TatukGIS products use R-TREE spatial indexing, which sometimes can result in the database indexes being as big as the data itself. Imagine indexing a one column table if the data in the column is random.
With R-TREE, each element is addressed. An alternative method is the QUADRANGLE method, which is a bit similar to "hashing". The advantage of R-TREE is that it provides faster access, whereas the QUADRANGLE method offers a smaller index file size.