Jens, Simon, thanks for your feedback and suggestions. I will take a closer look at keeping a "shadow“ copy in the current location and copy the file to the Documents folder when needed. That seems to be a feasible approach, especially with what Jens wrote about APFS and its copy-on-write support. I’ve completely forgotten that. :-)
Thanks Arno > Am 24.10.2017 um 19:07 schrieb Jens Alfke <j...@mooseyard.com>: > > > >> On Oct 24, 2017, at 8:14 AM, Arno Gramatke <ar...@meyersound.com> wrote: >> >> My first naive approach was to figure out, which commands will result in a >> read and which will result in a write to the db file. > > I think you’ll need to assume that any SQLite access can both read and write > the file. So at a high level, you should use the NSFileCoordinator to request > access before an activity that can cause queries or database writes. > > If you want to avoid requesting write access too often, you could open the > database read-only; then you’d know SQLite would only be reading. When you > need to make a change you could open another handle with write access just > for that transaction. > >> Another idea was to copy the db from the file into an in-memory database >> using file coordination, make all modifications in-memory and then copy the >> in-memory back to the file system. > > Why not copy it on-disk? iOS 10.3 or later has the APFS filesystem, which is > copy-on-write at the block level, making it extremely cheap to copy files. So > the initial copy operation will be nearly instant and consume nearly zero > disk space, and subsequent changes will use space only for the disk blocks > that SQLite changes or adds. Likewise, copying the file back should be > instant too. > > —Jens > _______________________________________________ > 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
