The Key to Performance: Turn 10 Instructions Into 1
When Data is Always in Memory...
- SQL Optimization is Unambiguous
- Data Copying is Eliminated
- Data is Referenced via Memory Addresses
When Data is Mostly on Disk
- SQL Optimization is Biased Toward I/O
- Data is Copied for Every Access
- Data is Referenced via Disk Addresses, which Require Translation into Memory Buffers
On Average, Copying, Indirection, and an I/O Bias Use 10 Times More Instructions Than Necessary