On 22 Jan 2016, at 4:01am, Rowan Worth <rowanw at dugeo.com> wrote: > To a point I agree, but in reality there's a fixed amount of work involved > with each write transaction. I recently profiled an operation involving > ~75,000 rows that took ~8.5 minutes to complete, and found that 80% of the > time was spent waiting for COMMIT to complete. Rewriting the code so that > all the work happened in a single transaction immediately dropped the > overall time down to ~1.66 minutes.
Nice stats. This is, of course, all about waiting for a rotating disc to be in the right place. 4500 rotations per minute is 75 rotations per second or 13ms per rotation. If a transaction which involves a single row being written involves five write operations then it can take up to 65ms just waiting for the rotating disc. Call it an average of 33ms per transaction. Do that 75,000 times and you're waiting up to 2475 seconds == 40 minutes. No wonder solid state storage speeds things up. Simon.
