• number of tuples in output

  r_out = | π_a,b,..(T) | = |T| = r_T    (in SQL, because of bag semantics)

• size of tuples in output

  R_out = sizeof(a) + sizeof(b) + ... + tuple-overhead

Assume pages of size B,   b_out = ceil(r_T / c_out),   where c_out = floor(B/R_out)

If using select distinct ...

• | π_a,b,..(T) | depends on proportion of duplicates produced