1. A computer-implemented method of processing events, wherein an event includes multiple fields, the method comprising: receiving a set of events; generating a row-based chunk that includes the set of events and metadata about the set of events, wherein the row-based chunk is associated with a first retention policy; generating a column-based chunk that includes metadata about the set of events and, for each event in the set of events, a value of a first field of the multiple fields, wherein the column-based chunk is associated with a second retention policy different from the first retention policy, and wherein the metadata about the set of events in the column-based chunk includes at least one of a minimum value or a maximum value of values of the first field over the events in the set of events; reclaiming storage used by a file containing the row-based chunk according to the first retention policy; and reclaiming storage used by a file containing the column-based chunk according to the second retention policy.