      end)
+      |> Enum.map(fn old_constraint ->
+        %Operation.RemoveCheckConstraint{
+          constraint: old_constraint,
+          table: old_snapshot.table
+        }
+      end)
+
+    [
+      unique_indexes_to_remove,
+      attribute_operations,
+      unique_indexes_to_add,
+      constraints_to_add,
+      constraints_to_remove,
+      acc
+    ]
     |> Enum.concat()
     |> Enum.map(&Map.put(&1, :multitenancy, snapshot.multitenancy))
     |> Enum.map(&Map.put(&1, :old_multitenancy, old_snapshot.multitenancy))
@@ -1338,6 +1429,7 @@ defmodule AshPostgres.MigrationGenerator do
       attributes: attributes(resource),
       identities: identities(resource),
       table: table || AshPostgres.table(resource),
+      check_constraints: check_constraints(resource),
       repo: AshPostgres.repo(resource),
       multitenancy: multitenancy(resource),
       base_filter: AshPostgres.base_filter_sql(resource),
@@ -1358,6 +1450,37 @@ defmodule AshPostgres.MigrationGenerator do
     |> Enum.any?(&(&1.type == :create))
   end
 
+  defp check_constraints(resource) do
+    resource
+    |> AshPostgres.check_constraints()
+    |> Enum.filter(& &1.check)
+    |> case do
+      [] ->
+        []
+
+      constraints ->
+        base_filter = Ash.Resource.Info.base_filter(resource)
+
+        if base_filter && !AshPostgres.base_filter_sql(resource) do
+          raise """
+          Cannot create a check constraint for a resource with a base filter without also configuring `base_filter_sql`.
+
+          You must provide the `base_filter_sql` option, or manually create add the check constraint to your migrations.
+          """
+        end
+
+        constraints
+    end
+    |> Enum.map(fn constraint ->
+      %{
+        name: constraint.name,
+        attribute: List.wrap(constraint.attribute),
+        check: constraint.check,
+        base_filter: AshPostgres.base_filter_sql(resource)
+      }
+    end)
+  end
+
   defp multitenancy(resource) do
     strategy = Ash.Resource.Info.multitenancy_strategy(resource)
     attribute = Ash.Resource.Info.multitenancy_attribute(resource)
@@ -1452,7 +1575,9 @@ defmodule AshPostgres.MigrationGenerator do
 
         if base_filter && !AshPostgres.base_filter_sql(resource) do
           raise """
-          Currently, ash_postgres cannot translate your base_filter #{inspect(base_filter)} into sql. You must provide the `base_filter_sql` option, or skip unique indexes with `skip_unique_indexes`"
+          Cannot create a unique index for a resource with a base filter without also configuring `base_filter_sql`.
+
+          You must provide the `base_filter_sql` option, or skip unique indexes with `skip_unique_indexes`"
           """
         end
 
@@ -1533,6 +1658,8 @@ defmodule AshPostgres.MigrationGenerator do
     |> Map.update!(:attributes, fn attributes ->
       Enum.map(attributes, &load_attribute(&1, snapshot.table))
     end)
+    |> Map.put_new(:check_constraints, [])
+    |> Map.update!(:check_constraints, &load_check_constraints/1)
     |> Map.update!(:repo, &String.to_atom/1)
     |> Map.put_new(:multitenancy, %{
       attribute: nil,
@@ -1542,6 +1669,16 @@ defmodule AshPostgres.MigrationGenerator do
     |> Map.update!(:multitenancy, &load_multitenancy/1)
   end
 
+  defp load_check_constraints(constraints) do
+    Enum.map(constraints, fn constraint ->
+      Map.update!(constraint, :attribute, fn attribute ->
+        attribute
+        |> List.wrap()
+        |> Enum.map(&String.to_atom/1)
+      end)
+    end)
+  end
+
   defp load_multitenancy(multitenancy) do
     multitenancy
     |> Map.update!(:strategy, fn strategy -> strategy && String.to_atom(strategy) end)

