Week 10 Lectures (116)

Query Evaluation in CoDbs (cont)

Example: select a,b,c from R where b>10 and d<7

// Assume: each column contains N values
matches1 = all-zero bit-string of length N
matches2 = all-zero bit-string of length N
for i in 0 .. N-1 {
   if (b[i] > 10) matches1[i] = 1
   if (d[i] < 7) matches2[i] = 1
}
matches = matches1 AND matches2
for i in 0 .. N-1 {
   if (matches[i] == 0) continue
   add (a[i], b[i], c[i]) to Results
}