Xodus unique property key value

Question

Is there a way to make a Entity property unique when storing using PersistentEntityStore?

Such than any put operation with a duplicate property value would translate to a rollback or should not commit. Is this possible?

Answer 1

There is no specific way to declare such an index. If PersistentEntityStore#executeInTransaction() or PersistentEntityStore#computeInTransaction() is used to define a transaction, then one can check if a property is unique directly in the lambda:

entityStore.executeInTransaction(txn -> {
    // ...
    if (!txn.find("EntityType", "propertyName", propValue).isEmpty()) {
        throw new ExodusException("Unique property violation");
    }
    entity.setProperty("propertyName", propValue);
    // ...
});

This way of setting properties can be extracted, for example, to a Kotlin extension function:

fun StoreTransaction.setProperty(entity: Entity, entityType: String, propName: String, propValue: Comparable<*>) {
    if(!find(entityType, propName, propValue).isEmpty) {
        throw ExodusException("Unique property violation: $propName = $propValue")
    }
    entity.setProperty(propName, propValue)
}