Berkeley DB: DB->set_h_ffactor
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++

# DB->set_h_ffactor |

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    #include <db.h>

    int
    DB->set_h_ffactor(DB *db, 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 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 be ignored.

The DB->set_h_ffactor method returns a non-zero error value on failure and 0 on success.

# Errors

The DB->set_h_ffactor method may fail and return a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

  Called after DB->open was called.

The DB->set_h_ffactor method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the DB->set_h_ffactor method may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DB

# See Also

Databases and Related Methods`

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