PostgreSQL and SQLite, remove varchar limit. [Vladimir Sazhin & Toms Mikoss & Yves Senn]

There is no reason for the PG adapter to have a default limit of 255 on :string
columns. See this snippet from the PG docs:

    Tip: There is no performance difference among these three types, apart
    from increased storage space when using the blank-padded type, and a
    few extra CPU cycles to check the length when storing into a
    length-constrained column. While character(n) has performance
    advantages in some other database systems, there is no such advantage
    in PostgreSQL; in fact character(n) is usually the slowest of the
    three because of its additional storage costs. In most situations text
    or character varying should be used instead.

6 files changed, 11 insertions, 5 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 98fe0fbd62..dce2692b0d 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   PostgreSQL and SQLite string columns no longer have a default limit of 255.
+
+    Fixes #13435, #9153.
+
+    *Vladimir Sazhin*, *Toms Mikoss*, *Yves Senn*
+
 *   Block a few default Class methods as scope name.
 
     For instance, this will raise:
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 9fe8e0497e..3510e4f3b0 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -209,7 +209,7 @@ module ActiveRecord
 
       NATIVE_DATABASE_TYPES = {
         primary_key: "serial primary key",
-        string:      { name: "character varying", limit: 255 },
+        string:      { name: "character varying" },
         text:        { name: "text" },
         integer:     { name: "integer" },
         float:       { name: "float" },
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 6e6a51dab8..cd1f7a16c6 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -63,7 +63,7 @@ module ActiveRecord
 
       NATIVE_DATABASE_TYPES = {
         primary_key:  'INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL',
-        string:       { name: "varchar", limit: 255 },
+        string:       { name: "varchar" },
         text:         { name: "text" },
         integer:      { name: "integer" },
         float:        { name: "float" },
diff --git a/activerecord/test/cases/adapters/postgresql/array_test.rb b/activerecord/test/cases/adapters/postgresql/array_test.rb
index 36ded66998..18dd4a6de8 100644
--- a/activerecord/test/cases/adapters/postgresql/array_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/array_test.rb
@@ -25,7 +25,7 @@ class PostgresqlArrayTest < ActiveRecord::TestCase
 
   def test_column
     assert_equal :string, @column.type
-    assert_equal "character varying(255)", @column.sql_type
+    assert_equal "character varying", @column.sql_type
     assert @column.array
     assert_not @column.text?
     assert_not @column.number?
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index d7ad5ed29f..ad77472333 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -63,7 +63,7 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_column_string_type_and_limit
     assert_equal :string, @first.column_for_attribute("title").type
-    assert_equal 255, @first.column_for_attribute("title").limit
+    assert_equal 250, @first.column_for_attribute("title").limit
   end
 
   def test_column_null_not_null
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index a9c4980283..d79cce8cca 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -673,7 +673,7 @@ ActiveRecord::Schema.define do
   end
 
   create_table :topics, force: true do |t|
-    t.string   :title
+    t.string   :title, limit: 250
     t.string   :author_name
     t.string   :author_email_address
     if mysql_56?