Contrary to dense fragments, there is no correspondence between space tiles and data tiles in sparse fragments. Consider the
8x8 fragment with
4x4 space tiles in the figure below. Assume for simplicity that the array stores a single
int32 attribute. The non-empty cells are depicted in blue color. If we followed the data tiling technique of dense fragment, we would have to create 4 data tiles, one for each space tile. TileDB does not materialize empty cells, i.e., it stores only the values of the non-empty cells in the data files. Therefore, the space tiles would produce 4 data tiles with 3 (upper left), 12 (upper right), 1 (lower left) and 2 (lower right) non-empty cells.