1. A processor-implemented method for partitioning a database index, the method comprising: partitioning, by one or more processors, a database index by determining that a first-level index partition stored in a data cache exceeds a threshold size; performing, by the one or more processors, a first-level partitioning operation to write the first-level index partition stored in the data cache to a secondary storage, and generate a new first-level index partition in the data cache; performing, by the one or more processors, a first-level merge operation merging a predetermined number of first-level index partitions into a single second-level index partition, and deleting the predetermined number of first-level index partitions from the secondary storage; receiving, at a processor-implemented query processing module, a query specifying data selection criterion; and utilizing the database index to process the query and to provide, from a database table, records satisfying the data selection criterion.