# Db::set_h_ffactor |

`

###

    #include <db_cxx.h>

    int
    Db::set_h_ffactor(u_int32_t h_ffactor);

# Description

Set the desired density within the hash table.

The density is an approximation of the number of keys allowed to accumulate in any one bucket, determining when the hash table grows or shrinks. If you know the average sizes of the keys and data in your dataset, setting the fill factor can enhance performance. A reasonable rule computing fill factor is to set it to:

>     (pagesize - 32) / (average_key_size + average_data_size + 8)

If no value is specified, the fill factor will be selected dynamically as pages are filled.

The Db::set_h_ffactor interface may only be used to configure Berkeley DB before the Db::open interface is called.

The Db::set_h_ffactor method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

# Errors

EINVAL
  An invalid flag value or parameter was specified.

  Called after Db::open was called.

### Class

Db

# See Also

Db::close, Db::cursor, Db::del, Db::err, Db::fd, Db::get, Db::get_byteswapped, Db::get_type, Db::join, Db::key_range, Db::open, Db::put, Db::remove, Db::set_bt_compare, Db::set_bt_minkey, Db::set_bt_prefix, Db::set_cachesize, Db::set_dup_compare, Db::set_errcall, Db::set_errfile, Db::set_errpfx, Db::set_flags, Db::set_h_ffactor, Db::set_h_hash, Db::set_h_nelem, Db::set_lorder, Db::set_malloc, Db::set_pagesize, Db::set_paniccall, Db::set_q_extentsize, Db::set_realloc, Db::set_re_delim, Db::set_re_len, Db::set_re_pad, Db::set_re_source, Db::stat, Db::sync, Db::upgrade and Db::verify.`

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