Extract badge_posts view management logic into a service object.

* Avoid defininig a global constant and method.

Fixes https://github.com/discourse/discourse/pull/6318

db/fixtures/000_delayed_drops.rb

@@ -2,6 +2,7 @@
 
 require 'migration/table_dropper'
 require 'migration/column_dropper'
+require 'badge_posts_view_manager'
 
 Migration::ColumnDropper.drop(
   table: 'user_profiles',
@@ -74,20 +75,6 @@ Migration::ColumnDropper.drop(
   }
 )
 
-VIEW_NAME = "badge_posts".freeze
-
-def badge_posts_view_exists?
-  sql = <<~SQL
-  SELECT 1
-  FROM pg_catalog.pg_views
-  WHERE schemaname
-  IN ('public')
-  AND viewname = '#{VIEW_NAME}';
-  SQL
-
-  DB.exec(sql) == 1
-end
-
 Migration::ColumnDropper.drop(
   table: 'posts',
   after_migration: 'DropVoteCountFromTopicsAndPosts',
@@ -96,27 +83,10 @@ Migration::ColumnDropper.drop(
   },
   on_drop: ->() {
     STDERR.puts "Removing superflous post columns!"
-
+    BadgePostsViewManager.drop!
-    DB.exec("DROP VIEW #{VIEW_NAME}")
-    raise "Failed to drop '#{VIEW_NAME}' view" if badge_posts_view_exists?
   },
   after_drop: -> () {
-    sql = <<~SQL
+    BadgePostsViewManager.create!
-    CREATE VIEW #{VIEW_NAME} AS
-    SELECT p.*
-    FROM posts p
-    JOIN topics t ON t.id = p.topic_id
-    JOIN categories c ON c.id = t.category_id
-    WHERE c.allow_badges AND
-          p.deleted_at IS NULL AND
-          t.deleted_at IS NULL AND
-          NOT c.read_restricted AND
-          t.visible AND
-          p.post_type IN (1,2,3)
-    SQL
-
-    DB.exec(sql)
-    raise "Failed to create '#{VIEW_NAME}' view" unless badge_posts_view_exists?
   }
 )
 

lib/badge_posts_view_manager.rb

@@ -0,0 +1,39 @@
+class BadgePostsViewManager
+  VIEW_NAME = "badge_posts".freeze
+
+  def self.create!
+    sql = <<~SQL
+    CREATE VIEW #{VIEW_NAME} AS
+    SELECT p.*
+    FROM posts p
+    JOIN topics t ON t.id = p.topic_id
+    JOIN categories c ON c.id = t.category_id
+    WHERE c.allow_badges AND
+          p.deleted_at IS NULL AND
+          t.deleted_at IS NULL AND
+          NOT c.read_restricted AND
+          t.visible AND
+          p.post_type IN (1,2,3)
+    SQL
+
+    DB.exec(sql)
+    raise "Failed to create '#{VIEW_NAME}' view" unless badge_posts_view_exists?
+  end
+
+  def self.drop!
+    DB.exec("DROP VIEW #{VIEW_NAME}")
+    raise "Failed to drop '#{VIEW_NAME}' view" if badge_posts_view_exists?
+  end
+
+  def self.badge_posts_view_exists?
+    sql = <<~SQL
+    SELECT 1
+    FROM pg_catalog.pg_views
+    WHERE schemaname
+    IN ('public')
+    AND viewname = '#{VIEW_NAME}';
+    SQL
+
+    DB.exec(sql) == 1
+  end
+end