lib/migration_generator/operation.ex

@@ -546,4 +546,55 @@ defmodule AshPostgres.MigrationGenerator.Operation do
       end
     end
   end
+
+  defmodule AddCheckConstraint do
+    @moduledoc false
+    defstruct [:table, :constraint, :multitenancy, :old_multitenancy, no_phase: true]
+
+    def up(%{
+          constraint: %{
+            name: name,
+            check: check,
+            base_filter: base_filter
+          },
+          table: table
+        }) do
+      if base_filter do
+        "create constraint(:#{table}, :#{name}, check: \"#{base_filter} AND #{check}\")"
+      else
+        "create constraint(:#{table}, :#{name}, check: \"#{check}\")"
+      end
+    end
+
+    def down(%{
+          constraint: %{name: name},
+          table: table
+        }) do
+      "drop_if_exists constraint(:#{table}, :#{name})"
+    end
+  end
+
+  defmodule RemoveCheckConstraint do
+    @moduledoc false
+    defstruct [:table, :constraint, :multitenancy, :old_multitenancy, no_phase: true]
+
+    def up(%{constraint: %{name: name}, table: table}) do
+      "drop_if_exists constraint(:#{table}, :#{name})"
+    end
+
+    def down(%{
+          constraint: %{
+            name: name,
+            check: check,
+            base_filter: base_filter
+          },
+          table: table
+        }) do
+      if base_filter do
+        "create constraint(:#{table}, :#{name}, check: \"#{base_filter} AND #{check}\")"
+      else
+        "create constraint(:#{table}, :#{name}, check: \"#{check}\")"
+      end
+    end
+  end
 end

priv/resource_snapshots/test_repo/comment_ratings/20210419181749.json

@@ -0,0 +1,54 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"uuid_generate_v4()\")",
+      "generated?": false,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "resource_id",
+      "primary_key?": false,
+      "references": {
+        "destination_field": "id",
+        "multitenancy": {
+          "attribute": null,
+          "global": null,
+          "strategy": null
+        },
+        "name": "comment_ratings_id_fkey",
+        "on_delete": null,
+        "on_update": null,
+        "table": "comments"
+      },
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "score",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "has_create_action": true,
+  "hash": "38D98E7F5B0891597BF0D1A1632638954CB7721E01310F989A41D1379E470DF8",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "comment_ratings"
+}

priv/resource_snapshots/test_repo/comments/20210419181749.json

@@ -0,0 +1,63 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"uuid_generate_v4()\")",
+      "generated?": false,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "likes",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "post_id",
+      "primary_key?": false,
+      "references": {
+        "destination_field": "id",
+        "multitenancy": {
+          "attribute": null,
+          "global": null,
+          "strategy": null
+        },
+        "name": "special_name_fkey",
+        "on_delete": "delete",
+        "on_update": "update",
+        "table": "posts"
+      },
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "title",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "has_create_action": true,
+  "hash": "AC27C8DBB84D6687136A96A5E1393042E31235B847365E5DB26DE57F5FC55604",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "comments"
+}

priv/resource_snapshots/test_repo/integer_posts/20210419181749.json

@@ -0,0 +1,34 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "nil",
+      "generated?": true,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "title",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "has_create_action": true,
+  "hash": "38D842CAAC012D0973D6A661E8EF0C429BDB535E3AB78EC4F24C951ED323FEFE",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "integer_posts"
+}

priv/resource_snapshots/test_repo/post_ratings/20210419181749.json

@@ -0,0 +1,54 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"uuid_generate_v4()\")",
+      "generated?": false,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "resource_id",
+      "primary_key?": false,
+      "references": {
+        "destination_field": "id",
+        "multitenancy": {
+          "attribute": null,
+          "global": null,
+          "strategy": null
+        },
+        "name": "post_ratings_id_fkey",
+        "on_delete": null,
+        "on_update": null,
+        "table": "posts"
+      },
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "score",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "has_create_action": true,
+  "hash": "04586179DB8456574D279F2B6BE7AAEAC78D41E556572970B373607084782402",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "post_ratings"
+}

priv/resource_snapshots/test_repo/posts/20210419181749.json

@@ -0,0 +1,88 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "category",
+      "primary_key?": false,
+      "references": null,
+      "type": "citext"
+    },
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"uuid_generate_v4()\")",
+      "generated?": false,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "price",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "public",
+      "primary_key?": false,
+      "references": null,
+      "type": "boolean"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "score",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "title",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    },
+    {
+      "allow_nil?": true,
+      "default": "\"sponsored\"",
+      "generated?": false,
+      "name": "type",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    }
+  ],
+  "base_filter": "type = 'sponsored'",
+  "check_constraints": [
+    {
+      "attribute": [
+        "price"
+      ],
+      "base_filter": "type = 'sponsored'",
+      "check": "price > 0",
+      "name": "price_must_be_positive"
+    }
+  ],
+  "has_create_action": true,
+  "hash": "AF0084C380DBCD40FCCB82B49E7B36299087EBC0F46E2664524F47C0757D8EB6",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "posts"
+}

