public DBFieldIterator indexFieldIterator(Field minField, Field maxField, boolean before,
			int columnIndex) throws IOException {
		synchronized (db) {
			IndexTable indexTable = secondaryIndexes.get(columnIndex);
			if (indexTable == null) {
				throw new IOException("Index required (" + getName() + "," + columnIndex + ")");
			}
			return indexTable.indexIterator(minField, maxField, before);
		}
	}
Iterate over all the unique index field values within the specified range identified
by minField and maxField.  Index values are returned in an ascending sorted order.
@param minField minimum index column value, if null absolute minimum is used
@param maxField maximum index column value, if null absolute maximum is used
@param before if true initial position is before minField, else position
is after maxField
@param columnIndex identifies an indexed column.
@return index field iterator.
@throws IOException thrown if IO error occurs
Ghidra/Framework/DB/src/main/java/db/Table.java