For me it works fine now:
package code.lib.h2;
public class First implements org.h2.api.AggregateFunction {
int count = 0;
Object result;
Object order;
@Override
public void init(java.sql.Connection cnctn) throws java.sql.SQLException
{
// I ignored this
}
@Override
public int getType(int[] ints) throws java.sql.SQLException {
if (ints.length != 2) {
throw new java.sql.SQLException("The aggregate function FIRST
must have 2 arguments.");
}
return ints[0];
}
@Override
public void add(Object o) throws java.sql.SQLException {
Object[] objects = (Object[]) o;
Object value = objects[0];
Object sort = objects[1];
if (count == 0) {
result = value;
order = sort;
} else {
if (((java.lang.Comparable<Object>) sort).compareTo((java.lang.
Comparable<Object>) order) < 0) {
result = value;
order = sort;
}
}
count++;
}
@Override
public Object getResult() throws java.sql.SQLException {
return result;
}
}
package code.lib.h2;
public class Last implements org.h2.api.AggregateFunction {
int count = 0;
Object result;
Object order;
@Override
public void init(java.sql.Connection cnctn) throws java.sql.SQLException
{
// I ignored this
}
@Override
public int getType(int[] ints) throws java.sql.SQLException {
if (ints.length != 2) {
throw new java.sql.SQLException("The aggregate function FIRST
must have 2 arguments.");
}
return ints[0];
}
@Override
public void add(Object o) throws java.sql.SQLException {
Object[] objects = (Object[]) o;
Object value = objects[0];
Object sort = objects[1];
if (count == 0) {
result = value;
order = sort;
} else {
if (((java.lang.Comparable<Object>) sort).compareTo((java.lang.
Comparable<Object>) order) >= 0) {
result = value;
order = sort;
}
}
count++;
}
@Override
public Object getResult() throws java.sql.SQLException {
return result;
}
}
and in the H2 console:
DROP AGGREGATE IF EXISTS FIRST;
CREATE AGGREGATE FIRST FOR "code.lib.h2.First";
DROP AGGREGATE IF EXISTS LAST;
CREATE AGGREGATE LAST FOR "code.lib.h2.Last";
Suggestions for better code are welcome! (I'm no Java programmer, normally
I use Scala.)
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