We're using MySQL 5 (don't know off the top of my head what specific release). I don't think a master/slave DB configuration is something we can manage to set up at this point.
Querysets are fetched from the database in chunks, right? I imagine that the select itself is actually quite quick, but do the tables remain locked between chunks? I.e. if the query returns a total of N records and Django fetches N/10 records and then performs a bunch of calculations and saves before returning to the DB for another N/10 records, will the DB be locked during all those calculations/saves? On Nov 24, 4:47 am, Tom Evans <tevans...@googlemail.com> wrote: > On Wed, Nov 23, 2011 at 8:09 PM, Nikolas Stevenson-Molnar > > <nik.mol...@consbio.org> wrote: > > What database are you using? You should be able to find information in > > the documents about the locking behavior for that database. Compare that > > with the operations your running and determine whether they would result > > in an exclusive lock. > > > From your pseudocode, it looks like you're performing a possibly-lengthy > > select, followed by lengthy calculations (not involving database > > operations), and then a (presumably) quick save. AFAIK, databases never > > lock when doing selects, so depending on the nature of your > > calculations, you should be fine. > > MySQL will always lock tables for writes when reading from them. > Therefore, any long running query on a mysql table will result in > updates to that table being locked out. > > The easiest way around this is with hardware. Use a master-slave DB > setup, and perform your long reads on the slave(s), and all your > writes on the master. > > Cheers > > Tom -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
