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sets limit 191 for schema_migrations#version in mysql2 if the encodin…

…g is "utf8mb4"

Please, see rationale in the included CHANGELOG patch.
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commit 8744632fb5649cf26cdcd1518a3554ece95a401b 1 parent b365354
Xavier Noria fxn authored
15 activerecord/CHANGELOG.md
View
@@ -1,5 +1,20 @@
## Rails 4.0.0 (unreleased) ##
+* The length of the `version` column in the `schema_migrations` table
+ created by the `mysql2` adapter is 191 if the encoding is "utf8mb4".
+
+ The "utf8" encoding in MySQL has support for a maximum of 3 bytes per character,
+ and only contains characters from the BMP. The recently added
+ [utf8mb4](http://dev.mysql.com/doc/refman/5.5/en/charset-unicode-utf8mb4.html)
+ encoding extends the support to four bytes. As of this writing, said encoding
+ is supported in the betas of the `mysql2` gem.
+
+ Setting the encoding to "utf8mb4" has
+ [a few implications](http://dev.mysql.com/doc/refman/5.5/en/charset-unicode-upgrading.html).
+ This change addresses the max length for indexes, which is 191 instead of 255.
+
+ *Xavier Noria*
+
* Counter caches on associations will now stay valid when attributes are
updated (not just when records are created or destroyed), for example,
when calling `update_attributes`. The following code now works:
9 activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
View
@@ -38,6 +38,15 @@ def initialize(connection, logger, connection_options, config)
configure_connection
end
+ MAX_INDEX_LENGTH_FOR_UTF8MB4 = 191
+ def initialize_schema_migrations_table
+ if @config[:encoding] == 'utf8mb4'
+ ActiveRecord::SchemaMigration.create_table(MAX_INDEX_LENGTH_FOR_UTF8MB4)
+ else
+ ActiveRecord::SchemaMigration.create_table
+ end
+ end
+
def supports_explain?
true
end
13 activerecord/lib/active_record/schema_migration.rb
View
@@ -13,18 +13,21 @@ def self.index_name
"#{Base.table_name_prefix}unique_schema_migrations#{Base.table_name_suffix}"
end
- def self.create_table
+ def self.create_table(limit=nil)
unless connection.table_exists?(table_name)
- connection.create_table(table_name, :id => false) do |t|
- t.column :version, :string, :null => false
+ version_options = {null: false}
+ version_options[:limit] = limit if limit
+
+ connection.create_table(table_name, id: false) do |t|
+ t.column :version, :string, version_options
end
- connection.add_index table_name, :version, :unique => true, :name => index_name
+ connection.add_index table_name, :version, unique: true, name: index_name
end
end
def self.drop_table
if connection.table_exists?(table_name)
- connection.remove_index table_name, :name => index_name
+ connection.remove_index table_name, name: index_name
connection.drop_table(table_name)
end
end
26 activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
View
@@ -0,0 +1,26 @@
+require "cases/helper"
+
+module ActiveRecord
+ module ConnectionAdapters
+ class Mysql2Adapter
+ class SchemaMigrationsTest < ActiveRecord::TestCase
+ def test_initializes_schema_migrations_for_encoding_utf8mb4
+ conn = ActiveRecord::Base.connection
+
+ smtn = ActiveRecord::Migrator.schema_migrations_table_name
+ conn.drop_table(smtn) if conn.table_exists?(smtn)
+
+ config = conn.instance_variable_get(:@config)
+ original_encoding = config[:encoding]
+
+ config[:encoding] = 'utf8mb4'
+ conn.initialize_schema_migrations_table
+
+ assert conn.column_exists?(smtn, :version, :string, limit: Mysql2Adapter::MAX_INDEX_LENGTH_FOR_UTF8MB4)
+ ensure
+ config[:encoding] = original_encoding
+ end
+ end
+ end
+ end
+end
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