PERF: N+1 query on groups page.

app/assets/javascripts/discourse/components/group-membership-button.js.es6

@@ -12,6 +12,15 @@ export default Ember.Component.extend({
     return !!(this.currentUser) && allowMembershipRequests && aliasLevel === 99;
   },
 
+  @computed("model.is_group_user", "model.id", "groupUserIds")
+  userIsGroupUser(isGroupUser, groupId, groupUserIds) {
+    if (isGroupUser) {
+      return isGroupUser;
+    } else {
+      return groupUserIds.includes(groupId);
+    }
+  },
+
   actions: {
     joinGroup() {
       this.set('updatingMembership', true);

app/assets/javascripts/discourse/templates/components/group-membership-button.hbs

@@ -1,5 +1,5 @@
 {{#if canJoinGroup}}
-  {{#if model.is_group_user}}
+  {{#if userIsGroupUser}}
     {{d-button action="leaveGroup"
         class="btn-danger group-index-leave"
         icon="minus"
@@ -13,7 +13,7 @@
         disabled=updatingMembership}}
   {{/if}}
 {{else if canRequestMembership}}
-  {{#if model.is_group_user}}
+  {{#if userIsGroupUser}}
     {{#if showMembershipStatus}}
       {{d-button
           class="btn-primary"

app/assets/javascripts/discourse/templates/groups.hbs

@@ -1,6 +1,5 @@
 {{#d-section pageClass="groups"}}
   <h1>{{i18n "groups.index.title"}}</h1>
-
   {{#if groups}}
     {{#load-more selector=".groups-table .groups-table-row" action="loadMore"}}
       <div class='container'>
@@ -47,7 +46,8 @@
                 <td>
                   {{#group-membership-button model=group
                       createNewMessageViaParams='createNewMessageViaParams'
-                      showMembershipStatus=true}}
+                      showMembershipStatus=true
+                      groupUserIds=groups.extras.group_user_ids}}
 
                     {{d-button icon="ban"
                         label=(if group.automatic 'groups.automatic_group' 'groups.closed_group')

app/controllers/groups_controller.rb

@@ -23,11 +23,16 @@ class GroupsController < ApplicationController
     count = groups.count
     groups = groups.offset(page * page_size).limit(page_size)
 
-    render json: {
+    group_user_ids = GroupUser.where(group: groups, user: current_user).pluck(:group_id)
-      groups: serialize_data(groups, GroupShowSerializer),
+
+    render_json_dump(
+      groups: serialize_data(groups, BasicGroupSerializer),
+      extras: {
+        group_user_ids: group_user_ids
+      },
       total_rows_groups: count,
       load_more_groups: groups_path(page: page + 1)
-    }
+    )
   end
 
   def show