On Tue, Nov 8, 2011 at 7:11 PM, Richard Hipp <d...@sqlite.org> wrote: > 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. >
Thanks. So there is really no downside to making it 10,000, say? Those who want it that large will be able to have that many columns and those who don't need that many won't incur any penalties. Is that right? -- 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
