4 ms·

A typical db may do index scan on disk, which requires several times as many io operations per 8kb (Postgresql/Oracle size) page compared to seq scan. These are

by olavgg 8y ago

A typical db may do index scan on disk, which requires several times as many io operations per 8kb (Postgresql/Oracle size) page compared to seq scan. These are executed with low queue depth.

anarazel 8y ago
OTOH there's concurrency and prefetching logic increasing average queue depth.
- olavgg 8y ago
  Are index scans supposed to be faster with prefetch? It is random read at 8kb. I usually set read_ahead_kb to 8kb on disks/tablespaces for indexes.