}
if(lblcol == -1) {
throw new AbortException("No label column found in first source, cannot join (do you want to use " + ExternalIDJoinDatabaseConnection.class.getSimpleName() + " instead?)");
}
for(int i = 0; i < first.dataLength(); i++) {
Object data = first.data(i, lblcol);
if(data == null) {
logger.warning("Object without label encountered.");
continue;
}
if(data instanceof String) {