1. A computer program product, embodied in a non-transitory computer-readable storage medium, the computer program product being operable to cause at least one data processing apparatus to perform operations comprising: performing block compression for a column of data out of one or more columns of data; storing changes to the column of data after the block compression is performed in a delta buffer, wherein the delta buffer is separate from the column of data; and asynchronously integrating changes stored in the delta buffer into the column of data.