InnoDB memcached Plugin Internals Column Description db_table The name of the  InnoDB  table that stores memcached  values. This is a required value. key_columns The column in the  InnoDB  table that contains lookup key values for  memcached  operations. This is a required value. value_columns The  InnoDB  table columns (one or more) that store  memcached  data. Multiple columns can be specified using the separator character specified in the  innodb_memcached.config_options  table. By default, the separator is a pipe character (“|” ). To specify multiple columns, separate them with the defined separator character. For example:  col1| col2|col3 . This is a required value. flags The  InnoDB  table columns that are used as flags (a user-defined numeric value that is stored and retrieved along with the main value) for  memcached . A flag value can be used as a column specifier for some operations (such as  incr ,  prepend ) if a memcached  value is mapped to multiple columns, so that an operation is performed on a specified column. For example, if you have mapped a value_columns  to three  InnoDB  table columns, and only want the increment operation performed on one columns, use the  flags  column to specify the column. If you do not use the  flags  column, set a value of  0  to indicate that it is unused. cas_column The  InnoDB  table column that stores compare- and-swap (cas) values. The  cas_column  value is related to the way  memcached  hashes requests to different servers and caches data in memory. Because the  InnoDB memcached  plugin is tightly integrated with a single  memcached  daemon, and the in-memory caching mechanism is handled by MySQL and the InnoDB buffer pool, this column is rarely needed. If you do not use this column, set a value of  0  to indicate that it is unused. expire_time_column The  InnoDB  table column that stores expiration values. The  expire_time_column  value is related to the way  memcached  hashes requests to different servers and caches data in memory. Because the InnoDB memcached  plugin is tightly integrated with a single  memcached  daemon, and the in- memory caching mechanism is handled by MySQL and the InnoDB buffer pool, this column is rarely needed. If you do not use this column, set a value of  0  to indicate that the column is unused. The maximum expire time is defined as  INT_MAX32  or 2147483647 seconds (approximately 68 years). unique_idx_name_on_key The name of the index on the key column. It must be a unique index. It can be the primary key or 3386