Merge pull request rails#26785 from yahonda/diag26774

Support index.length for MySQL 8.0.0-dmr

Author: rafaelfranca

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -388,7 +388,7 @@ def indexes(table_name, name = nil) #:nodoc:
             end
 
             indexes.last.columns << row[:Column_name]
-            indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part]) if row[:Sub_part]
+            indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
           end
         end