public RecordIterator indexIterator(int columnIndex) throws IOException {
		synchronized (db) {
			IndexTable indexTable = secondaryIndexes.get(columnIndex);
			if (indexTable == null) {
				throw new IOException("Index required (" + getName() + "," + columnIndex + ")");
			}
			return new KeyToRecordIterator(this, indexTable.keyIterator());
		}
	}
Iterate over the records using a secondary index.  Sorting occurs on the
specified schema column.  This table must have been constructed with a secondary
index on the specified column.
@param columnIndex schema column to sort on.
@return RecordIterator record iterator.
@throws IOException if a secondary index does not exist for the specified
column or an I/O error occurs.
Ghidra/Framework/DB/src/main/java/db/Table.java