public DBFieldIterator indexKeyIteratorAfter(int columnIndex, Field startField)
			throws IOException {
		synchronized (db) {
			IndexTable indexTable = secondaryIndexes.get(columnIndex);
			if (indexTable == null) {
				throw new IOException("Index required (" + getName() + "," + columnIndex + ")");
			}
			return indexTable.keyIteratorAfter(startField);
		}
	}
Iterate over all primary keys sorted based upon the associated index key.
The iterator is initially positioned after the index buffer whose index key 
is equal to the specified startField value or immediately before the first 
index buffer whose index key is greater than the specified startField value.
@param columnIndex schema column to sort on
@param startField index column value which determines initial position of iterator
@return primary key iterator
@throws IOException thrown if IO error occurs
Ghidra/Framework/DB/src/main/java/db/Table.java