priv/test_repo/migrations/20210419181749_migrate_resources7.exs

@@ -0,0 +1,59 @@
+defmodule AshPostgres.TestRepo.Migrations.MigrateResources7 do
+  @moduledoc """
+  Updates resources based on their most recent snapshots.
+
+  This file was autogenerated with `mix ash_postgres.generate_migrations`
+  """
+
+  use Ecto.Migration
+
+  def up do
+    alter table(:posts) do
+      modify :score, :bigint
+      add :price, :bigint
+    end
+
+    create constraint(:posts, :price_must_be_positive, check: "type = 'sponsored' AND price > 0")
+
+    alter table(:post_ratings) do
+      modify :score, :bigint
+    end
+
+    alter table(:integer_posts) do
+      modify :id, :bigint
+    end
+
+    alter table(:comments) do
+      modify :likes, :bigint
+    end
+
+    alter table(:comment_ratings) do
+      modify :score, :bigint
+    end
+  end
+
+  def down do
+    alter table(:comment_ratings) do
+      modify :score, :integer
+    end
+
+    alter table(:comments) do
+      modify :likes, :integer
+    end
+
+    alter table(:integer_posts) do
+      modify :id, :integer
+    end
+
+    alter table(:post_ratings) do
+      modify :score, :integer
+    end
+
+    drop_if_exists constraint(:posts, :price_must_be_positive)
+
+    alter table(:posts) do
+      remove :price
+      modify :score, :integer
+    end
+  end
+end

test/constraint_test.exs

@@ -0,0 +1,15 @@
+defmodule AshPostgres.ConstraintTest do
+  @moduledoc false
+  use AshPostgres.RepoCase, async: false
+  alias AshPostgres.Test.{Api, Post}
+
+  require Ash.Query
+
+  test "constraint messages are properly raised" do
+    assert_raise Ash.Error.Invalid, ~r/yo, bad price/, fn ->
+      Post
+      |> Ash.Changeset.new(%{title: "title", price: -1})
+      |> Api.create!()
+    end
+  end
+end

test/migration_generator_test.exs

@@ -559,6 +559,95 @@ defmodule AshPostgres.MigrationGeneratorTest do
     end
   end
 
+  describe "check constraints" do
+    setup do
+      on_exit(fn ->
+        File.rm_rf!("test_snapshots_path")
+        File.rm_rf!("test_migration_path")
+      end)
+    end
+
+    test "when added, the constraint is created" do
+      defposts do
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:price, :integer)
+        end
+
+        postgres do
+          check_constraints do
+            check_constraint(:price, "price_must_be_positive", check: "price > 0")
+          end
+        end
+      end
+
+      defapi([Post])
+
+      AshPostgres.MigrationGenerator.generate(Api,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false
+      )
+
+      assert file =
+               "test_migration_path/**/*_migrate_resources*.exs"
+               |> Path.wildcard()
+               |> Enum.sort()
+               |> Enum.at(0)
+
+      assert File.read!(file) =~
+               ~S[create constraint(:posts, :price_must_be_positive, check: "price > 0")]
+    end
+
+    test "when removed, the constraint is dropped before modification" do
+      defposts do
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:price, :integer)
+        end
+
+        postgres do
+          check_constraints do
+            check_constraint(:price, "price_must_be_positive", check: "price > 0")
+          end
+        end
+      end
+
+      defapi([Post])
+
+      AshPostgres.MigrationGenerator.generate(Api,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false
+      )
+
+      defposts do
+        attributes do
+          uuid_primary_key(:id)
+          attribute(:price, :integer)
+        end
+      end
+
+      AshPostgres.MigrationGenerator.generate(Api,
+        snapshot_path: "test_snapshots_path",
+        migration_path: "test_migration_path",
+        quiet: true,
+        format: false
+      )
+
+      assert file =
+               "test_migration_path/**/*_migrate_resources*.exs"
+               |> Path.wildcard()
+               |> Enum.sort()
+               |> Enum.at(1)
+
+      assert File.read!(file) =~
+               ~S[drop_if_exists constraint(:posts, :price_must_be_positive)]
+    end
+  end
+
   describe "polymorphic resources" do
     setup do
       on_exit(fn ->

test/support/resources/post.ex

@@ -6,6 +6,14 @@ defmodule AshPostgres.Test.Post do
   postgres do
     table "posts"
     repo AshPostgres.TestRepo
+    base_filter_sql "type = 'sponsored'"
+
+    check_constraints do
+      check_constraint(:price, "price_must_be_positive",
+        message: "yo, bad price",
+        check: "price > 0"
+      )
+    end
   end
 
   resource do
@@ -35,6 +43,7 @@ defmodule AshPostgres.Test.Post do
     attribute(:public, :boolean)
     attribute(:category, :ci_string)
     attribute(:type, :atom, default: :sponsored, private?: true, writable?: false)
+    attribute(:price, :integer)
   end
 
   relationships do