Allow delayed dropping and renaming of tables

db/fixtures/999_delayed.rb

@@ -2,7 +2,7 @@
 
 require 'migration/table_dropper'
 
-Migration::TableDropper.delayed_drop(
+Migration::TableDropper.delayed_rename(
   old_name: 'topic_status_updates',
   new_name: 'topic_timers',
   after_migration: 'RenameTopicStatusUpdatesToTopicTimers',

lib/migration/table_dropper.rb

@@ -2,7 +2,13 @@ require_dependency 'migration/base_dropper'
 
 module Migration
   class Migration::TableDropper < BaseDropper
-    def self.delayed_drop(old_name:, new_name:, after_migration:, delay: nil, on_drop: nil)
+    def self.delayed_drop(table_name:, after_migration:, delay: nil, on_drop: nil)
+      validate_table_name(table_name)
+
+      TableDropper.new(table_name, nil, after_migration, delay, on_drop).delayed_drop
+    end
+
+    def self.delayed_rename(old_name:, new_name:, after_migration:, delay: nil, on_drop: nil)
       validate_table_name(old_name)
       validate_table_name(new_name)
 
@@ -38,9 +44,10 @@ module Migration
         LIMIT 1
       SQL
 
+      builder.where(new_table_exists) if @new_name.present?
+
       builder.where("table_schema = 'public'")
         .where(previous_migration_done)
-        .where(new_table_exists)
         .exec(old_name: @old_name,
               new_name: @new_name,
               delay: "#{@delay} seconds",

spec/components/migration/table_dropper_spec.rb

@@ -4,33 +4,37 @@ require_dependency 'migration/table_dropper'
 describe Migration::TableDropper do
 
   def table_exists?(table_name)
-    sql = <<-SQL
-    SELECT 1
-    FROM INFORMATION_SCHEMA.TABLES
-    WHERE table_schema = 'public' AND
-          table_name = '#{table_name}'
+    sql = <<~SQL
+      SELECT 1
+      FROM INFORMATION_SCHEMA.TABLES
+      WHERE table_schema = 'public' AND
+            table_name = '#{table_name}'
     SQL
 
     ActiveRecord::Base.exec_sql(sql).to_a.length > 0
   end
 
-  describe '#delayed_drop' do
+  let(:migration_name) do
+    ActiveRecord::Base
+      .exec_sql("SELECT name FROM schema_migration_details LIMIT 1")
+      .getvalue(0, 0)
+  end
+
+  before do
+    ActiveRecord::Base.exec_sql "CREATE TABLE table_with_old_name (topic_id INTEGER)"
+
+    Topic.exec_sql("UPDATE schema_migration_details SET created_at = :created_at WHERE name = :name",
+                   name: migration_name, created_at: 15.minutes.ago)
+  end
+
+  describe "#delayed_rename" do
     it "can drop a table after correct delay and when new table exists" do
-      ActiveRecord::Base.exec_sql "CREATE TABLE table_with_old_name (topic_id INTEGER)"
-
-      name = ActiveRecord::Base
-        .exec_sql("SELECT name FROM schema_migration_details LIMIT 1")
-        .getvalue(0, 0)
-
-      Topic.exec_sql("UPDATE schema_migration_details SET created_at = :created_at WHERE name = :name",
-                    name: name, created_at: 15.minutes.ago)
-
       dropped_proc_called = false
 
-      described_class.delayed_drop(
+      described_class.delayed_rename(
         old_name: 'table_with_old_name',
         new_name: 'table_with_new_name',
-        after_migration: name,
+        after_migration: migration_name,
         delay: 20.minutes,
         on_drop: ->() { dropped_proc_called = true }
       )
@@ -38,10 +42,10 @@ describe Migration::TableDropper do
       expect(table_exists?('table_with_old_name')).to eq(true)
       expect(dropped_proc_called).to eq(false)
 
-      described_class.delayed_drop(
+      described_class.delayed_rename(
         old_name: 'table_with_old_name',
         new_name: 'table_with_new_name',
-        after_migration: name,
+        after_migration: migration_name,
         delay: 10.minutes,
         on_drop: ->() { dropped_proc_called = true }
       )
@@ -51,10 +55,36 @@ describe Migration::TableDropper do
 
       ActiveRecord::Base.exec_sql "CREATE TABLE table_with_new_name (topic_id INTEGER)"
 
-      described_class.delayed_drop(
+      described_class.delayed_rename(
         old_name: 'table_with_old_name',
         new_name: 'table_with_new_name',
-        after_migration: name,
+        after_migration: migration_name,
+        delay: 10.minutes,
+        on_drop: ->() { dropped_proc_called = true }
+      )
+
+      expect(table_exists?('table_with_old_name')).to eq(false)
+      expect(dropped_proc_called).to eq(true)
+    end
+  end
+
+  describe "#delayed_drop" do
+    it "can drop a table after correct delay" do
+      dropped_proc_called = false
+
+      described_class.delayed_drop(
+        table_name: 'table_with_old_name',
+        after_migration: migration_name,
+        delay: 20.minutes,
+        on_drop: ->() { dropped_proc_called = true }
+      )
+
+      expect(table_exists?('table_with_old_name')).to eq(true)
+      expect(dropped_proc_called).to eq(false)
+
+      described_class.delayed_drop(
+        table_name: 'table_with_old_name',
+        after_migration: migration_name,
         delay: 10.minutes,
         on_drop: ->() { dropped_proc_called = true }
       )