Only use DROP INDEX CONCURRENTLY on postgreql 9.2+

.gitlab-ci.yml

@@ -52,7 +52,7 @@ stages:
 
 .use-pg: &use-pg
   services:
-    - postgres:9.2
+    - postgres:9.1
     - redis:alpine
 
 .use-mysql: &use-mysql

db/migrate/20170317203554_index_routes_path_for_like.rb

@@ -21,9 +21,8 @@ def up
 
   def down
     return unless Gitlab::Database.postgresql?
+    return unless index_exists?(:routes, :path, name: INDEX_NAME)
 
-    if index_exists?(:routes, :path, name: INDEX_NAME)
-      execute("DROP INDEX CONCURRENTLY #{INDEX_NAME};")
-    end
+    remove_concurrent_index_by_name(:routes, INDEX_NAME)
   end
 end

db/migrate/20170402231018_remove_index_for_users_current_sign_in_at.rb

@@ -11,13 +11,7 @@ class RemoveIndexForUsersCurrentSignInAt < ActiveRecord::Migration
   disable_ddl_transaction!
 
   def up
-    if index_exists? :users, :current_sign_in_at
-      if Gitlab::Database.postgresql?
-        execute 'DROP INDEX CONCURRENTLY index_users_on_current_sign_in_at;'
-      else
-        remove_concurrent_index :users, :current_sign_in_at
-      end
-    end
+    remove_concurrent_index :users, :current_sign_in_at
   end
 
   def down

db/migrate/20170503185032_index_redirect_routes_path_for_like.rb

@@ -21,9 +21,8 @@ def up
 
   def down
     return unless Gitlab::Database.postgresql?
+    return unless index_exists?(:redirect_routes, :path, name: INDEX_NAME)
 
-    if index_exists?(:redirect_routes, :path, name: INDEX_NAME)
-      execute("DROP INDEX CONCURRENTLY #{INDEX_NAME};")
-    end
+    remove_concurrent_index_by_name(:redirect_routes, INDEX_NAME)
   end
 end

lib/gitlab/database/migration_helpers.rb

@@ -42,7 +42,7 @@ def remove_concurrent_index(table_name, column_name, options = {})
             'in the body of your migration class'
         end
 
-        if Database.postgresql?
+        if supports_drop_index_concurrently?
           options = options.merge({ algorithm: :concurrently })
           disable_statement_timeout
         end
@@ -50,6 +50,39 @@ def remove_concurrent_index(table_name, column_name, options = {})
         remove_index(table_name, options.merge({ column: column_name }))
       end
 
+      # Removes an existing index, concurrently when supported
+      #
+      # On PostgreSQL this method removes an index concurrently.
+      #
+      # Example:
+      #
+      #     remove_concurrent_index :users, "index_X_by_Y"
+      #
+      # See Rails' `remove_index` for more info on the available arguments.
+      def remove_concurrent_index_by_name(table_name, index_name, options = {})
+        if transaction_open?
+          raise 'remove_concurrent_index_by_name can not be run inside a transaction, ' \
+            'you can disable transactions by calling disable_ddl_transaction! ' \
+            'in the body of your migration class'
+        end
+
+        if supports_drop_index_concurrently?
+          options = options.merge({ algorithm: :concurrently })
+          disable_statement_timeout
+        end
+
+        remove_index(table_name, options.merge({ name: index_name }))
+      end
+
+      # Only available on Postgresql >= 9.2
+      def supports_drop_index_concurrently?
+        return false unless Database.postgresql?
+
+        version = select_one("SELECT current_setting('server_version_num') AS v")['v'].to_i
+
+        version >= 90200
+      end
+
       # Adds a foreign key with only minimal locking on the tables involved.
       #
       # This method only requires minimal locking when using PostgreSQL. When

spec/lib/gitlab/database/migration_helpers_spec.rb

@@ -66,16 +66,23 @@
 
       context 'using PostgreSQL' do
         before do
-          allow(Gitlab::Database).to receive(:postgresql?).and_return(true)
+          allow(model).to receive(:supports_drop_index_concurrently?).and_return(true)
           allow(model).to receive(:disable_statement_timeout)
         end
 
-        it 'removes the index concurrently' do
+        it 'removes the index concurrently by column name' do
           expect(model).to receive(:remove_index).
             with(:users, { algorithm: :concurrently, column: :foo })
 
           model.remove_concurrent_index(:users, :foo)
         end
+
+        it 'removes the index concurrently by index name' do
+          expect(model).to receive(:remove_index).
+            with(:users, { algorithm: :concurrently, name: "index_x_by_y" })
+
+          model.remove_concurrent_index_by_name(:users, "index_x_by_y")
+        end
       end
 
       context 'using MySQL' do