improvement: don't sort identity keys.

There are important implications here, specifically that there are
optimizations that can be had based on what the first column in a
unique constraint is, and we want to make sure that can be taken advantage of.

closes #313

Author: zachdaniel

lib/migration_generator/migration_generator.ex

@@ -557,7 +557,7 @@ defmodule AshPostgres.MigrationGenerator do
           |> Kernel.!()
         end)
         |> Enum.uniq_by(fn identity ->
-          {Enum.sort(identity.keys), identity.base_filter}
+          {identity.keys, identity.base_filter}
         end)
 
       new_snapshot = %{new_snapshot | identities: all_identities}
@@ -740,7 +740,7 @@ defmodule AshPostgres.MigrationGenerator do
 
         identities =
           Enum.reject(identities, fn identity ->
-            Enum.sort(identity.keys) == primary_key
+            identity.keys == primary_key
           end)
 
         {primary_key, identities}
@@ -1817,7 +1817,7 @@ defmodule AshPostgres.MigrationGenerator do
         Enum.reject(old_snapshot.identities, fn old_identity ->
           Enum.find(snapshot.identities, fn identity ->
             identity.name == old_identity.name &&
-              Enum.sort(old_identity.keys) == Enum.sort(identity.keys) &&
+              old_identity.keys == identity.keys &&
               old_identity.base_filter == identity.base_filter &&
               old_identity.all_tenants? == identity.all_tenants? &&
               old_identity.nils_distinct? == identity.nils_distinct? &&
@@ -1874,7 +1874,7 @@ defmodule AshPostgres.MigrationGenerator do
           if identity.all_tenants? do
             Enum.find(old_snapshot.identities, fn old_identity ->
               old_identity.name == identity.name &&
-                Enum.sort(old_identity.keys) == Enum.sort(identity.keys) &&
+                old_identity.keys == identity.keys &&
                 old_identity.base_filter == identity.base_filter &&
                 old_identity.all_tenants? == identity.all_tenants? &&
                 old_identity.nils_distinct? == identity.nils_distinct? &&
@@ -1888,7 +1888,7 @@ defmodule AshPostgres.MigrationGenerator do
         Enum.reject(snapshot.identities, fn identity ->
           Enum.find(old_snapshot.identities, fn old_identity ->
             old_identity.name == identity.name &&
-              Enum.sort(old_identity.keys) == Enum.sort(identity.keys) &&
+              old_identity.keys == identity.keys &&
               old_identity.base_filter == identity.base_filter &&
               old_identity.all_tenants? == identity.all_tenants? &&
               old_identity.nils_distinct? == identity.nils_distinct? &&
@@ -3244,9 +3244,6 @@ defmodule AshPostgres.MigrationGenerator do
   defp load_identity(identity, table) do
     identity
     |> Map.update!(:name, &maybe_to_atom/1)
-    |> Map.update!(:keys, fn keys ->
-      Enum.sort(keys)
-    end)
     |> add_index_name(table)
     |> Map.put_new(:base_filter, nil)
     |> Map.put_new(:all_tenants?, false)

priv/resource_snapshots/test_repo/post_links/20240610195853.json

@@ -0,0 +1,100 @@
+{
+  "attributes": [
+    {
+      "default": "\"active\"",
+      "size": null,
+      "type": "text",
+      "source": "state",
+      "references": null,
+      "primary_key?": false,
+      "allow_nil?": true,
+      "generated?": false
+    },
+    {
+      "default": "nil",
+      "size": null,
+      "type": "uuid",
+      "source": "source_post_id",
+      "references": {
+        "name": "post_links_source_post_id_fkey",
+        "table": "posts",
+        "multitenancy": {
+          "global": null,
+          "strategy": null,
+          "attribute": null
+        },
+        "primary_key?": true,
+        "destination_attribute": "id",
+        "schema": "public",
+        "deferrable": false,
+        "index?": false,
+        "destination_attribute_default": null,
+        "destination_attribute_generated": null,
+        "on_delete": null,
+        "on_update": null,
+        "match_with": null,
+        "match_type": null
+      },
+      "primary_key?": true,
+      "allow_nil?": false,
+      "generated?": false
+    },
+    {
+      "default": "nil",
+      "size": null,
+      "type": "uuid",
+      "source": "destination_post_id",
+      "references": {
+        "name": "post_links_destination_post_id_fkey",
+        "table": "posts",
+        "multitenancy": {
+          "global": null,
+          "strategy": null,
+          "attribute": null
+        },
+        "primary_key?": true,
+        "destination_attribute": "id",
+        "schema": "public",
+        "deferrable": false,
+        "index?": false,
+        "destination_attribute_default": null,
+        "destination_attribute_generated": null,
+        "on_delete": null,
+        "on_update": null,
+        "match_with": null,
+        "match_type": null
+      },
+      "primary_key?": true,
+      "allow_nil?": false,
+      "generated?": false
+    }
+  ],
+  "table": "post_links",
+  "hash": "AF3FA145E25BB98CD83D51B551C8E623F1CE088DA1DE09B9905CA5E4B085C872",
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "multitenancy": {
+    "global": null,
+    "strategy": null,
+    "attribute": null
+  },
+  "schema": null,
+  "identities": [
+    {
+      "name": "unique_link",
+      "keys": [
+        "destination_post_id",
+        "source_post_id"
+      ],
+      "where": null,
+      "base_filter": null,
+      "all_tenants?": false,
+      "nils_distinct?": true,
+      "index_name": "post_links_unique_link_index"
+    }
+  ],
+  "has_create_action": true,
+  "custom_indexes": [],
+  "custom_statements": [],
+  "base_filter": null,
+  "check_constraints": []
+}

priv/test_repo/migrations/20240610195853_migrate_resources27.exs

@@ -0,0 +1,37 @@
+defmodule AshPostgres.TestRepo.Migrations.MigrateResources27 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
+    drop_if_exists(
+      unique_index(:post_links, ["source_post_id", "destination_post_id"],
+        name: "post_links_unique_link_index"
+      )
+    )
+
+    create(
+      unique_index(:post_links, ["destination_post_id", "source_post_id"],
+        name: "post_links_unique_link_index"
+      )
+    )
+  end
+
+  def down do
+    drop_if_exists(
+      unique_index(:post_links, ["destination_post_id", "source_post_id"],
+        name: "post_links_unique_link_index"
+      )
+    )
+
+    create(
+      unique_index(:post_links, ["source_post_id", "destination_post_id"],
+        name: "post_links_unique_link_index"
+      )
+    )
+  end
+end