Yes, I think you’re right. I suppose maybe it recognises the desc sequence from page access.
________________________________ From: sqlite-users <sqlite-users-boun...@mailinglists.sqlite.org> on behalf of Andy Ling <andy.l...@s-a-m.com> Sent: Thursday, May 31, 2018 3:57:27 PM To: 'SQLite mailing list' Subject: Re: [sqlite] This is driving me nuts > While that makes sense Clemens it again fails to explain why it does no > caching when desc is stepped through first. I am at least satisfied that it’s > not > something I should dwell on or, more the point, it isn’t down to a bug in my > code which is why I got embroiled in it in the first place. > My understanding from what Clemens said, which might clarify. When ascending pages are read sequentially, so sequential mode is used and the pages get saved in the cache, but when descending, pages are read in reverse order which makes the cache think it's random so it doesn't keep them. So if you do ascending first the cache gets filled and eats up memory. Then when you do descending it gradually deletes all the pages from the cache and frees up the memory. If you do it the other way round, descending uses one page worth of memory then ascending eats up enough for all the pages. Andy Ling --------------------------------------------------------------------------------------- This email has been scanned for email related threats and delivered safely by Mimecast. For more information please visit http://www.mimecast.com --------------------------------------------------------------------------------------- _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
