h3

lib/since/accounts.ex

@@ -768,6 +768,7 @@ defmodule Since.Accounts do
   def get_location_gender_premium_hidden?(user_id) do
     Profile
     |> where(user_id: ^user_id)
+    # TODO
     |> select([p], {p.location, p.gender, p.premium, p.hidden?})
     |> Repo.one!()
   end

lib/since/chats.ex

@@ -3,9 +3,9 @@ defmodule Since.Chats do
 
   import Ecto.{Query, Changeset}
   alias Ecto.Multi
-  import Geo.PostGIS
 
   require Logger
+  require Since.Geo
 
   alias Since.{Repo, Bot}
   alias Since.Chats.{Chat, Message}
@@ -35,15 +35,6 @@ defmodule Since.Chats do
     Phoenix.PubSub.broadcast_from(@pubsub, self(), pubsub_user_topic(user_id), message)
   end
 
-  defmacrop distance_km(location1, location2) do
-    quote do
-      fragment(
-        "round(? / 1000)::int",
-        st_distance_in_meters(unquote(location1), unquote(location2))
-      )
-    end
-  end
-
   def list_chats(user_id, location) do
     Chat
     |> where([c], c.user_id_1 == ^user_id or c.user_id_2 == ^user_id)
@@ -63,10 +54,13 @@ defmodule Since.Chats do
 
     mates = Map.keys(mate_chats)
 
+    %Geo.Point{coordinates: {user_lon, user_lat}, srid: 4326} = location
+    location_h3 = :h3.from_geo({user_lat, user_lon}, 7)
+
     profiles =
       FeedProfile
       |> where([p], p.user_id in ^mates)
-      |> select([p], %{p | distance: distance_km(^location, p.location)})
+      |> select([p], %{p | distance: Since.Geo.distance_km(^location_h3, p.h3)})
       |> Repo.all()
       |> Map.new(fn profile -> {profile.user_id, profile} end)
 

lib/since/feeds.ex

@@ -3,9 +3,9 @@ defmodule Since.Feeds do
 
   import Ecto.{Query, Changeset}
   alias Ecto.Multi
-  import Geo.PostGIS
 
   require Logger
+  require Since.Geo
 
   alias Since.{Repo, Bot}
 
@@ -43,15 +43,6 @@ defmodule Since.Feeds do
     Phoenix.PubSub.broadcast(@pubsub, pubsub_user_topic(user_id), message)
   end
 
-  defmacrop distance_km(location1, location2) do
-    quote do
-      fragment(
-        "round(? / 1000)::int",
-        st_distance_in_meters(unquote(location1), unquote(location2))
-      )
-    end
-  end
-
   ### Feed
 
   @feed_fetch_count 10
@@ -188,14 +179,18 @@ defmodule Since.Feeds do
   end
 
   defp first_time_user_feed(user_id, location, gender, feed_filter, count) do
+    location_h3 = Since.Geo.point_to_h3(location)
+
     feed_profiles_q(user_id, gender, feed_filter.genders)
     |> where([p], p.times_liked >= ^@quality_likes_count_treshold)
     |> where([p], fragment("jsonb_array_length(?) > 2", p.story))
-    |> order_by(fragment("location <-> ?::geometry", ^location))
+    |> order_by([p],
+      asc_nulls_last: fragment("h3_grid_distance(?, ?)", ^location_h3, p.h3)
+    )
     |> maybe_apply_age_filters(feed_filter)
-    |> maybe_apply_distance_filter(location, feed_filter.distance)
+    |> maybe_apply_distance_filter(feed_filter.distance)
     |> limit(^count)
-    |> select([p], %{p | distance: distance_km(^location, p.location)})
+    |> select([p], %{p | distance: Since.Geo.distance_km(^location_h3, p.h3)})
     |> Repo.all()
   end
 
@@ -208,25 +203,31 @@ defmodule Since.Feeds do
          feed_filter,
          count
        ) do
+    %Geo.Point{coordinates: {search_lon, search_lat}, srid: 4326} = location
+    location_h3 = :h3.from_geo({search_lat, search_lon}, 7)
+
     feed_profiles_q(user_id, gender, feed_filter.genders)
     |> where([p], p.user_id not in ^calculated_feed_ids)
     |> where([p], p.user_id not in subquery(feeded_ids_q))
     |> not_seen_profiles_q(user_id)
-    |> order_by(fragment("location <-> ?::geometry", ^location))
+    |> order_by(fragment("h3_grid_distance(?, ?)", ^location_h3, p.h3))
     |> maybe_apply_age_filters(feed_filter)
-    |> maybe_apply_distance_filter(location, feed_filter.distance)
+    |> maybe_apply_distance_filter(feed_filter.distance)
     |> limit(^count)
-    |> select([p], %{p | distance: distance_km(^location, p.location)})
+    |> select([p], %{p | distance: Since.Geo.distance_km(^location_h3, p.h3)})
     |> Repo.all()
   end
 
   defp preload_feed_profiles(profile_ids, user_id, location, gender, feed_filter) do
+    %Geo.Point{coordinates: {search_lon, search_lat}, srid: 4326} = location
+    location_h3 = :h3.from_geo({search_lat, search_lon}, 7)
+
     feed_profiles_q(user_id, gender, feed_filter.genders)
     |> where([p], p.user_id in ^profile_ids)
     |> maybe_apply_age_filters(feed_filter)
-    |> maybe_apply_distance_filter(location, feed_filter.distance)
+    |> maybe_apply_distance_filter(feed_filter.distance)
     |> limit(^@feed_fetch_count)
-    |> select([p], %{p | distance: distance_km(^location, p.location)})
+    |> select([p], %{p | distance: Since.Geo.distance_km(^location_3, p.h3)})
     |> Repo.all()
   end
 
