Add bulk alter support for PostgreSQL

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -364,6 +364,31 @@ module ActiveRecord
           SQL
         end
 
+        def bulk_change_table(table_name, operations)
+          sql_fragments = []
+          non_combinable_operations = []
+
+          operations.each do |command, args|
+            table, arguments = args.shift, args
+            method = :"#{command}_for_alter"
+
+            if respond_to?(method, true)
+              sqls, procs = Array(send(method, table, *arguments)).partition { |v| v.is_a?(String) }
+              sql_fragments << sqls
+              non_combinable_operations << procs if procs.present?
+            else
+              execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
+              non_combinable_operations.each(&:call)
+              sql_fragments = []
+              non_combinable_operations = []
+              send(command, table, *arguments)
+            end
+          end
+
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
+          non_combinable_operations.each(&:call)
+        end
+
         # Renames a table.
         # Also renames a table's primary key sequence if the sequence name exists and
         # matches the Active Record default.
@@ -394,7 +419,7 @@ module ActiveRecord
 
         def change_column(table_name, column_name, type, options = {}) #:nodoc:
           clear_cache!
-          sqls, procs = change_column_for_alter(table_name, column_name, type, options)
+          sqls, procs = Array(change_column_for_alter(table_name, column_name, type, options)).partition { |v| v.is_a?(String) }
           execute "ALTER TABLE #{quote_table_name(table_name)} #{sqls.join(", ")}"
           procs.each(&:call)
         end
@@ -665,12 +690,10 @@ module ActiveRecord
 
           def change_column_for_alter(table_name, column_name, type, options = {})
             sqls = [change_column_sql(table_name, column_name, type, options)]
-            procs = []
             sqls << change_column_default_for_alter(table_name, column_name, options[:default]) if options.key?(:default)
             sqls << change_column_null_for_alter(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
-            procs << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
-
-            [sqls, procs]
+            sqls << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
+            sqls
           end
 
 
@@ -694,6 +717,14 @@ module ActiveRecord
             "ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL"
           end
 
+          def add_timestamps_for_alter(table_name, options = {})
+            [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
+          end
+
+          def remove_timestamps_for_alter(table_name, options = {})
+            [remove_column_for_alter(table_name, :updated_at), remove_column_for_alter(table_name, :created_at)]
+          end
+
           def add_index_opclass(quoted_columns, **options)
             opclasses = options_for_index_columns(options[:opclass])
             quoted_columns.each do |name, column|

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -122,6 +122,10 @@ module ActiveRecord
       include PostgreSQL::SchemaStatements
       include PostgreSQL::DatabaseStatements
 
+      def supports_bulk_alter?
+        true
+      end
+
       def supports_index_sort_order?
         true
       end

activerecord/test/cases/migration_test.rb

@@ -801,8 +801,15 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
         t.integer :age
       end
 
-      # Adding an index fires a query every time to check if an index already exists or not
-      assert_queries(3) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "PostgreSQLAdapter" => 2,
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count) do
         with_bulk_change_table do |t|
           t.index :username, unique: true, name: :awesome_username_index
           t.index [:name, :age]
@@ -826,7 +833,15 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
 
       assert index(:index_delete_me_on_name)
 
-      assert_queries(3) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "PostgreSQLAdapter" => 2,
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count) do
         with_bulk_change_table do |t|
           t.remove_index :name
           t.index :name, name: :new_name_index, unique: true
@@ -848,10 +863,15 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
       assert ! column(:name).default
       assert_equal :date, column(:birthdate).type
 
-      # One query for columns (delete_me table)
-      # One query for primary key (delete_me table)
-      # One query to do the bulk change
-      assert_queries(3, ignore_none: true) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # one query for columns, one query for primary key, one query to do the bulk change
+        "PostgreSQLAdapter" => 2, # one query for columns, one for bulk change
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count, ignore_none: true) do
         with_bulk_change_table do |t|
           t.change :name, :string, default: "NONAME"
           t.change :birthdate, :datetime

activerecord/test/cases/test_case.rb

@@ -112,7 +112,7 @@ module ActiveRecord
     # instead examining the SQL content.
     oracle_ignored     = [/^select .*nextval/i, /^SAVEPOINT/, /^ROLLBACK TO/, /^\s*select .* from all_triggers/im, /^\s*select .* from all_constraints/im, /^\s*select .* from all_tab_cols/im, /^\s*select .* from all_sequences/im]
     mysql_ignored      = [/^SHOW FULL TABLES/i, /^SHOW FULL FIELDS/, /^SHOW CREATE TABLE /i, /^SHOW VARIABLES /, /^\s*SELECT (?:column_name|table_name)\b.*\bFROM information_schema\.(?:key_column_usage|tables)\b/im]
-    postgresql_ignored = [/^\s*select\b.*\bfrom\b.*pg_namespace\b/im, /^\s*select tablename\b.*from pg_tables\b/im, /^\s*select\b.*\battname\b.*\bfrom\b.*\bpg_attribute\b/im, /^SHOW search_path/i]
+    postgresql_ignored = [/^\s*select\b.*\bfrom\b.*pg_namespace\b/im, /^\s*select tablename\b.*from pg_tables\b/im, /^\s*select\b.*\battname\b.*\bfrom\b.*\bpg_attribute\b/im, /^SHOW search_path/i, /^\s*SELECT\b.*::regtype::oid\b/im]
     sqlite3_ignored =    [/^\s*SELECT name\b.*\bFROM sqlite_master/im, /^\s*SELECT sql\b.*\bFROM sqlite_master/im]
 
     [oracle_ignored, mysql_ignored, postgresql_ignored, sqlite3_ignored].each do |db_ignored_sql|