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public interface SecondaryKeyCreator
The interface implemented for extracting single-valued secondary keys from primary records.
The key creator object is specified by calling
SecondaryConfig.setKeyCreator.
The secondary database configuration is specified when calling
Environment.openSecondaryDatabase.
For example:
class MyKeyCreator implements SecondaryKeyCreator {
public boolean createSecondaryKey(SecondaryDatabase secondary,
DatabaseEntry key,
DatabaseEntry data,
DatabaseEntry result)
throws DatabaseException {
//
// DO HERE: Extract the secondary key from the primary key and
// data, and set the secondary key into the result parameter.
//
return true;
}
}
...
SecondaryConfig secConfig = new SecondaryConfig();
secConfig.setKeyCreator(new MyKeyCreator());
// Now pass secConfig to Environment.openSecondaryDatabase
| Method Summary | |
|---|---|
boolean |
createSecondaryKey(SecondaryDatabase secondary,
DatabaseEntry key,
DatabaseEntry data,
DatabaseEntry result)
Creates a secondary key entry, given a primary key and data entry. |
| Method Detail |
|---|
boolean createSecondaryKey(SecondaryDatabase secondary,
DatabaseEntry key,
DatabaseEntry data,
DatabaseEntry result)
throws DatabaseException
A secondary key may be derived from the primary key, primary data, or a combination of the primary key and data. For secondary keys that are optional, the key creator method may return false and the key/data pair will not be indexed. To ensure the integrity of a secondary database the key creator method must always return the same result for a given set of input parameters.
secondary - the database to which the secondary key will be added.
This parameter is passed for informational purposes but is not commonly
used.
key - the primary key entry. This parameter must not be modified
by this method.
data - the primary data entry. This parameter must not be modified
by this method.
result - the secondary key created by this method.
DatabaseException - if an error occurs attempting to create the
secondary key.
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