Fixed MariaDB default function

Dont test default function on MySQL where it is unsupported and default expect default function instead of default value

Simplified test - dont repeat last test

Removed cache of create table SQL - it messes up when tables change, and it should only be called when a default is set and the other cases arent true anyway

Test if string first (starts with single quote) because default_type does a SQL lookup and is more expensive

Fixed tests: Postgres uses a different named method for generating UUID's

Skip check if column default is a function when it starts with a number to reduce the number of queries done

Added note in CHANGELOG.md

activerecord/CHANGELOG.md

@@ -1,3 +1,11 @@
+*   Fixed MariaDB default function support.
+
+    Defaults would be written wrong in "db/schema.rb" and not work correctly
+    if using `db:schema:load`. Further more the function name would be
+    added as string content when saving new records.
+
+    *kaspernj*
+
 *   Add `active_record.destroy_association_async_batch_size` configuration
 
     This allows applications to specify the maximum number of records that will

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

@@ -158,7 +158,27 @@ module ActiveRecord
             MySQL::TableDefinition.new(self, name, **options)
           end
 
+          def default_type(table_name, field_name)
+            match = create_table_sql(table_name).match(/`#{field_name}` (.+) DEFAULT ('|\d+|[A-z]+)/)
+            default_pre = match[2] if match
+
+            if default_pre == "'"
+              :string
+            elsif default_pre&.match?(/^\d+$/)
+              :integer
+            elsif default_pre&.match?(/^[A-z]+$/)
+              :function
+            end
+          end
+
+          def create_table_sql(table_name)
+            execute_and_free("SHOW CREATE TABLE #{quote_table_name(table_name)}") do |result|
+              result.first[1]
+            end
+          end
+
           def new_column_from_field(table_name, field)
+            field_name = field.fetch(:Field)
             type_metadata = fetch_type_metadata(field[:Type], field[:Extra])
             default, default_function = field[:Default], nil
 
@@ -168,9 +188,13 @@ module ActiveRecord
             elsif type_metadata.extra == "DEFAULT_GENERATED"
               default = +"(#{default})" unless default.start_with?("(")
               default, default_function = nil, default
-            elsif type_metadata.type == :text && default
+            elsif type_metadata.type == :text && default&.start_with?("'")
               # strip and unescape quotes
               default = default[1...-1].gsub("\\'", "'")
+            elsif default&.match?(/\A\d/)
+              # Its a number so we can skip the query to check if it is a function
+            elsif default && default_type(table_name, field_name) == :function
+              default, default_function = nil, default
             end
 
             MySQL::Column.new(

activerecord/test/cases/migration_test.rb

@@ -1347,6 +1347,32 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
       assert_equal "This is a comment", column(:birthdate).comment
     end
 
+    if supports_text_column_with_default?
+      def test_default_functions_on_columns
+        with_bulk_change_table do |t|
+          if current_adapter?(:PostgreSQLAdapter)
+            t.string :name, default: -> { "gen_random_uuid()" }
+          else
+            t.string :name, default: -> { "UUID()" }
+          end
+        end
+
+        assert_nil column(:name).default
+
+        if current_adapter?(:PostgreSQLAdapter)
+          assert_equal "gen_random_uuid()", column(:name).default_function
+          Person.connection.execute("INSERT INTO delete_me DEFAULT VALUES")
+          person_data = Person.connection.execute("SELECT * FROM delete_me ORDER BY id DESC").to_a.first
+        else
+          assert_equal "uuid()", column(:name).default_function
+          Person.connection.execute("INSERT INTO delete_me () VALUES ()")
+          person_data = Person.connection.execute("SELECT * FROM delete_me ORDER BY id DESC").to_a(as: :hash).first
+        end
+
+        assert_match(/\A(.+)-(.+)-(.+)-(.+)\Z/, person_data.fetch("name"))
+      end
+    end
+
     if current_adapter?(:Mysql2Adapter)
       def test_updating_auto_increment
         with_bulk_change_table do |t|

activerecord/test/cases/schema_dumper_test.rb

@@ -825,7 +825,16 @@ class SchemaDumperDefaultsTest < ActiveRecord::TestCase
       t.datetime :datetime_with_default, default: "2014-06-05 07:17:04"
       t.time     :time_with_default,     default: "07:17:04"
       t.decimal  :decimal_with_default,  default: "1234567890.0123456789", precision: 20, scale: 10
-      t.text :text_with_default, default: "John' Doe" if supports_text_column_with_default?
+
+      if supports_text_column_with_default?
+        t.text :text_with_default, default: "John' Doe"
+
+        if current_adapter?(:PostgreSQLAdapter)
+          t.text :uuid, default: -> { "gen_random_uuid()" }
+        else
+          t.text :uuid, default: -> { "uuid()" }
+        end
+      end
     end
 
     if current_adapter?(:PostgreSQLAdapter)
@@ -864,6 +873,12 @@ class SchemaDumperDefaultsTest < ActiveRecord::TestCase
     output = dump_table_schema("dump_defaults")
 
     assert_match %r{t\.text\s+"text_with_default",.*?default: "John' Doe"}, output
+
+    if current_adapter?(:PostgreSQLAdapter)
+      assert_match %r{t\.text\s+"uuid",.*?default: -> \{ "gen_random_uuid\(\)" \}}, output
+    else
+      assert_match %r{t\.text\s+"uuid",.*?default: -> \{ "uuid\(\)" \}}, output
+    end
   end if supports_text_column_with_default?
 
   def test_schema_dump_with_column_infinity_default