From: "Christian Smith" <[EMAIL PROTECTED]> > On Tue, 28 Sep 2004, Kazuho Oku wrote:
> >Unfortunately, my apache module only performs a single SELECT clause of > >which WHERE clause can be indexed. > >What I am wondering is the way to stop calling SQLite each time the module > >processes an HTTP request (eliminate the FLOCK -> READ -> FUNLOCK done by > >SQLite). > > Is this an actual bottleneck? Against internet latencies, this is likely > not to be that big a win. > > It will not be significantly slower than any other filesystem operation, > such as checking for an indicator file, especially if you then remove the > indicator file (synchronous disk operations!) It's not the latency that is the problem. The problem is the performance decrease caused by the module I am developing. When apache (without my module) sends a static file, the disk-related system calls that it issues are: stat(), open(), mmap(), munmap(), write(), once for each. If my module did not cache database information, then it would issue flock() twice, and multiple seek()s and read()s. Although I have not benchmarked, my understanding is that this would be of (at least) some performance penalty. This is the reason why I think caching is necessary. > Does the cache have to be in sync with the current database all the time. > ie. Would it be satisfactory to simply check the database once per second, > and only update the cache then? This would certainly reduce any SQLite > overhead significantly. Since apache is a multiprocess server, I do not think rereading the database periodically is a good idea. Typical usage would be to update the database through a CGI and then access through the updated database from a different HTTP connection. So I cannot make the interval between rereads long.
