On Tue, Nov 8, 2011 at 7:08 PM, Gabor Grothendieck <ggrothendi...@gmail.com>wrote:
> On Tue, Nov 8, 2011 at 6:46 PM, Richard Hipp <d...@sqlite.org> wrote: > > On Tue, Nov 8, 2011 at 5:50 PM, Gabor Grothendieck > > <ggrothendi...@gmail.com>wrote: > > > >> In R, the RSQLite driver for SQLite currently has > >> SQLITE_MAX_VARIABLE_NUMBER set to 999. This is used by many people > >> for many different projects and on different platforms and it seems > >> that a number of these projects want a larger number. Users don't > >> compile this themselves so they are stuck with whatever number is > >> compiled in for them. > >> > >> What are the considerations for setting this number? > >> > >> Is there any general advice that can be given on how to set this number? > >> > > > > I just checked and it appears that MacOS Lion compiles it a 500000. > > > > Whenever you use a value like ?N, SQLite allocates an array of N objects, > > each of 72 bytes in size. So doing "SELECT ?500000" on Lion requires a > > 36MB memory allocation (with its accompanying memset()). That's really > the > > only downside to choosing a really large SQLITE_MAX_VARIABLE_NUMBER. > > If "SELECT ?500000" allocates 500000 * 72 bytes of memory then how > does that relate to SQLITE_MAX_VARIABLE_NUMBER? > SQLITE_MAX_VARIABLE_NUMBER did not seem to enter the calculation at > all. > SQLITE_MAX_VARIABLE_NUMBER determines the largest N for which ?N will work. So by default, the maximum allocation is 999*72. You can increase this to whatever you are comfortable with. > > -- > Statistics & Software Consulting > GKX Group, GKX Associates Inc. > tel: 1-877-GKX-GROUP > email: ggrothendieck at gmail.com > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
