typedef struct st_key {

  uint    key_length;            /* Tot length of key */

  ulong flags;                          /* dupp key and pack flags */

  uint    key_parts;            /* How many key_parts */

  uint  extra_length;

  uint    usable_key_parts;        /* Should normally be = key_parts */

  uint  block_size;

  enum  ha_key_alg algorithm;

  /*

    Note that parser is used when the table is opened for use, and

    parser_name is used when the table is being created.

  */

  union

  {

    plugin_ref parser;                  /* Fulltext [pre]parser */

    LEX_STRING *parser_name;            /* Fulltext [pre]parser name */

  };

  KEY_PART_INFO *key_part;

  char    *name;                /* Name of key */

  /*

    Array of AVG(#records with the same field value) for 1st ... Nth key part.

    0 means 'not known'.

    For temporary heap tables this member is NULL.

  */

  ulong *rec_per_key;

  union {

    int  bdb_return_if_eq;

  } handler;

  TABLE *table;

  LEX_STRING comment;

} KEY;