Operating a database system comprises: storing a database table comprising a plurality of rows, each row comprising a key value and one or more attributes; storing a primary index for the database table, the primary index comprising a plurality of leaf nodes, each leaf node comprising one or more key values and respective memory addresses, each memory address defining the storage location of the respective key value; creating a new leaf node comprising one or more key values and respective memory addresses; performing a memory allocation analysis based upon the lowest key value of the new leaf node to identify a non-full memory page storing a leaf node whose lowest key value is similar to the lowest key value of the new leaf node; and storing the new leaf node in the identified non-full memory page.