Restructuring versus Non Restructuring Insertions in MDF Indexes

MDF tree is a data structure (index) that is used to speed up similarity searches in huge databases. To achieve its goal the indexes should exploit some property of the dissimilarity measure. MDF indexes assume that the dissimilarity measure can be viewed as a distance in a metric space. Moreover, in this framework is assumed that the distance is computationally very expensive and then, counting distance computations is a good measure of the time complexity. To tackle with a changing world, a problem arises when new points should be inserted in the index. Efficient algorithms should choose between trying to be efficient in search maintaining the “ideal” structure of the index or trying to be efficient when inserting but worsening the search time. In this work we propose an insertion algorithm for MDF trees that focus on optimizing insertion times. The worst case time complexity of the algorithm only depends on the depth of the MDF tree. We compare this algorithm with a similar one that focuses on search time performance. We also study the range of applicability of each one.