Allow changing text and blob size without giving the `limit` option

In MySQL, the text column size is 65,535 bytes by default (1 GiB in
PostgreSQL). It is sometimes too short when people want to use a text
column, so they sometimes change the text size to mediumtext (16 MiB) or
longtext (4 GiB) by giving the `limit` option.

Unlike MySQL, PostgreSQL doesn't allow the `limit` option for a text
column (raises ERROR: type modifier is not allowed for type "text").
So `limit: 4294967295` (longtext) couldn't be used in Action Text.

I've allowed changing text and blob size without giving the `limit`
option, it prevents that migration failure on PostgreSQL.

actionmailbox/db/migrate/20180917164000_create_action_mailbox_tables.rb

@@ -5,11 +5,7 @@ class CreateActionMailboxTables < ActiveRecord::Migration[6.0]
       t.string  :message_id, null: false
       t.string  :message_checksum, null: false
 
-      if supports_datetime_with_precision?
-        t.timestamps precision: 6
-      else
-        t.timestamps
-      end
+      t.timestamps
 
       t.index [ :message_id, :message_checksum ], name: "index_action_mailbox_inbound_emails_uniqueness", unique: true
     end

actiontext/db/migrate/20180528164100_create_action_text_tables.rb

@@ -2,7 +2,7 @@ class CreateActionTextTables < ActiveRecord::Migration[6.0]
   def change
     create_table :action_text_rich_texts do |t|
       t.string     :name, null: false
-      t.text       :body, limit: 16777215
+      t.text       :body, size: :long
       t.references :record, null: false, polymorphic: true, index: false
 
       t.timestamps

actiontext/test/dummy/db/migrate/20180528164100_create_action_text_tables.rb

@@ -2,11 +2,10 @@ class CreateActionTextTables < ActiveRecord::Migration[6.0]
   def change
     create_table :action_text_rich_texts do |t|
       t.string     :name, null: false
-      t.text       :body, limit: 16777215
+      t.text       :body, size: :long
       t.references :record, null: false, polymorphic: true, index: false
 
-      t.datetime :created_at, null: false
-      t.datetime :updated_at, null: false
+      t.timestamps
 
       t.index [ :record_type, :record_id, :name ], name: "index_action_text_rich_texts_uniqueness", unique: true
     end

actiontext/test/dummy/db/schema.rb

@@ -14,7 +14,7 @@ ActiveRecord::Schema.define(version: 2018_10_03_185713) do
 
   create_table "action_text_rich_texts", force: :cascade do |t|
     t.string "name", null: false
-    t.text "body", limit: 16777215
+    t.text "body"
     t.string "record_type", null: false
     t.integer "record_id", null: false
     t.datetime "created_at", precision: 6, null: false

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   MySQL: Support `:size` option to change text and blob size.
+
+    *Ryuta Kamizono*
+
 *   Make `t.timestamps` with precision by default.
 
     *Ryuta Kamizono*

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -29,7 +29,7 @@ module ActiveRecord
       NATIVE_DATABASE_TYPES = {
         primary_key: "bigint auto_increment PRIMARY KEY",
         string:      { name: "varchar", limit: 255 },
-        text:        { name: "text", limit: 65535 },
+        text:        { name: "text" },
         integer:     { name: "int", limit: 4 },
         float:       { name: "float", limit: 24 },
         decimal:     { name: "decimal" },
@@ -37,7 +37,8 @@ module ActiveRecord
         timestamp:   { name: "timestamp" },
         time:        { name: "time" },
         date:        { name: "date" },
-        binary:      { name: "blob", limit: 65535 },
+        binary:      { name: "blob" },
+        blob:        { name: "blob" },
         boolean:     { name: "tinyint", limit: 1 },
         json:        { name: "json" },
       }

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

@@ -56,6 +56,16 @@ module ActiveRecord
           case type
           when :virtual
             type = options[:type]
+          when :text, :blob, :binary
+            case (size = options[:size])&.to_s
+            when "tiny", "medium", "long"
+              sql_type = @conn.native_database_types[type][:name]
+              type = "#{size}#{sql_type}"
+            else
+              raise ArgumentError, <<~MSG unless size.nil?
+                #{size.inspect} is invalid :size value. Only :tiny, :medium, and :long are allowed.
+              MSG
+            end
           when :primary_key
             type = :integer
             options[:limit] ||= 8

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

@@ -10,6 +10,10 @@ module ActiveRecord
             spec[:unsigned] = "true" if column.unsigned?
             spec[:auto_increment] = "true" if column.auto_increment?
 
