Add rename_column_safely and rename_column_safely_cleanup migration helpers

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Added `add_foreign_key_safely` method
 - Added `add_null_constraint_safely` and `remove_null_constraint_safely` methods
+- Added `add_column_safely` method
+- Added `backfill_column_safely` method
 - Added `statement_timeout` and `lock_timeout` functionality
 
 ## 0.5.1 (2019-12-17)

lib/strong_migrations.rb

@@ -2,6 +2,7 @@
 require "active_support"
 
 # modules
+require "strong_migrations/util"
 require "strong_migrations/checker"
 require "strong_migrations/database_tasks"
 require "strong_migrations/migration"
@@ -25,28 +26,15 @@ class << self
   self.error_messages = {
     add_column_default:
 "Adding a column with a non-null default causes the entire table to be rewritten.
-Instead, add the column without a default value, then change the default.
+Instead, add the column without a default value, backfill and then change the default.
 
 class %{migration_name} < ActiveRecord::Migration%{migration_suffix}
-  def up
-    %{add_command}
-    %{change_command}
-  end
-
-  def down
-    %{remove_command}
-  end
-end
-
-Then backfill the existing rows in the Rails console or a separate migration with disable_ddl_transaction!.
-
-class Backfill%{migration_name} < ActiveRecord::Migration%{migration_suffix}
   disable_ddl_transaction!
 
   def change
-    %{code}
+    %{command}
   end
-end%{append}",
+end",
 
     add_column_json:
 "There's no equality operator for the json column type, which can

lib/strong_migrations/checker.rb

@@ -1,5 +1,7 @@
 module StrongMigrations
   class Checker
+    include Util
+
     attr_accessor :direction
 
     def initialize(migration)
@@ -81,20 +83,8 @@ def perform(method, *args)
           default = options[:default]
 
           if !default.nil? && !(postgresql? && postgresql_version >= 110000)
-
-            if options[:null] == false
-              options = options.except(:null)
-              append = "
-
-Then add the NOT NULL constraint."
-            end
-
             raise_error :add_column_default,
-              add_command: command_str("add_column", [table, column, type, options.except(:default)]),
-              change_command: command_str("change_column_default", [table, column, default]),
-              remove_command: command_str("remove_column", [table, column]),
-              code: backfill_code(table, column, default),
-              append: append
+              command: command_str("add_column_safely", [table, column, type, options])
           end
 
           if type.to_s == "json" && postgresql?
@@ -186,10 +176,6 @@ def set_timeouts
 
     private
 
-    def connection
-      @migration.connection
-    end
-
     def version
       @migration.version
     end
@@ -202,22 +188,6 @@ def version_safe?
       version && version <= StrongMigrations.start_after
     end
 
-    def postgresql?
-      %w(PostgreSQL PostGIS).include?(connection.adapter_name)
-    end
-
-    def postgresql_version
-      @postgresql_version ||= begin
-        target_version = StrongMigrations.target_postgresql_version
-        if target_version && defined?(Rails) && (Rails.env.development? || Rails.env.test?)
-          # we only need major version right now
-          target_version.to_i * 10000
-        else
-          connection.execute("SHOW server_version_num").first["server_version_num"].to_i
-        end
-      end
-    end
-
     def raise_error(message_key, header: nil, **vars)
       return unless StrongMigrations.check_enabled?(message_key, version: version)
 
@@ -238,7 +208,7 @@ def raise_error(message_key, header: nil, **vars)
 
     def constraint_str(statement, identifiers)
       # not all identifiers are tables, but this method of quoting should be fine
-      code = statement % identifiers.map { |v| connection.quote_table_name(v) }
+      code = quote_identifiers(statement, identifiers)
       "safety_assured do\n      execute '#{code}' \n    end"
     end