@@ -246,15 +247,18 @@ defmodule Since.Feeds do
          feeded_ids_q,
          feed_filter
        ) do
+    %Geo.Point{coordinates: {search_lon, search_lat}, srid: 4326} = location
+    location_h3 = :h3.from_geo({search_lat, search_lon}, 7)
+
     feed_profiles_q(user_id, gender, feed_filter.genders)
     |> where([p], p.user_id not in subquery(feeded_ids_q))
     |> join(:left, [p, g], s in SeenProfile, on: [user_id: p.user_id, by_user_id: ^user_id])
     |> maybe_filter_by_sticker(feed_category)
     |> order_by_feed_category(feed_category, location)
     |> maybe_apply_age_filters(feed_filter)
-    |> maybe_apply_distance_filter(location, feed_filter.distance)
+    |> maybe_apply_distance_filter(feed_filter.distance)
     |> limit(^@feed_fetch_count)
-    |> select([p, g, s], %{p | distance: distance_km(^location, p.location)})
+    |> select([p, g, s], %{p | distance: Since.Geo.distance_km(^location_h3, p.h3)})
     |> Repo.all()
   end
 
@@ -313,10 +317,9 @@ defmodule Since.Feeds do
     end
   end
 
-  defp maybe_apply_distance_filter(query, location, distance) do
+  defp maybe_apply_distance_filter(query, distance) do
     if distance do
-      meters = distance * 1000
-      where(query, [p], st_dwithin_in_meters(^location, p.location, ^meters))
+      having(query, [p], p.distance <= ^distance)
     else
       query
     end
@@ -352,9 +355,12 @@ defmodule Since.Feeds do
 
   @spec get_mate_feed_profile(Ecto.UUID.t(), Geo.Point.t()) :: %FeedProfile{} | nil
   def get_mate_feed_profile(user_id, location) do
+    %Geo.Point{coordinates: {lon, lat}, srid: 4326} = location
+    location_h3 = :h3.from_geo({lat, lon}, 7)
+
     not_hidden_profiles_q()
     |> where(user_id: ^user_id)
-    |> select([p], %{p | distance: distance_km(^location, p.location)})
+    |> select([p], %{p | distance: Since.Geo.distance_km(^location_h3, p.h3)})
     |> Repo.one()
   end
 

lib/since/geo.ex

@@ -0,0 +1,20 @@
+defmodule Since.Geo do
+  @moduledoc "Helpers for working with geographic data."
+  import Ecto.Query
+
+  @spec point_to_h3(Geo.Point.t()) :: :h3.h3_index()
+  def point_to_h3(point) do
+    %Geo.Point{coordinates: {lon, lat}, srid: 4326} = point
+    :h3.from_geo({lat / 1, lon / 1}, 7)
+  end
+
+  @doc """
+  Computes [approximated](https://jonisalonen.com/2014/computing-distance-between-coordinates-can-be-simple-and-fast/)
+  distance in kilometers between two H3 indexes.
+  """
+  defmacro fast_distance_km(target_h3, origin_h3) do
+    quote do
+      fragment("fast_distance_km(?,?)", unquote(target_h3), unquote(origin_h3))
+    end
+  end
+end

lib/since_web/channels/feed_channel.ex

@@ -51,6 +51,7 @@ defmodule SinceWeb.FeedChannel do
   defp join_normal_mode(user_id, params, socket) do
     feed_filter = Feeds.get_feed_filter(user_id)
 
+    # TODO
     {old_location, gender, premium, hidden?} =
       Accounts.get_location_gender_premium_hidden?(user_id)
 

lib/since_web/views/profile_view.ex

@@ -5,10 +5,12 @@ defmodule SinceWeb.ProfileView do
   alias Since.Accounts.Profile
 
   def render("show_with_location.json", %{
-        profile: %Profile{location: location} = profile,
+        profile: %Profile{h3: h3} = profile,
         screen_width: screen_width,
         version: version
       }) do
+    {lat, lon} = if h3, do: :h3.to_geo(h3), else: {nil, nil}
+
     profile
     |> render_profile(
       [
@@ -27,16 +29,10 @@ defmodule SinceWeb.ProfileView do
       screen_width,
       _env = :profile
     )
-    |> Map.put(:latitude, lat(location))
-    |> Map.put(:longitude, lon(location))
+    |> Map.put(:latitude, lat)
+    |> Map.put(:longitude, lon)
   end
 
-  defp lat(%Geo.Point{coordinates: {_lon, lat}}), do: lat
-  defp lat(nil), do: nil
-
-  defp lon(%Geo.Point{coordinates: {lon, _lat}}), do: lon
-  defp lon(nil), do: nil
-
   defp render_profile(%Profile{story: story} = profile, fields, version, screen_width, env) do
     profile
     |> Map.take(fields)

test/t_web/channels/feed_channel_test.exs

@@ -203,7 +203,7 @@ defmodule SinceWeb.FeedChannelTest do
                    story: [],
                    user_id: p3.id,
                    gender: "M",
-                   distance: 9510,
+                   distance: 9485,
                    address: %{
                      "en_US" => %{
                        "city" => "Buenos Aires",
@@ -248,7 +248,7 @@ defmodule SinceWeb.FeedChannelTest do
                    story: [],
                    user_id: p2.id,
                    gender: "N",
-                   distance: 9510,
+                   distance: 9485,
                    address: %{
                      "en_US" => %{
                        "city" => "Buenos Aires",
@@ -277,7 +277,7 @@ defmodule SinceWeb.FeedChannelTest do
                    story: [],
                    user_id: p1.id,
                    gender: "F",
-                   distance: 9510,
+                   distance: 9485,
                    address: %{
                      "en_US" => %{
                        "city" => "Buenos Aires",