docs: add global_secondary_index to DSL reference and getting started guide

documentation/dsls/DSL-AshDynamo.DataLayer.md

@@ -15,6 +15,11 @@ dynamodb do
   table "users"
   partition_key :email
   sort_key :inserted_at
+
+  global_secondary_index :by_status do
+    partition_key :status
+    sort_key :inserted_at
+  end
 end
 ```
 
@@ -25,3 +30,24 @@ end
 | [`table`](#dynamodb-table){: #dynamodb-table }                         | `String.t` |         | Table name to read from/write to. Defaults to the underscored resource name. |
 | [`partition_key`](#dynamodb-partition_key){: #dynamodb-partition_key } | `atom`     |         | Required partition (hash) key attribute name.                                |
 | [`sort_key`](#dynamodb-sort_key){: #dynamodb-sort_key }                | `atom`     | `nil`   | Optional sort (range) key attribute name.                                    |
+
+### dynamodb.global_secondary_index
+
+Defines a Global Secondary Index (GSI) for automatic query routing.
+
+When a query filters on a GSI's partition key, AshDynamo automatically routes the query to that index instead of scanning the table.
+
+```elixir
+global_secondary_index :by_status do
+  partition_key :status
+  sort_key :inserted_at
+end
+```
+
+#### Options
+
+| Name                                                                                                                 | Type   | Default | Docs                                                     |
+| -------------------------------------------------------------------------------------------------------------------- | ------ | ------- | -------------------------------------------------------- |
+| [`name`](#dynamodb-global_secondary_index-name){: #dynamodb-global_secondary_index-name }                            | `atom` |         | Index name (used as the DynamoDB `IndexName` parameter). |
+| [`partition_key`](#dynamodb-global_secondary_index-partition_key){: #dynamodb-global_secondary_index-partition_key } | `atom` |         | Partition (hash) key attribute for this GSI.             |
+| [`sort_key`](#dynamodb-global_secondary_index-sort_key){: #dynamodb-global_secondary_index-sort_key }                | `atom` | `nil`   | Optional sort (range) key attribute for this GSI.        |

documentation/tutorials/getting-started-with-ash-dynamo.md

@@ -14,6 +14,11 @@ defmodule MyApp.Post do
     table "posts"
     partition_key :id
     sort_key :inserted_at
+
+    global_secondary_index :by_status do
+      partition_key :status
+      sort_key :inserted_at
+    end
   end
 
   actions do

lib/ash_dynamo/data_layer/secondary_index.ex

@@ -8,10 +8,16 @@ defmodule AshDynamo.DataLayer.SecondaryIndex do
   The `:type` field is auto-set by the entity definition:
   - `:global` for Global Secondary Indexes
   - `:local` for Local Secondary Indexes
-
-  Projection is always `ALL` — every index includes all table attributes.
   """
 
+  @type t :: %__MODULE__{
+          name: atom(),
+          type: :global | :local,
+          partition_key: atom(),
+          sort_key: atom() | nil,
+          __spark_metadata__: map() | nil
+        }
+
   defstruct [
     :name,
     :type,

mix.lock

@@ -1,5 +1,5 @@
 %{
-  "ash": {:hex, :ash, "3.15.0", "e52c6be244bb22f4afc5eb9fe9cc6e8f034906ef43c114f75c3c372ba6b470c6", [:mix], [{:crux, ">= 0.1.2 and < 1.0.0-0", [hex: :crux, repo: "hexpm", optional: false]}, {:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:ecto, "~> 3.7", [hex: :ecto, repo: "hexpm", optional: false]}, {:ets, "~> 0.8", [hex: :ets, repo: "hexpm", optional: false]}, {:igniter, ">= 0.6.29 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, ">= 1.0.0", [hex: :jason, repo: "hexpm", optional: false]}, {:picosat_elixir, "~> 0.2", [hex: :picosat_elixir, repo: "hexpm", optional: true]}, {:plug, ">= 0.0.0", [hex: :plug, repo: "hexpm", optional: true]}, {:reactor, "~> 1.0", [hex: :reactor, repo: "hexpm", optional: false]}, {:simple_sat, ">= 0.1.1 and < 1.0.0-0", [hex: :simple_sat, repo: "hexpm", optional: true]}, {:spark, ">= 2.3.14 and < 3.0.0-0", [hex: :spark, repo: "hexpm", optional: false]}, {:splode, "~> 0.3", [hex: :splode, repo: "hexpm", optional: false]}, {:stream_data, "~> 1.0", [hex: :stream_data, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.1", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "adc219ada41d5ec363ef80143404f287d207d0575f93c664a41441d73898306a"},
+  "ash": {:hex, :ash, "3.16.0", "6389927b322ca7fa7990a75730133db44fcff6368adb63f41cf9eec7a5d38862", [:mix], [{:crux, ">= 0.1.2 and < 1.0.0-0", [hex: :crux, repo: "hexpm", optional: false]}, {:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:ecto, "~> 3.7", [hex: :ecto, repo: "hexpm", optional: false]}, {:ets, "~> 0.8", [hex: :ets, repo: "hexpm", optional: false]}, {:igniter, ">= 0.6.29 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, ">= 1.0.0", [hex: :jason, repo: "hexpm", optional: false]}, {:picosat_elixir, "~> 0.2", [hex: :picosat_elixir, repo: "hexpm", optional: true]}, {:plug, ">= 0.0.0", [hex: :plug, repo: "hexpm", optional: true]}, {:reactor, "~> 1.0", [hex: :reactor, repo: "hexpm", optional: false]}, {:simple_sat, ">= 0.1.1 and < 1.0.0-0", [hex: :simple_sat, repo: "hexpm", optional: true]}, {:spark, ">= 2.3.14 and < 3.0.0-0", [hex: :spark, repo: "hexpm", optional: false]}, {:splode, "~> 0.3", [hex: :splode, repo: "hexpm", optional: false]}, {:stream_data, "~> 1.0", [hex: :stream_data, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.1", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "1ea69d932ea2ae6cc2971b92576d8ac2721218a8f2f3599e0e25305edb56949b"},
   "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
   "certifi": {:hex, :certifi, "2.15.0", "0e6e882fcdaaa0a5a9f2b3db55b1394dba07e8d6d9bcad08318fb604c6839712", [:rebar3], [], "hexpm", "b147ed22ce71d72eafdad94f055165c1c182f61a2ff49df28bcc71d1d5b94a60"},
   "credo": {:hex, :credo, "1.7.16", "a9f1389d13d19c631cb123c77a813dbf16449a2aebf602f590defa08953309d4", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "d0562af33756b21f248f066a9119e3890722031b6d199f22e3cf95550e4f1579"},