public void validate() throws EGQLException {
Set<String> itemNames = newHashSet();
for (InsertItem item : items) {
// duplicate insert item is not allowed
if (itemNames.contains(item.getIdentity())) {
throw new EGQLE050Exception();
} else {
itemNames.add(item.getIdentity());
}
// aggregation function is not allowed in insert statement without select clause