com.sleepycat.client

Interface SSecondaryMultiKeyCreator

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface SSecondaryMultiKeyCreator

The interface implemented for extracting multi-valued secondary keys from primary records.

The key creator object is specified by calling SSecondaryConfig.setMultiKeyCreator(com.sleepycat.client.SSecondaryMultiKeyCreator). The secondary database configuration is specified when calling SEnvironment.openSecondaryDatabase(com.sleepycat.client.STransaction, java.lang.String, java.lang.String, com.sleepycat.client.SDatabase, com.sleepycat.client.SSecondaryConfig).

For example:

  class MyMultiKeyCreator implements SSecondaryMultiKeyCreator {
      public void createSecondaryKeys(SSecondaryDatabase secondary,
              SDatabaseEntry key,
              SDatabaseEntry data,
              Set<SDatabaseEntry> results) throws SDatabaseException {
          //
          // DO HERE: Extract the secondary keys from the primary key and
          // data.  For each key extracted, create a SDatabaseEntry and add
          // it to the results set.
          //
      }
  }
  ...
  SSecondaryConfig secConfig = new SSecondaryConfig();
  secConfig.setMultiKeyCreator(new MyMultiKeyCreator());
  // Now pass secConfig to Environment.openSecondaryDatabase
 

Use this interface when any number of secondary keys may be present in a single primary record, in other words, for many-to-many and one-to-many relationships. When only zero or one secondary key is present (for many-to-one and one-to-one relationships) you may use the SSecondaryKeyCreator interface instead. The table below summarizes how to create all four variations of relationships.

Key creator for different relationships

Relationship	Interface	Duplicates	Example
One-to-one	SSecondaryKeyCreator	No	A person record with a unique social security number key.
Many-to-one	SSecondaryKeyCreator	Yes	A person record with a non-unique employer key.
One-to-many	SSecondaryMultiKeyCreator	No	A person record with multiple unique email address keys.
Many-to-many	SSecondaryMultiKeyCreator	Yes	A person record with multiple non-unique organization keys.

To configure a database for duplicates, pass true to SDatabaseConfig.setSortedDuplicates(boolean).

Note that SSecondaryMultiKeyCreator may also be used for single key secondaries (many-to-one and one-to-one); in this case, at most a single key is added to the results set. SSecondaryMultiKeyCreator is only slightly less efficient than SecondaryKeyCreator in that two or three temporary sets must be created to hold the results.

Method Summary

Modifier and Type	Method and Description
void	createSecondaryKeys(SSecondaryDatabase secondary, SDatabaseEntry key, SDatabaseEntry data, java.util.Set<SDatabaseEntry> results) Create multiple secondary key entries, given a primary key and data entry.

Method Detail

createSecondaryKeys

void createSecondaryKeys(SSecondaryDatabase secondary,
                         SDatabaseEntry key,
                         SDatabaseEntry data,
                         java.util.Set<SDatabaseEntry> results)
                  throws SDatabaseException

Create multiple secondary key entries, given a primary key and data entry.

A secondary key may be derived from the primary key, primary data, or a combination of the primary key and data. Zero or more secondary keys may be derived from the primary record and returned in the results parameter. To ensure the integrity of a secondary database the key creator method must always return the same results for a given set of input parameters.

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.

results - the set to contain the the secondary key SDatabaseEntry objects created by this method.

Throws:

SDatabaseException - if an error occurs attempting to create the secondary key.