Sorry I am missing a bit, What is the problem of using sqlite3_backup again?
On Thu, Jun 6, 2013 at 10:01 AM, Philip Bennefall <phi...@blastbay.com> wrote: > > ----- Original Message ----- From: "Simon Slavin" <slav...@bigfraud.org> > To: <phi...@blastbay.com>; "General Discussion of SQLite Database" > <sqlite-users@sqlite.org> > Sent: Thursday, June 06, 2013 12:15 AM > > Subject: Re: [sqlite] Serialize an in-memory database > > > > On 5 Jun 2013, at 8:38pm, Philip Bennefall <phi...@blastbay.com> wrote: > >> On 5 Jun 2013, at 8:32pm, Petite Abeille <petite.abei...@gmail.com> wrote: >> >>> write to tmpfs… read the file into byte[]… do what you meant to do… to >>> reload… write byte[] do tmpfs… open db… and be merry… or something along >>> these lines... >> >> >> I don't want it in a file, however. I want it in a memory block. > > > That's why you read from tmpfs (or any other file stored in any other file > system) into byte[]. Once your data is in byte[] you will have entire > SQLite database in one run of memory. > > You can't usefully store a memory database of SQLite because SQLite's data > in memory isn't all in one big run of memory. The data is stored in various > little chunks, some here, some there. If you tried to read the data directly > out of those chunks you would have to read lots of little chunks, not one > big run of continuous memory. And you'd be storing lots of pointers to > various locations in memory. When you 'restore' the data back into memory > you're not going to be allocated the same locations in memory so those > pointers won't mean anything any more. > > A database stored in a file, however, has pointers to locations in that file > instead of pointers to locations in memory. If you save and restore the > whole file in one big run, those pointers will become valid again: the same > bits of data will be at the same offsets of the file. > > Doesn't have to be tmpfs. You can use any file system that SQLite thinks is > file storage rather than memory storage. > > Simon. > > Hi Simon, > > Since I don't believe that Windows for example has tmpfs (seems to be a Unix > thing), would the idea of constructing a vfs that just reads and writes a > huge memory block be doable? If so, how difficult of a task do you estimate > that this might be? I want to reuse as much of the existing vfs code as > possible (e.g. I don't want to reimplement randomness, date etc). Could you > possibly give me some pointers? I read the chapter about the virtual file > systems, but it seems incomplete. > > Kind regards, > > Philip Bennefall > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
