Methods and systems for partitioning and dynamically merging a database index are described. A database index includes a single first-level index partition stored in a data cache. As the first-level index partition in the data cache reaches a predetermined size, it is copied to secondary storage and a new index partition is generated in the data cache. When the number of index partitions in secondary storage reaches some predetermined number, the index partitions are merged to create a single index partition of a higher level in a hierarchy of index partitions having an exponentially increasing size with each increase in level within the hierarchy.