org.datanucleus.store.rdbms.valuegenerator
Class MaxGenerator

java.lang.Object
  org.datanucleus.store.valuegenerator.AbstractGenerator
      org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator
          org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator
              org.datanucleus.store.rdbms.valuegenerator.MaxGenerator

All Implemented Interfaces:

org.datanucleus.store.valuegenerator.ValueGenerator

public class MaxGenerator
extends AbstractRDBMSGenerator

This generator for Relational Databases uses the "select max(column) from table" strategy. The block size is limited to 1. MaxPoidGenerator works with numbers, so clients using this generator must cast the ID to Long *

Required user properties

Optional user properties

Field Summary

protected static org.datanucleus.util.Localiser

LOCALISER_RDBMS

Fields inherited from class org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator

connection

Fields inherited from class org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator

connectionProvider, storeMgr

Fields inherited from class org.datanucleus.store.valuegenerator.AbstractGenerator

allocationSize, block, initialValue, LOCALISER, name, properties, repositoryExists

Constructor Summary

MaxGenerator(java.lang.String name, java.util.Properties props)
Constructor.

Method Summary

org.datanucleus.store.valuegenerator.ValueGenerationBlock

reserveBlock(long size) Method to reserve a block of identities.

Methods inherited from class org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator

obtainGenerationBlock, requiresConnection

Methods inherited from class org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator

setConnectionProvider, setStoreManager

Methods inherited from class org.datanucleus.store.valuegenerator.AbstractGenerator

allocate, createRepository, current, currentValue, getName, getStorageClass, next, nextValue, obtainGenerationBlock, repositoryExists, requiresRepository, reserveBlock

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOCALISER_RDBMS

protected static final org.datanucleus.util.Localiser LOCALISER_RDBMS

Constructor Detail

MaxGenerator

public MaxGenerator(java.lang.String name,
                    java.util.Properties props)

Constructor.

Parameters:

name - Symbolic name for this generator

props - Properties defining the behaviour of this generator

Method Detail

reserveBlock

public org.datanucleus.store.valuegenerator.ValueGenerationBlock reserveBlock(long size)

Method to reserve a block of identities. Note : Only allocates a single id always.

Specified by:

reserveBlock in class org.datanucleus.store.valuegenerator.AbstractGenerator

Parameters:

size - The block size

Returns:

The reserved block