Revert "Add fallback for PostgreSQL without upsert in CopyStatusStats (…

…mastodon#8903)"

This reverts commit 485dc7d.

db/migrate/20180812173710_copy_status_stats.rb

@@ -3,52 +3,20 @@ class CopyStatusStats < ActiveRecord::Migration[5.2]
 
   def up
     safety_assured do
-      if supports_upsert?
-        up_fast
-      else
-        up_slow
+      Status.unscoped.select('id').find_in_batches(batch_size: 5_000) do |statuses|
+        execute <<-SQL.squish
+          INSERT INTO status_stats (status_id, reblogs_count, favourites_count, created_at, updated_at)
+          SELECT id, reblogs_count, favourites_count, created_at, updated_at
+          FROM statuses
+          WHERE id IN (#{statuses.map(&:id).join(', ')})
+          ON CONFLICT (status_id) DO UPDATE
+          SET reblogs_count = EXCLUDED.reblogs_count, favourites_count = EXCLUDED.favourites_count
+        SQL
       end
     end
   end
 
   def down
     # Nothing
   end
-
-  private
-
-  def supports_upsert?
-    version = select_one("SELECT current_setting('server_version_num') AS v")['v'].to_i
-    version >= 90500
-  end
-
-  def up_fast
-    say 'Upsert is available, importing counters using the fast method'
-
-    Status.unscoped.select('id').find_in_batches(batch_size: 5_000) do |statuses|
-      execute <<-SQL.squish
-        INSERT INTO status_stats (status_id, reblogs_count, favourites_count, created_at, updated_at)
-        SELECT id, reblogs_count, favourites_count, created_at, updated_at
-        FROM statuses
-        WHERE id IN (#{statuses.map(&:id).join(', ')})
-        ON CONFLICT (status_id) DO UPDATE
-        SET reblogs_count = EXCLUDED.reblogs_count, favourites_count = EXCLUDED.favourites_count
-      SQL
-    end
-  end
-
-  def up_slow
-    say 'Upsert is not available in PostgreSQL below 9.5, falling back to slow import of counters'
-
-    # We cannot use bulk INSERT or overarching transactions here because of possible
-    # uniqueness violations that we need to skip over
-    Status.unscoped.select('id, reblogs_count, favourites_count, created_at, updated_at').find_each do |status|
-      begin
-        params = [[nil, status.id], [nil, status.reblogs_count], [nil, status.favourites_count], [nil, status.created_at], [nil, status.updated_at]]
-        exec_insert('INSERT INTO status_stats (status_id, reblogs_count, favourites_count, created_at, updated_at) VALUES ($1, $2, $3, $4, $5)', nil, params)
-      rescue ActiveRecord::RecordNotUnique
-        next
-      end
-    end
-  end
 end