Bugfix for :preload, and support ORDER BY query

lib/etso/adapter/behaviour/queryable.ex

@@ -3,6 +3,7 @@ defmodule Etso.Adapter.Behaviour.Queryable do
 
   alias Etso.Adapter.TableRegistry
   alias Etso.ETS.MatchSpecification
+  alias Etso.ETS.TableSorter
 
   def prepare(:all, query) do
     {:nocache, query}
@@ -12,7 +13,12 @@ defmodule Etso.Adapter.Behaviour.Queryable do
     {_, schema} = query.from.source
     {:ok, ets_table} = TableRegistry.get_table(repo, schema)
     ets_match = MatchSpecification.build(query, params)
-    ets_objects = :ets.select(ets_table, [ets_match])
+
+    ets_objects =
+      ets_table
+      |> :ets.select([ets_match])
+      |> TableSorter.sort(query)
+
     {length(ets_objects), ets_objects}
   end
 

lib/etso/ets/table_sorter.ex

@@ -0,0 +1,61 @@
+defmodule Etso.ETS.TableSorter do
+  @moduledoc """
+  This module is used to sort the list of ETS objects based
+  on the order by clause and fields in the query.
+  """
+
+  def sort(ets_objects, query) do
+    orders =
+      Enum.flat_map(query.order_bys, fn %{expr: order_bys} ->
+        Enum.map(order_bys, fn {order, {{:., [], [{:&, [], [0]}, field]}, [], []}} ->
+          {field, order}
+        end)
+      end)
+
+    select_fields =
+      Enum.map(query.select.fields, fn {{:., _, [{:&, [], [0]}, field]}, [], []} -> field end)
+
+    ets_objects
+    |> Enum.map(fn object ->
+      select_fields
+      |> Enum.zip(object)
+      |> Enum.into(%{})
+    end)
+    |> Enum.sort_by(& &1, build_sorter(orders))
+    |> Enum.map(fn object -> Enum.map(select_fields, &Map.fetch!(object, &1)) end)
+  end
+
+  defp build_sorter(sort_keys) do
+    sort_keys
+    |> Enum.reverse()
+    |> Enum.reduce(fn _, _ -> true end, fn {key, order}, acc ->
+      build_sorter_by_order(order, key, acc)
+    end)
+  end
+
+  def build_sorter_by_order(:asc, key, next_cond_fun) do
+    fn lhs, rhs ->
+      lval = Map.fetch!(lhs, key)
+      rval = Map.fetch!(rhs, key)
+
+      cond do
+        lval < rval -> true
+        lval > rval -> false
+        true -> next_cond_fun.(lhs, rhs)
+      end
+    end
+  end
+
+  def build_sorter_by_order(:desc, key, next_cond_fun) do
+    fn lhs, rhs ->
+      lval = Map.fetch!(lhs, key)
+      rval = Map.fetch!(rhs, key)
+
+      cond do
+        lval > rval -> true
+        lval < rval -> false
+        true -> next_cond_fun.(lhs, rhs)
+      end
+    end
+  end
+end