+            if /\A(?<size>tiny|medium|long)(?:text|blob)/ =~ column.sql_type
+              spec = { size: size.to_sym.inspect }.merge!(spec)
+            end
+
             if @connection.supports_virtual_columns? && column.virtual?
               spec[:as] = extract_expression_for_virtual_column(column)
               spec[:stored] = "true" if /\b(?:STORED|PERSISTENT)\b/.match?(column.extra)
@@ -37,13 +41,15 @@ module ActiveRecord
             case column.sql_type
             when /\Atimestamp\b/
               :timestamp
-            when "tinyblob"
-              :blob
             else
               super
             end
           end
 
+          def schema_limit(column)
+            super unless /\A(?:tiny|medium|long)?(?:text|blob)/.match?(column.sql_type)
+          end
+
           def schema_precision(column)
             super unless /\A(?:date)?time(?:stamp)?\b/.match?(column.sql_type) && column.precision == 0
           end

activerecord/test/cases/migration_test.rb

@@ -626,6 +626,18 @@ class MigrationTest < ActiveRecord::TestCase
     ensure
       Person.connection.drop_table :test_text_limits, if_exists: true
     end
+
+    def test_invalid_text_size_should_raise
+      e = assert_raise(ArgumentError) do
+        Person.connection.create_table :test_text_sizes, force: true do |t|
+          t.text :bigtext, size: 0xfffffffff
+        end
+      end
+
+      assert_match(/#{0xfffffffff} is invalid :size value\. Only :tiny, :medium, and :long are allowed\./, e.message)
+    ensure
+      Person.connection.drop_table :test_text_sizes, if_exists: true
+    end
   end
 
   if ActiveRecord::Base.connection.supports_advisory_locks?

activerecord/test/cases/schema_dumper_test.rb

@@ -245,25 +245,31 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
   if current_adapter?(:Mysql2Adapter)
     def test_schema_dump_includes_length_for_mysql_binary_fields
-      output = standard_dump
+      output = dump_table_schema "binary_fields"
       assert_match %r{t\.binary\s+"var_binary",\s+limit: 255$}, output
       assert_match %r{t\.binary\s+"var_binary_large",\s+limit: 4095$}, output
     end
 
     def test_schema_dump_includes_length_for_mysql_blob_and_text_fields
-      output = standard_dump
-      assert_match %r{t\.blob\s+"tiny_blob",\s+limit: 255$}, output
+      output = dump_table_schema "binary_fields"
+      assert_match %r{t\.binary\s+"tiny_blob",\s+size: :tiny$}, output
       assert_match %r{t\.binary\s+"normal_blob"$}, output
-      assert_match %r{t\.binary\s+"medium_blob",\s+limit: 16777215$}, output
-      assert_match %r{t\.binary\s+"long_blob",\s+limit: 4294967295$}, output
-      assert_match %r{t\.text\s+"tiny_text",\s+limit: 255$}, output
+      assert_match %r{t\.binary\s+"medium_blob",\s+size: :medium$}, output
+      assert_match %r{t\.binary\s+"long_blob",\s+size: :long$}, output
+      assert_match %r{t\.text\s+"tiny_text",\s+size: :tiny$}, output
       assert_match %r{t\.text\s+"normal_text"$}, output
-      assert_match %r{t\.text\s+"medium_text",\s+limit: 16777215$}, output
-      assert_match %r{t\.text\s+"long_text",\s+limit: 4294967295$}, output
+      assert_match %r{t\.text\s+"medium_text",\s+size: :medium$}, output
+      assert_match %r{t\.text\s+"long_text",\s+size: :long$}, output
+      assert_match %r{t\.binary\s+"tiny_blob_2",\s+size: :tiny$}, output
+      assert_match %r{t\.binary\s+"medium_blob_2",\s+size: :medium$}, output
+      assert_match %r{t\.binary\s+"long_blob_2",\s+size: :long$}, output
+      assert_match %r{t\.text\s+"tiny_text_2",\s+size: :tiny$}, output
+      assert_match %r{t\.text\s+"medium_text_2",\s+size: :medium$}, output
+      assert_match %r{t\.text\s+"long_text_2",\s+size: :long$}, output
     end
 
     def test_schema_does_not_include_limit_for_emulated_mysql_boolean_fields
-      output = standard_dump
+      output = dump_table_schema "booleans"
       assert_no_match %r{t\.boolean\s+"has_fun",.+limit: 1}, output
     end
 

activerecord/test/schema/mysql2_specific_schema.rb

@@ -27,6 +27,7 @@ ActiveRecord::Schema.define do
   create_table :binary_fields, force: true do |t|
     t.binary :var_binary, limit: 255
     t.binary :var_binary_large, limit: 4095
+
     t.tinyblob   :tiny_blob
     t.blob       :normal_blob
     t.mediumblob :medium_blob
@@ -36,6 +37,13 @@ ActiveRecord::Schema.define do
     t.mediumtext :medium_text
     t.longtext   :long_text
 
+    t.binary :tiny_blob_2, size: :tiny
+    t.binary :medium_blob_2, size: :medium
+    t.binary :long_blob_2, size: :long
+    t.text :tiny_text_2, size: :tiny
+    t.text :medium_text_2, size: :medium
+    t.text :long_text_2, size: :long
+
     t.index :var_binary
   end