public int getPropertyId(@NotNull final PersistentStoreTransaction txn, @NotNull final String propertyName, final boolean allowCreate) {
        return allowCreate ? propertyIds.getOrAllocateId(txn, propertyName) : propertyIds.getId(txn, propertyName);
    }
public int getPropertyId ( @ NotNull final PersistentStoreTransaction txn , @ NotNull final String propertyName , final boolean allowCreate ) { return allowCreate ? propertyIds . getOrAllocateId ( txn , propertyName ) : propertyIds . getId ( txn , propertyName ) ; }
Gets id of a property and creates the new one if necessary.

@param txn          transaction
@param propertyName name of the property.
@param allowCreate  if set to true and if there is no property named as propertyName,
create the new id for the propertyName.
@return < 0 if there is no such property and create=false, else id of the property