Update to support ecto 3 + switch to using Process dictionary

lib/one_plus_n_detector.ex

@@ -1,6 +1,4 @@
 defmodule OnePlusNDetector do
-  use Application
-
   @moduledoc """
   Ecto Repo's logger adapter.
 
@@ -10,32 +8,55 @@ defmodule OnePlusNDetector do
       ]
   """
 
+  require Logger
   alias OnePlusNDetector.Detector
 
-  @impl true
-  def start(_type, _args) do
-    import Supervisor.Spec, warn: false
+  @exclude_sources ["oban_jobs", "oban_peers"]
+  @exclude_queries ["commit", "begin"]
+  @exclude_match ["oban_jobs", "oban_peers", "oban_insert", "pg_notify", "pg_try_advisory_xact_lock"]
+
+  def setup(repo_module) do
+    config = repo_module.config()
+    prefix = config[:telemetry_prefix]
+    # ^ Telemetry event id for Ecto queries
+    query_event = prefix ++ [:query]
+
+    Logger.debug "Setting up n+1 logging..."
 
-    children = [
-      worker(OnePlusNDetector.Detector, []),
-    ]
+    :telemetry.attach(
+      "one_plus_n_detector",
+      query_event,
+      &OnePlusNDetector.handle_event/4,
+      []
+    )
+  end
 
-    Supervisor.start_link(children, strategy: :one_for_one)
+  def handle_event(
+        _,
+        _measurements,
+        %{query: query, source: source} = _metadata,
+        _config
+      )
+      when (is_nil(source) or source not in @exclude_sources) and
+             query not in @exclude_queries do
+   if not String.contains?(query, @exclude_match), do: analyze(query)
   end
 
-  def analyze(%Ecto.LogEntry{query: query} = entry) do
-    # We need to make sure our app is started or start it ourselves
-    {:ok, _} = Application.ensure_all_started(:one_plus_n_detector)
+  def handle_event(
+        _,
+        _measurements,
+        _metadata,
+        _config
+      ) do
+   # skip
+  end
 
+  def analyze(query) do
     case Detector.check(query) do
-      {:match, _query, _count} ->
-        :nothing
-      {:no_match, _previous_query, count} ->
-        if count > 2 do
-          IO.puts "---------> 1+n SQL query detected, total count: #{count}"
-        end
+      {:match, count} ->
+          Logger.warning "---------> Possible n+1 SQL query detected! number of occurrences: #{count}, query: #{query}"
+      _ ->
+        # no match
     end
-
-    entry
   end
 end

lib/one_plus_n_detector/detector.ex

@@ -3,38 +3,32 @@ defmodule OnePlusNDetector.Detector do
   Checks a query against the previous one and increments counter of collisions or swaps previous query with the last one.
   """
 
-  use GenServer
-
   # Increase counter or swaps query
   def check("SELECT" <> _rest = query) do
-    GenServer.call(__MODULE__, {:check, query})
+    do_check(query, get(query))
   end
 
   def check(_query) do
-    GenServer.call(__MODULE__, :reset)
+    nil
   end
 
-  def start_link() do
-    GenServer.start_link(__MODULE__, %{query: nil, counter: 0}, name: __MODULE__)
+  defp get(query) do
+    Process.get("one_plus_n_detector: #{query}")
   end
 
-  @impl true
-  def init(state) do
-    {:ok, state}
+  defp put(query, counter) do
+    Process.put("one_plus_n_detector: #{query}", counter)
   end
 
-  @impl true
-  def handle_call({:check, query}, _from, %{query: query, counter: counter} = state) do
-    {:reply, {:match, query, counter + 1}, Map.put(state, :counter, counter + 1)}
+  def do_check(query, nil) do
+    put(query, 1)
+    :first
   end
 
-  @impl true
-  def handle_call({:check, query}, _from, %{query: previous_query, counter: previous_count}) do
-    {:reply, {:no_match, previous_query, previous_count}, %{query: query, counter: 1}}
+  def do_check(query, counter) do
+    counter = counter + 1
+    put(query, counter)
+    {:match, counter}
   end
 
-  @impl true
-  def handle_call(:reset, _from, %{query: previous_query, counter: previous_count}) do
-    {:reply, {:no_match, previous_query, previous_count}, %{query: nil, counter: 0}}
-  end
 end

mix.exs

@@ -15,14 +15,13 @@ defmodule OnePlusNDetector.MixProject do
 
   def application do
     [
-      extra_applications: [:logger],
-      mod: {OnePlusNDetector, []}
+      extra_applications: [:logger]
     ]
   end
 
   defp deps do
     [
-      {:ecto, "~> 2.0"},
+      {:ecto, "~> 3.0"},
       {:ex_doc, ">= 0.0.0", only: :dev},
     ]
   end