Schema dumping support for PostgreSQL interval type

Closes #27979

activerecord/CHANGELOG.md

+*   PostgreSQL: schema dumping support for PostgreSQL interval type.
+
+    *Ryuta Kamizono*
+
 *   Deprecate `supports_primary_key?` on connection adapters since it's
     been long unused and unsupported.
 

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

@@ -1070,7 +1070,7 @@ def type_to_sql(type, limit: nil, precision: nil, scale: nil, **) # :nodoc:
               raise ArgumentError, "Error adding decimal column: precision cannot be empty if scale is specified"
             end
 
-          elsif [:datetime, :time].include?(type) && precision ||= native[:precision]
+          elsif [:datetime, :time, :interval].include?(type) && precision ||= native[:precision]
             if (0..6) === precision
               column_type_sql << "(#{precision})"
             else

activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb

@@ -5,8 +5,9 @@ module OID # :nodoc:
         class SpecializedString < Type::String # :nodoc:
           attr_reader :type
 
-          def initialize(type)
+          def initialize(type, **options)
             @type = type
+            super(options)
           end
         end
       end

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

@@ -88,6 +88,10 @@ def inet(*args, **options)
           args.each { |name| column(name, :inet, options) }
         end
 
+        def interval(*args, **options)
+          args.each { |name| column(name, :interval, options) }
+        end
+
         def int4range(*args, **options)
           args.each { |name| column(name, :int4range, options) }
         end

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -109,6 +109,7 @@ class PostgreSQLAdapter < AbstractAdapter
         bit:         { name: "bit" },
         bit_varying: { name: "bit varying" },
         money:       { name: "money" },
+        interval:    { name: "interval" },
       }
 
       OID = PostgreSQL::OID #:nodoc:
@@ -486,8 +487,10 @@ def initialize_type_map(m)
           m.register_type "polygon", OID::SpecializedString.new(:polygon)
           m.register_type "circle", OID::SpecializedString.new(:circle)
 
-          # FIXME: why are we keeping these types as strings?
-          m.alias_type "interval", "varchar"
+          m.register_type "interval" do |_, _, sql_type|
+            precision = extract_precision(sql_type)
+            OID::SpecializedString.new(:interval, precision: precision)
+          end
 
           register_class_with_precision m, "time", Type::Time
           register_class_with_precision m, "timestamp", OID::DateTime

activerecord/test/cases/adapters/postgresql/datatype_test.rb

@@ -28,8 +28,8 @@ def setup
   end
 
   def test_data_type_of_time_types
-    assert_equal :string, @first_time.column_for_attribute(:time_interval).type
-    assert_equal :string, @first_time.column_for_attribute(:scaled_time_interval).type
+    assert_equal :interval, @first_time.column_for_attribute(:time_interval).type
+    assert_equal :interval, @first_time.column_for_attribute(:scaled_time_interval).type
   end
 
   def test_data_type_of_oid_types

activerecord/test/cases/schema_dumper_test.rb

@@ -261,25 +261,31 @@ def test_schema_dump_includes_decimal_options
 
   if current_adapter?(:PostgreSQLAdapter)
     def test_schema_dump_includes_bigint_default
-      output = standard_dump
+      output = dump_table_schema "defaults"
       assert_match %r{t\.bigint\s+"bigint_default",\s+default: 0}, output
     end
 
     def test_schema_dump_includes_limit_on_array_type
-      output = standard_dump
+      output = dump_table_schema "bigint_array"
       assert_match %r{t\.bigint\s+"big_int_data_points\",\s+array: true}, output
     end
 
     def test_schema_dump_allows_array_of_decimal_defaults
-      output = standard_dump
+      output = dump_table_schema "bigint_array"
       assert_match %r{t\.decimal\s+"decimal_array_default",\s+default: \["1.23", "3.45"\],\s+array: true}, output
     end
 
     def test_schema_dump_expression_indices
-      index_definition = standard_dump.split(/\n/).grep(/t\.index.*company_expression_index/).first.strip
+      index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*company_expression_index/).first.strip
       assert_equal 't.index "lower((name)::text)", name: "company_expression_index", using: :btree', index_definition
     end
 
+    def test_schema_dump_interval_type
+      output = dump_table_schema "postgresql_times"
+      assert_match %r{t\.interval\s+"time_interval"$}, output
+      assert_match %r{t\.interval\s+"scaled_time_interval",\s+precision: 6$}, output
+    end
+
     if ActiveRecord::Base.connection.supports_extensions?
       def test_schema_dump_includes_extensions
         connection = ActiveRecord::Base.connection

activerecord/test/schema/postgresql_specific_schema.rb

@@ -23,12 +23,17 @@
     t.string :char2, limit: 50, default: "a varchar field"
     t.text :char3, default: "a text field"
     t.bigint :bigint_default, default: -> { "0::bigint" }
-    t.text :multiline_default, default: '--- []
+    t.text :multiline_default, default: "--- []
 
-'
+"
   end
 
-  %w(postgresql_times postgresql_oids postgresql_timestamp_with_zones
+  create_table :postgresql_times, force: true do |t|
+    t.interval :time_interval
+    t.interval :scaled_time_interval, precision: 6
+  end
+
+  %w(postgresql_oids postgresql_timestamp_with_zones
       postgresql_partitioned_table postgresql_partitioned_table_parent).each do |table_name|
     drop_table table_name, if_exists: true
   end
@@ -44,14 +49,6 @@
     execute "SELECT setval('#{seq_name}', 100)"
   end
 
-  execute <<_SQL
-  CREATE TABLE postgresql_times (
-    id SERIAL PRIMARY KEY,
-    time_interval INTERVAL,
-    scaled_time_interval INTERVAL(6)
-  );
-_SQL
-
   execute <<_SQL
   CREATE TABLE postgresql_oids (
     id SERIAL PRIMARY KEY,