In some embodiments, a query recipient is configured to determine that a database query warrants a first projection operation to project a plurality of input rows to a plurality of projected rows. Each of the input rows has one or more variable-length columns. A projection controller is configured to construct a first projection control block to describe the first projection operation. For this construction, the projection controller is configured to construct a plurality of projection control elements, each one corresponding to a corresponding column in the input rows, and a header to specify the order of the projection control elements. The projection controller is further configured to offload the first projection operation to a hardware accelerator, and to provide the first projection control block to the hardware accelerator, where the first projection control block enables the hardware accelerator to perform the first projection operation at streaming rate.