Squash accounts balance history table

lib/ex_money/accounts/accounts.ex

@@ -0,0 +1,27 @@
+defmodule ExMoney.Accounts do
+  @moduledoc """
+  The Accounts context.
+  """
+
+  import Ecto.Query, warn: false
+  alias ExMoney.Repo
+
+  alias ExMoney.Accounts.BalanceHistory
+
+  def get_account_history_balance(from, to) do
+    {:ok, from} = Date.from_iso8601(from)
+    erl_from = Date.to_erl(from)
+    {:ok, naive_from} = NaiveDateTime.from_erl({erl_from, {0, 0, 0}})
+
+    {:ok, to} = Date.from_iso8601(to)
+    erl_to = Date.to_erl(to)
+    {:ok, naive_to} = NaiveDateTime.from_erl({erl_to, {0, 0, 0}})
+
+    query =
+      from h in BalanceHistory,
+        where: h.inserted_at >= ^naive_from,
+        where: h.inserted_at <= ^naive_to
+
+    Repo.all(query)
+  end
+end

lib/ex_money/accounts/balance_history.ex

@@ -0,0 +1,16 @@
+defmodule ExMoney.Accounts.BalanceHistory do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  schema "accounts_balance_history" do
+    field :state, :map
+
+    timestamps()
+  end
+
+  def changeset(model, params \\ %{}) do
+    model
+    |> cast(params, ~w(state)a)
+    |> validate_required(~w(state)a)
+  end
+end

lib/ex_money/accounts_balance_history_worker.ex

@@ -1,20 +1,24 @@
 defmodule ExMoney.AccountsBalanceHistoryWorker do
   use GenServer
 
-  alias ExMoney.{Account, Repo, AccountsBalanceHistory}
+  alias ExMoney.{Repo, Account}
+  alias ExMoney.Accounts.BalanceHistory
 
   def start_link(_opts \\ []) do
     GenServer.start_link(__MODULE__, :ok, name: :accounts_balance_history_worker)
   end
 
   def handle_call(:store_current_balance, _from, state) do
-    Account
-    |> Repo.all
-    |> Enum.each(fn(account) ->
-      %AccountsBalanceHistory{}
-      |> AccountsBalanceHistory.changeset(%{account_id: account.id, balance: account.balance})
-      |> Repo.insert!
-    end)
+    accounts_state =
+      Account
+      |> Repo.all
+      |> Enum.reduce(%{}, fn(account, acc) ->
+        Map.put(acc, account.id, account.balance)
+      end)
+
+    %BalanceHistory{}
+    |> BalanceHistory.changeset(%{state: accounts_state})
+    |> Repo.insert!
 
     {:reply, :stored, state}
   end

lib/ex_money_web/controllers/mobile/account_controller.ex

@@ -2,7 +2,7 @@ defmodule ExMoney.Web.Mobile.AccountController do
   use ExMoney.Web, :controller
 
   alias ExMoney.DateHelper
-  alias ExMoney.{Repo, Transaction, Account, AccountsBalanceHistory}
+  alias ExMoney.{Repo, Transaction, Account}
 
   plug Guardian.Plug.EnsureAuthenticated, handler: ExMoney.Guardian.Mobile.Unauthenticated
   plug :put_layout, "mobile.html"
@@ -99,15 +99,14 @@ defmodule ExMoney.Web.Mobile.AccountController do
   end
 
   defp account_balance(from, to, account_id) do
-    AccountsBalanceHistory.history(from, to, account_id)
-    |> Repo.all
-    |> Enum.reduce(%{}, fn(h, acc) ->
+    ExMoney.Accounts.get_account_history_balance(from, to)
+    |> Enum.reduce(%{}, fn(history, acc) ->
       inserted_at =
-        h.inserted_at
+        history.inserted_at
         |> NaiveDateTime.to_date()
         |> Date.to_string()
 
-      Map.put(acc, inserted_at, h.balance)
+      Map.put(acc, inserted_at, history.state[to_string(account_id)])
     end)
   end
 

lib/ex_money_web/models/account.ex

@@ -22,9 +22,6 @@ defmodule ExMoney.Account do
       foreign_key: :saltedge_account_id,
       references: :saltedge_account_id
 
