Merge branch '32851-fix-postgres-9-1' into 'master'

Resolve "GitLab 9.0 to 9.2 is incompatible with PostgreSQL 9.1"

See merge request !11709

1 files changed, 34 insertions, 1 deletions

diff --git a/lib/gitlab/database/migration_helpers.rb b/lib/gitlab/database/migration_helpers.rb
index e76c9abbe04..a412bb6dbd2 100644
--- a/lib/gitlab/database/migration_helpers.rb
+++ b/lib/gitlab/database/migration_helpers.rb
@@ -42,7 +42,7 @@ module Gitlab
             '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 @@ module Gitlab
         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