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
data set, setting the fill factor can enhance performance. A reasonable
rule computing fill factor is to set it to the following:
(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 method configures a database, not only operations performed
using the specified Db handle.
The Db::set_h_ffactor interface may not be called after the Db::open
interface is called.
If the database already exists when
Db::open is called, the information specified to Db::set_h_ffactor will
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.
The Db::set_h_ffactor method may fail and throw an exception or return a non-zero error for the following conditions:
- An invalid flag value or parameter was specified.
Called after Db::open was called.
The Db::set_h_ffactor method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the Db::set_h_ffactor method may fail and
either return DB_RUNRECOVERY or throw a
in which case all subsequent Berkeley DB calls will fail in the same way.
Databases and Related Methods
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