On Thu, May 01, 2003 at 10:31:06PM +0200, Luc Van Oostenryck wrote:
On Thu, May 01, 2003 at 02:47:35PM -0500, Lee Daniel Crocker wrote:
Along those lines, I'd like to ask for some feedback: if I do the Bloom filter in shared memory thing, I can choose parameters to optimize things. So here's the first question: Bloom filters have no false negatives (that is, there's no risk that they'll show an existing page as non-existing), but there are false positives. What is an acceptable false-positive rate? With a 16-bit filter, the rate will be one in 65,000; I think that's a bit too high. With a 32-bit filter, it's one in 4 billion, which seems reasonable. 24 bits is one in 16 million, which might also be OK.
If all the content of CUR is moved to/duplicat as a filesystem, like David Wheeler suggest it (and a agree completly with him), you don't need the Bloom filter, the filesystem will do the work.
Actually, I think the best win would come from having OLD on the filesystem. CUR would be excellent, too. As it is, OLD has complete copies of every edit ever made, and it forces MySQL to consume an unholy amount of memory. :(