Only use LOWER for mysql case insensitive uniqueness check when column has a case sensitive collation.

5 files changed, 33 insertions, 10 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 443e61b527..4c3a8f7233 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -238,6 +238,10 @@ module ActiveRecord
         node
       end
 
+      def case_insensitive_comparison(table, attribute, column, value)
+        table[attribute].lower.eq(table.lower(value))
+      end
+
       def current_savepoint_name
         "active_record_#{open_transactions}"
       end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 4b7c74e0b8..dd573ba569 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -4,6 +4,13 @@ module ActiveRecord
   module ConnectionAdapters
     class AbstractMysqlAdapter < AbstractAdapter
       class Column < ConnectionAdapters::Column # :nodoc:
+        attr_reader :collation
+
+        def initialize(name, default, sql_type = nil, null = true, collation = nil)
+          super(name, default, sql_type, null)
+          @collation = collation
+        end
+
         def extract_default(default)
           if sql_type =~ /blob/i || type == :text
             if default.blank?
@@ -28,6 +35,10 @@ module ActiveRecord
           raise NotImplementedError
         end
 
+        def case_sensitive?
+          collation && !collation.match(/_ci$/)
+        end
+
         private
 
         def simplified_type(field_type)
@@ -157,8 +168,8 @@ module ActiveRecord
       end
 
       # Overridden by the adapters to instantiate their specific Column type.
-      def new_column(field, default, type, null) # :nodoc:
-        Column.new(field, default, type, null)
+      def new_column(field, default, type, null, collation) # :nodoc:
+        Column.new(field, default, type, null, collation)
       end
 
       # Must return the Mysql error number from the exception, if the exception has an
@@ -393,10 +404,10 @@ module ActiveRecord
 
       # Returns an array of +Column+ objects for the table specified by +table_name+.
       def columns(table_name, name = nil)#:nodoc:
-        sql = "SHOW FIELDS FROM #{quote_table_name(table_name)}"
+        sql = "SHOW FULL FIELDS FROM #{quote_table_name(table_name)}"
         execute_and_free(sql, 'SCHEMA') do |result|
           each_hash(result).map do |field|
-            new_column(field[:Field], field[:Default], field[:Type], field[:Null] == "YES")
+            new_column(field[:Field], field[:Default], field[:Type], field[:Null] == "YES", field[:Collation])
           end
         end
       end
@@ -501,6 +512,14 @@ module ActiveRecord
         Arel::Nodes::Bin.new(node)
       end
 
+      def case_insensitive_comparison(table, attribute, column, value)
+        if column.case_sensitive?
+          super
+        else
+          table[attribute].eq(value)
+        end
+      end
+
       def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
         where_sql
       end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 8b574518e5..971f3c35f3 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -47,8 +47,8 @@ module ActiveRecord
         end
       end
 
-      def new_column(field, default, type, null) # :nodoc:
-        Column.new(field, default, type, null)
+      def new_column(field, default, type, null, collation) # :nodoc:
+        Column.new(field, default, type, null, collation)
       end
 
       def error_number(exception)
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index a1824fe396..f092edecda 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -150,8 +150,8 @@ module ActiveRecord
         end
       end
 
-      def new_column(field, default, type, null) # :nodoc:
-        Column.new(field, default, type, null)
+      def new_column(field, default, type, null, collation) # :nodoc:
+        Column.new(field, default, type, null, collation)
       end
 
       def error_number(exception) # :nodoc:
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 484b1d369b..2e2ea8c42b 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -57,8 +57,8 @@ module ActiveRecord
         value = column.limit ? value.to_s.mb_chars[0, column.limit] : value.to_s if column.text?
 
         if !options[:case_sensitive] && value && column.text?
-          # will use SQL LOWER function before comparison
-          relation = table[attribute].lower.eq(table.lower(value))
+          # will use SQL LOWER function before comparison, unless it detects a case insensitive collation
+          relation = klass.connection.case_insensitive_comparison(table, attribute, column, value)
         else
           value    = klass.connection.case_sensitive_modifier(value)
           relation = table[attribute].eq(value)