Using BigInteger as primarykey

Question

Hi,
When I use BigInteger as primary key and use the sequence with it I get this exception
java.lang.ClassCastException: java.lang.Long
     at com.sleepycat.persist.impl.SimpleFormat$FBigInt.writeObject(SimpleFormat.java:767)
     at com.sleepycat.persist.impl.PersistKeyAssigner.assignPrimaryKey(PersistKeyAssigner.java:50)
     at com.sleepycat.persist.PrimaryIndex.assignKey(PrimaryIndex.java:487)
     at com.sleepycat.persist.PrimaryIndex.put(PrimaryIndex.java:338)
     at com.sleepycat.persist.PrimaryIndex.put(PrimaryIndex.java:314)
SimpleFormat is trying to cast the Long value to bigInteger and thats how the class cast
exception is raised.
My question is can we use bigInteger with the DPL sequence like
@PrimaryKey(sequence="seq_my_entity")
private BigInteger my_pk;
What my understanding is that BigInteger is included in the simple datatypes of the DPL, and it should support the autogeneration of BigInt keys.
One more thing what will happen when primary key having the type long runs out of value, like there are millions of record.
Thanks,
Shoaib

Answer 1

Hello Shoaib,
Primary key sequences are not currently allowed with BigInteger keys. See the javadoc for PrimaryKey.sequence:
http://www.oracle.com/technology/documentation/berkeley-db/je/java/com/sleepycat/persist/model/PrimaryKey.html#sequence()
To use a sequence, the type of the key field must be a primitive integer type (byte, short, int or long) or the primitive wrapper class for one of these types.
We do not currently support BigInteger sequences because (as you point out) JE sequences are limited to long values, and BigInteger can contain much larger values. This limitation is in the JE base API Sequence class, not the DPL.
However, you should have received a more informative error message, not a ClassCastException. We'll fix that in a future release.
If you need values larger than a long, and you would like to assign them from a sequence, you can use a BigInteger key and implement a sequence yourself. I suggesting implementing a singleton sequence class that increments the sequence in memory, in a synchronized method, for example:
private BigInteger lastValue;
synchronized BigInteger getNext() {
    lastValue = lastValue.add(BigInteger.ONE);
    return lastValue;
}When opening the store, initialize the sequence from the largest existing key; for example:
PrimaryIndex<BigInteger,MyData> priIndex = ...
EntityCursor<BigInteger> keys = priIndex.keys();
try {
   lastValue = keys.last();
} finally {
   keys.close();
if (lastValue == null) {
    lastValue = BigInteger.ONE;
}Does this help?
Mark