On Wed, Nov 18, 2015 at 11:22:51PM -0700, Keith Medcalf wrote: > On Wednesday, 18 November, 2015 20:36, Nico Williams <nico at > cryptonector.com> said: > > On Thu, Nov 19, 2015 at 12:39:41AM +0000, Simon Slavin wrote: > > > On 19 Nov 2015, at 12:26am, Nico Williams <nico at cryptonector.com> > > > wrote: > > > > two concurrent scans of the same table should be able to go faster > > > > than the same two scans in series. > > > > > SQLite is not processor-bound, it's file-bound. Both > > > threads/processes need to continually read blocks from disk and a disk > > > can only answer one request at a time. > > > Two table scans of the same data in sequence are going to cost more than > > two table scans of the same data concurrently. > > The original was taking about the "same table". "same data" is > somewhat sloppy terminology. Assuming that "same data" == "same
It was sloppy. In fact, it was wrong: it's not the same data because it's a UNION ALL of two queries each of which will be scanning a different table, not the "same data". Nico --
