Hi!
I found out that you can implement a user-defined aggregate function with
TWO parameter, e.g. first with the value searched for and the second for
ordering, e.g.
SELECT FIRST(name, id) and an implementation for Integer for value and sort
type like this:
package myh2;
public class First implements org.h2.api.AggregateFunction {
int count = 0;
int result;
int 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;
int value = (Integer) objects[0];
int sort = (Integer) objects[1];
//int sort = (java.lang.Comparable<Integer>) objects[1];
if (count == 0) {
result = value;
order = sort;
} else {
if (sort <= order) {
result = value;
order = sort;
}
}
count++;
}
@Override
public Object getResult() throws java.sql.SQLException {
return result;
}
}
This may be a bad-looking code, sorry, but it should work like that.
In this example the type for the search value and sorting is hard coded as
Integer. Now I look for a more general solution.
--
You received this message because you are subscribed to the Google Groups "H2
Database" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/h2-database.
For more options, visit https://groups.google.com/d/optout.
