Query Processing and Optimization
Query Processing and Optimization
Query Processing and Optimization
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Partitioning Phase<br />
• Partitioning phase: r divided into n h partitions. The<br />
number of buffer blocks is n B . One block used for<br />
reading r. (n h = n B -1)<br />
• Similar with relation s<br />
• I/O cost: 2 × (b r + b s )<br />
OUTPUT<br />
1<br />
Partitions<br />
Relation<br />
r or s<br />
. . .<br />
INPUT<br />
hash<br />
function<br />
h<br />
2<br />
n B<br />
-1<br />
1<br />
2<br />
n B<br />
-1<br />
Disk<br />
n B<br />
main memory buffers<br />
Disk<br />
21
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