/**
* Overrides the parent implementation to provide a more efficient mechanism for generating
* primary keys, while generating the primary key support on the fly.
*
* @param count the batch size
* @param entity the entity requesting primary keys
* @param channel open JDBCChannel
* @return NSArray of NSDictionary where each dictionary corresponds to a unique primary key value
*/
public NSArray newPrimaryKeys(int count, EOEntity entity, JDBCChannel channel) {
if (isPrimaryKeyGenerationNotSupported(entity)) {
return null;
}
EOAttribute attribute = (EOAttribute) entity.primaryKeyAttributes().lastObject();
String attrName = attribute.name();
boolean isIntType = "i".equals(attribute.valueType());
NSMutableArray results = new NSMutableArray(count);
String sequenceName = sequenceNameForEntity(entity);
DB2Expression expression = new DB2Expression(entity);
boolean succeeded = false;
for (int tries = 0; !succeeded && tries < 2; tries++) {
while (results.count() < count) {
try {
StringBuffer sql = new StringBuffer();
sql.append("SELECT ");
sql.append("next value for " + sequenceName + " AS KEY");
sql.append(" from sysibm.sysdummy1");
expression.setStatement(sql.toString());
channel.evaluateExpression(expression);
try {
NSDictionary row;
while ((row = channel.fetchRow()) != null) {
Enumeration pksEnum = row.allValues().objectEnumerator();
while (pksEnum.hasMoreElements()) {
Number pkObj = (Number) pksEnum.nextElement();
Number pk;
if (isIntType) {
pk = Integer.valueOf(pkObj.intValue());
} else {
pk = Long.valueOf(pkObj.longValue());
}
results.addObject(new NSDictionary(pk, attrName));
}
}
} finally {
channel.cancelFetch();
}
succeeded = true;
} catch (JDBCAdaptorException ex) {
throw ex;
}
}
}
if (results.count() != count) {
throw new IllegalStateException(
"Unable to generate primary keys from the sequence for " + entity + ".");
}
return results;
}
/**
* Checks whether primary key generation can be supported for <code>entity</code>
*
* @param entity the entity to be checked
* @return yes/no
*/
protected boolean isPrimaryKeyGenerationNotSupported(EOEntity entity) {
return entity.primaryKeyAttributes().count() > 1
|| ((EOAttribute) entity.primaryKeyAttributes().lastObject()).adaptorValueType()
!= EOAttribute.AdaptorNumberType;
}
/**
* Utility method that returns the name of the sequence associated with <code>entity</code>
*
* @param entity the entity
* @return the name of the sequence
*/
protected static String _sequenceNameForEntity(EOEntity entity) {
return entity.primaryKeyRootName() + "_seq";
}