-    has_many :balance_history, ExMoney.AccountsBalanceHistory,
-      on_delete: :delete_all
-
     timestamps()
   end
 

lib/ex_money_web/views/shared_view.ex

@@ -21,7 +21,7 @@ defmodule ExMoney.Web.SharedView do
   end
 
   def description(transaction) do
-    String.replace(transaction.extra["payee"], ~r/\A[A-Z]{2}\w{15,32}/, "")
+    String.replace(transaction.extra["payee"] || "", ~r/\A[A-Z]{2}\w{15,32}/, "")
   end
 
   def category_name(nil), do: ""
@@ -33,9 +33,11 @@ defmodule ExMoney.Web.SharedView do
   def account_balance(_date, _, nil), do: ""
   def account_balance(date, account_balance, account) do
     date = to_string(date)
-    case account_balance[date] do
-      nil -> ""
-      balance -> "#{balance} #{account.currency_label}"
+    balance = account_balance[date]
+    if balance do
+      "#{balance} #{account.currency_label}"
+    else
+      ""
     end
   end
 end

lib/mix/tasks/account_history_balance_state.ex

@@ -0,0 +1,43 @@
+defmodule Mix.Tasks.ExMoney.AccountsHistoryBalanceState do
+  use Mix.Task
+  import Mix.Ecto
+  import Ecto.Query, warn: false
+
+  alias ExMoney.{Repo, Accounts.BalanceHistory}
+
+  @shortdoc "Move balance history entries into `state` map field to reduce number of rows"
+
+  def run(_args) do
+    ensure_repo(ExMoney.Repo, [])
+    ensure_started(ExMoney.Repo, [])
+
+    query = from h in BalanceHistory,
+      group_by: fragment("inserted_at::timestamp::date"),
+      select: %{
+        min_id: min(h.id),
+        grouped_json: fragment("json_agg(json_build_object('id', id, 'account_id', account_id, 'balance', balance))")
+      }
+
+    h = Repo.all(query)
+
+    Enum.each h, fn(%{min_id: id, grouped_json: grouped_json}) ->
+      accounts_state = Enum.reduce grouped_json, %{}, fn(row, acc) ->
+        Map.put(acc, row["account_id"], row["balance"])
+      end
+
+      ids_to_remove = Enum.reduce grouped_json, [], fn(row, acc) ->
+        if row["id"] != id do
+          [row["id"] | acc]
+        else
+          acc
+        end
+      end
+
+      Repo.get(BalanceHistory, id)
+      |> BalanceHistory.changeset(%{state: accounts_state})
+      |> Repo.update!
+
+      (from h in BalanceHistory, where: h.id in ^ids_to_remove) |> Repo.delete_all
+    end
+  end
+end

priv/repo/migrations/20180211210647_add_state_to_balance_history.exs

@@ -0,0 +1,9 @@
+defmodule ExMoney.Repo.Migrations.AddStateToBalanceHistory do
+  use Ecto.Migration
+
+  def change do
+    alter table(:accounts_balance_history) do
+      add :state, :map
+    end
+  end
+end

test/lib/accounts_balance_history_worker_test.exs

@@ -1,7 +1,7 @@
 defmodule ExMoney.AccountsBalanceHistoryWorkerTest do
   use ExUnit.Case
 
-  alias ExMoney.{AccountsBalanceHistory, Repo}
+  alias ExMoney.{Accounts.BalanceHistory, Repo}
 
   import ExMoney.Factory
 
@@ -18,10 +18,8 @@ defmodule ExMoney.AccountsBalanceHistoryWorkerTest do
   test "store current balance", %{account_1: account_1, account_2: account_2} do
     assert :stored == GenServer.call(:accounts_balance_history_worker, :store_current_balance)
 
-    history_1 = Repo.get_by(AccountsBalanceHistory, account_id: account_1.id)
-    history_2 = Repo.get_by(AccountsBalanceHistory, account_id: account_2.id)
+    h = Repo.all(BalanceHistory) |> List.first
 
-    assert Decimal.new(10) == history_1.balance
-    assert Decimal.new(20) == history_2.balance
+    assert h.state == %{to_string(account_1.id) => "10", to_string(account_2.id) => "20"}
   end
 end

test/support/factory.ex

@@ -31,9 +31,8 @@ defmodule ExMoney.Factory do
   end
 
   def accounts_balance_history do
-    %ExMoney.AccountsBalanceHistory {
-      account: build(:account),
-      balance: Decimal.new(10)
+    %ExMoney.Accounts.BalanceHistory {
+      state: %{"1" => Decimal.new(10)}
     }
   end