Berkeley DB: Db::set_h_nelem
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_nelem |

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    #include <db_cxx.h>

    int
    Db::set_h_nelem(u_int32_t h_nelem);

    int
    Db::get_h_nelem(u_int32_t *h_nelemp);

### Description: Db::set_h_nelem

Set an estimate of the final size of the hash table.

In order for the estimate to be used when creating the database, the Db::set_h_ffactor method must also be called. If the estimate or fill factor are not set or are set too low, hash tables will still expand gracefully as keys are entered, although a slight performance degradation may be noticed.

The Db::set_h_nelem method configures a database, not only operations performed using the specified Db handle.

The Db::set_h_nelem method may not be called after the Db::open method is called. If the database already exists when Db::open is called, the information specified to Db::set_h_nelem will be ignored.

The Db::set_h_nelem 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.

### Parameters

h_nelem
  The h_nelem parameter is an estimate of the final size of the hash table.

### Errors

The Db::set_h_nelem method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  If the method was called after Db::open was called; or if an invalid flag value or parameter was specified.

### Description: Db::get_h_nelem

The Db::get_h_nelem method returns the estimate of the final size of the hash table.

The Db::get_h_nelem method may be called at any time during the life of the application.

The Db::get_h_nelem 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.

### Parameters

h_nelemp
  The Db::get_h_nelem method returns the estimate of the final size of the hash table in h_nelemp.

### Class

Db

### See Also

Databases and Related Methods`

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