test/ets/table_sorter_test.exs

@@ -0,0 +1,175 @@
+defmodule ETS.TableSorterTest do
+  use ExUnit.Case
+
+  describe "sort/2" do
+    test "sort ets_objects" do
+      query = dummy_query()
+      ets_objects = dummy_ets_objects()
+
+      [object1, object2, object3, object4, object5] = ets_objects
+
+      [result1, result2, result3, result4, result5] =
+        Etso.ETS.TableSorter.sort(ets_objects, query)
+
+      assert object1 == result1
+      assert object2 == result2
+      assert object3 == result4
+      assert object4 == result3
+      assert object5 == result5
+    end
+  end
+
+  def dummy_query() do
+    %Ecto.Query{
+      select: %Ecto.Query.SelectExpr{
+        fields: [
+          {{:., [], [{:&, [], [0]}, :order_id]}, [], []},
+          {{:., [], [{:&, [], [0]}, :customer_id]}, [], []},
+          {{:., [], [{:&, [], [0]}, :employee_id]}, [], []},
+          {{:., [], [{:&, [], [0]}, :freight]}, [], []},
+          {{:., [], [{:&, [], [0]}, :order_date]}, [], []},
+          {{:., [], [{:&, [], [0]}, :required_date]}, [], []},
+          {{:., [], [{:&, [], [0]}, :ship_name]}, [], []},
+          {{:., [], [{:&, [], [0]}, :ship_via]}, [], []},
+          {{:., [], [{:&, [], [0]}, :shipped_date]}, [], []},
+          {{:., [], [{:&, [], [0]}, :ship_address]}, [], []},
+          {{:., [], [{:&, [], [0]}, :details]}, [], []},
+          {{:., [type: :integer], [{:&, [], [0]}, :ship_via]}, [], []}
+        ]
+      },
+      order_bys: [
+        %Ecto.Query.QueryExpr{
+          expr: [asc: {{:., [], [{:&, [], [0]}, :ship_via]}, [], []}]
+        }
+      ]
+    }
+  end
+
+  def dummy_ets_objects() do
+    [
+      [
+        10309,
+        "HUNGO",
+        3,
+        47.3,
+        ~D[1996-09-19],
+        ~D[1996-10-17],
+        "Hungry Owl All-Night Grocers",
+        1,
+        ~D[1996-10-23],
+        %{
+          city: "Cork",
+          country: "Ireland",
+          phone: nil,
+          postal_code: nil,
+          region: "Co. Cork",
+          street: "8 Johnstown Road"
+        },
+        [
+          %{discount: 0.0, product_id: nil, quantity: 20, unit_price: nil},
+          %{discount: 0.0, product_id: nil, quantity: 30, unit_price: nil},
+          %{discount: 0.0, product_id: nil, quantity: 2, unit_price: nil},
+          %{discount: 0.0, product_id: nil, quantity: 20, unit_price: nil},
+          %{discount: 0.0, product_id: nil, quantity: 3, unit_price: nil}
+        ],
+        1
+      ],
+      [
+        10269,
+        "WHITC",
+        5,
+        4.56,
+        ~D[1996-07-31],
+        ~D[1996-08-14],
+        "White Clover Markets",
+        1,
+        ~D[1996-08-09],
+        %{
+          city: "Seattle",
+          country: "USA",
+          phone: nil,
+          postal_code: "98124",
+          region: "WA",
+          street: "1029 - 12th Ave. S."
+        },
+        [
+          %{discount: 0.05, product_id: nil, quantity: 60, unit_price: nil},
+          %{discount: 0.05, product_id: nil, quantity: 20, unit_price: nil}
+        ],
+        1
+      ],
+      [
+        10677,
+        "ANTON",
+        1,
+        4.03,
+        ~D[1997-09-22],
+        ~D[1997-10-20],
+        "Antonio Moreno Taquería",
+        3,
+        ~D[1997-09-26],
+        %{
+          city: "México D.F.",
+          country: "Mexico",
+          phone: nil,
+          postal_code: "5023",
+          region: nil,
+          street: "Mataderos  2312"
+        },
+        [
+          %{discount: 0.15, product_id: nil, quantity: 30, unit_price: nil},
+          %{discount: 0.15, product_id: nil, quantity: 8, unit_price: nil}
+        ],
+        3
+      ],
+      [
+        10301,
+        "WANDK",
+        8,
+        45.08,
+        ~D[1996-09-09],
+        ~D[1996-10-07],
+        "Die Wandernde Kuh",
+        2,
+        ~D[1996-09-17],
+        %{
+          city: "Stuttgart",
+          country: "Germany",
+          phone: nil,
+          postal_code: "70563",
+          region: nil,
+          street: "Adenauerallee 900"
+        },
+        [
+          %{discount: 0.0, product_id: nil, quantity: 10, unit_price: nil},
+          %{discount: 0.0, product_id: nil, quantity: 20, unit_price: nil}
+        ],
+        2
+      ],
+      [
+        10542,
+        "KOENE",
+        1,
+        10.95,
+        ~D[1997-05-20],
+        ~D[1997-06-17],
+        "Königlich Essen",
+        3,
+        ~D[1997-05-26],
+        %{
+          city: "Brandenburg",
+          country: "Germany",
+          phone: nil,
+          postal_code: "14776",
+          region: nil,
+          street: "Maubelstr. 90"
+        },
+        [
+          %{discount: 0.05, product_id: nil, quantity: 15, unit_price: nil},
+          %{discount: 0.05, product_id: nil, quantity: 24, unit_price: nil}
+        ],
+        3
+      ]
+    ]
+  end
+end

test/northwind/repo_test.exs

@@ -128,4 +128,26 @@ defmodule Northwind.RepoTest do
     |> Repo.all()
     |> Repo.preload(shipper: :orders)
   end
+
+  test "Order / Shipper / Orders Preloading before all()" do
+    Model.Order
+    |> preload([_x], shipper: :orders)
+    |> Repo.all()
+  end
+
+  test "Order By Desc company_name, Asc phone" do
+    unsorted_shippers =
+      Model.Shipper
+      |> Repo.all()
+
+    sorted_shippers =
+      Model.Shipper
+      |> order_by([x], desc: x.company_name, asc: x.phone)
+      |> Repo.all()
+
+    assert sorted_shippers ==
+             unsorted_shippers
+             |> Enum.sort_by(& &1.company_name, :desc)
+             |> Enum.sort_by(& &1.phone)
+  end
 end