宏HASH_GET_FIRST

/*******************************************************************//**
Gets the first struct in a hash chain, NULL if none. */

#define HASH_GET_FIRST(TABLE, HASH_VAL)\
    (hash_get_nth_cell(TABLE, HASH_VAL)->node)

/************************************************************//**
Gets the nth cell in a hash table.
@return    pointer to cell */
UNIV_INLINE
hash_cell_t*
hash_get_nth_cell(
/*==============*/
    hash_table_t*    table,    /*!< in: hash table */
    ulint        n)    /*!< in: cell index */
{
    ut_ad(table);
    ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
    ut_ad(n < table->n_cells);

    return(table->array + n);
}